Note: Descriptions are shown in the official language in which they were submitted.
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FL~ME RETARDA~T RIGID THERMOPLASTIC FOAMS
The present invention relates to high perform-
ance flame retardant rigid thermoplastic foams having
outstanding flame resistance as evidenced by low radiant
panel test values. More particularly, the present inven-
tion relates to shaped foamed blends of dichloroethylene
bisphenol polycarbonate and high performance thermoplastic
organic polymer.
Prior to the present invention, rigid thermo-
plastic foam having high impact strength, such as poly-
carbonate foam has become recognized by the plastics
industry as an attractive material with many valuable uses.
High performance rigid thermoplastic foam, for example, is
being used as a substitute for many light weight metals,
such as aluminum, in the automotive industry for making
automobile roof tops and in the electronics industry as
housing for electronic components. Rigid thermoplastic
foams have become increasingly attractive to the electronic
data processing industry as a substitute for metal because
of the ease of fabrication of thermoplastic foam parts by
conventional injection molding techniques as compared to
the fabrication of metal parts which have to be stamped
out and machined. Although rigid thermoplastic foam has
many attractive features as compared to light weight metal,
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such as aluminum, because of ease of fabrication, stringent
flame retardant requirements have limited the use of high
performance rigid thermoplastic foam as housing for certain
electronic components, such as computers. A test which
has been applied by industry to screen rigid thermoplastic
foam based on flammability evaluation, is the radiant
panel test ASTM-E-162-67.
In accordance with the test, an increase in the
"Is value" which hereinafter will indicate the radiant
panel test value, indicates a reduction in flame retarda-
tion. Experience has shown that the flame retardant
qualities of thermoplastics often are substantially reduced
when the thermoplastic is converted to a rigid cellular
foam. As a result, efforts to improve the flame retardant
properties of rigid cellular foams have been generally
based on the approach of improving the flame retardant
properties of the original thermoplastic source material
and then converting it to the cellular state. For example,
when a bisphenol-A polycarbonate foam panel was evalu-
ated in the above described ASTM test, its "Is value" was
found to be at least twice as great as compared to a bis-
phenol-A polycarbonate panel of the same thickness. The
same result was observed when conventional flame retardant
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materials were added to the polycarbonate which, in the
unfoamed state, produced a satisfactory radiant panel
test value. However, when the same polycarbonate formulation
was converted to a rigid foam, its "Is value" was
greater than 15 which failed the requirements of the electronic
data processing industry as defined by UL Bulletin 484.
As a result, the market potential for flame retardant
rigid thermoplastic foam has been severely restricted
because the foaming process inherently appeared to convert
the thermoplastic to an unacceptable flame retardant
material even though its strength to weight ratio and
ease of fabrication were highly attractive.
The present invention is based on the discovery
that certain dichloroethylene bisphenol polycarbonates
and blends of such materials with particular high performance
thermoplastic polymers can be converted to shaped
flame retardant rigid thermoplastic foams exhibiting
spectacular flame retardant properties. Surprisingly,
the Is values of these rigid thermoplastic foams are either
the same as or not significantly greater than the Is
values of the original high performance
precursor thermoplastic material used in making such foams.
B
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There is provided by the present invention, shaped
flame retardant rigid thermoplastic foams having a density
of from 0.5 g/cc to 1.2 g/ec, and a Gardner impact strength
of at least 10 ft-lbs, which is the product obtained by
the injection foam molding of a melt of a material com-
prising by weight,
(A) at least about 5% of a thermoplastic poly-
earbonate having an intrinsic viscosity of at least 0.35
dl/g and eonsisting essentially of chemically combined
units of the formula
-R-C-Rl- O -C - O -
(1) "
X/ \
and eorrespondingly
(B) up to about 95% of a thermoplastie polymer
seleeted from the elass eonsisting of polyearbonate, poly-
arylene oxide, polyalkyleneterephthalate, polyvinylaromatie
and polyolefin, where R and Rl are divalent aromatie radieals
having from 6-13 earbon atoms, X is a halogen atom, and
X is seleeted from X and hydrogen.
Ineluded by R and Rl of formula 1, are for example,
phenylene, xylylene, diehlorophenylene, tolylene, naphthal-
ene, ete. Radieals ineluded by X are, for example, ehlorine,
bromine, ete.; R and Rl and X and Xl ean be the same or
different radicals respeetively.
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The polycarbonates consisting essentially of
chemically combined units of formula (1) "or haloethylene
polycarbonate", can be made by standard procedures involv-
ing for example, the phosgenation of a haloethylene bis-
phenol of the formula
(2) HO-R -C-R-OH
/c\
where R, Rl, X and ~1 are as previously defined. The bisphenols
of formula (2) can be made by procedures described in
S. Porejko and Z. Wielgosz, Polimery, 13, 55 (1968).
Preferably, the haloethylene polycarbonate has an intrinsic
viscosity in the range of between 0.4 to 0.65 dl/g.
In addition to 1,1-bis(p-4-hydroxyphenyl)-2,2-
dichloroethylene, the haloethylene bisphenols of formula
(2) also include
H()~ ~OH
~C~
Cl Cl
OH 1 1 OH
Cl ~ ~ 1
Cl Cl
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OH OH
, etc.
Br Br
- In addition to the above described haloalkylene
polycarbonate, and blends thereof with thermoplastic
organic material, the flame retardant foams of the present
invention also can be made from copolymers by phosgenating
mixtures of bisphenols of formula (2) with bisphenols
of the formula,
(3) HO-Z-OH
2 2 2 2
where Z is selected from R and R -Q-R , R is selected
from R radicals and Q is selected from,
,R3
R3
divalent cycloaliphatic radicals, oxyaryleneoxy radicals, :
sulfonyl, sulfinyl, oxy, thio, fluorenyl, phenolphthalein
and R3 is selected from C(l 8) alkyl, R and halogenated
derivatives. Typical of the bisphenols of formula 3 are,
for example, 2,2-bis(4-hydroxyphenyl)propane (Bisphenol-A);
2,4-dihydroxydiphenylmethane; bis(2-hydroxyphenyl)methane;
bis(4-hydroxyphenyl)methane; 1,1-bis(4-hydroxyphenyl)ethane;
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1,2-bis(4-hydroxyphenyl)ethane; 1,1-bis(4-hydroxy-2-chloro-
phenyl)ethane; l,l-bis(2,5-dimethyl-4-hydroxyphenyl)ethane,
1,3-bis(3-methyl-4-hydroxyphenyl)propane; 2,2-bis(3-iso-
propyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)
hexylfluoropropane, etc. In addition, 4,4'-sec-butylidene-
diphenol, 4,4'-methylene(2,6-ditert-butylphenol), 2,2'-
methylene(4-methyl-6-tert-butylphenol), bis(4-hydroxy-
phenyl)phenylmethane, bis(4-hydroxyphenyl)cyclohexyl methane,
1,2-bis(4-hydroxyphenyl)-1,2-diphenyl ethane, etc. In add-
ition to the above bisphenols there are also included
within the scope of the dihydroxy compounds of Formula 3
dihydroxybenzenes such as hydroquinone resorcinol, etc.,
4,4'-dihydroxydiphenyl, 2,2'-dihydroxydiphenyl, 2,4'-di-
hydroxydiphenyl, etc.
The "haloalkylene polycarbonate copolymers" can
consist essentially of from about 5 mol percent to about
99 mol percent of formula (1) units and from about 1 mol
percent to 95 mol percent of units of the formula,
(4) 0
-OZOCO-
where Z is as previously defined. Phosgenation of the
mixture of bisphenols of formulas 2 and 3 can be effected
by standard procedures in the presence of an acid acceptor
such as calcium oxide, sodium hydroxide, etc.
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The haloalkylene polycarbonate of the present
invention also can be blended with one or more high per-
formance thermoplastic polymers, such as polycarbonates,
for example, polymers derived from phosgenating formula 3
bisphenols, such as bisphenol fluorenone, etc.; polyphenyl-
ene oxides, polyalkyleneteraphthalates, for example, poly-
ethyleneteraphthalate, polybutyleneteraphthalate, etc.;
polyolefins, for example, polyethylene, polypropylene,
ethylene-propylene copolymers, etc.; and high impact
polystyrene, etc. Some of these blends are described in
Infra-red Spectroscopic Investigation of Polycarbonates,
Z. Wielgosz, Z. Boranowska and K. Janicka, Plaste and
Kautschuk, 19 (12), 902-904 (1972). The blends of the
dihaloethylene polycarbonates with the aforementioned
thermoplastic polymers can be readily achieved by standard
melt extrusion techniques preferably a blend of from 30%
to 99% of the dihaloethylene polycarbonate is made with
from 70% to 1% of polycarbonate. The polycarbonates which
can be employed, for example, are 140 grade LexanR poly-
carbonate of the General Electric Company. In addition
blends of the dihaloethylene polycarbonate can be made
with General Electric Noryl resin, or General Electric
ppoR resin, where there can be utilized from 20% to 95%
of the dihaloethylene polycarbonate. In addition, 20%
to 95% of the dihaloalkylene polycarbonate can be blended
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with from 80% to 5% of polyalkylene terephthalate resins,
for example, polybutylene terephthalate or polyethylene
terephthalate, etc. In addition to the aforementioned
thermoplastic polymers, the dihaloalkylene polycarbonates,
or blends thereof, can be further blended with from 2%
to 60% by weight of glass fiber, and preferably from 4%
to 25% by weight of glass fiber based on the total weight
of thermoplastic polymer and glass fibers in the blend.
In addition to glass fiber, other fillers can be used, such
as clay, glass spheres, silica, barium carbonate, silicon
carbide whiskers, etc.
In the practice of the invention, the dihaloalkyl-
ene polycarbonate which hereinafter will signify polycarbon-
ate consisting essentially of units of formula (1), or a
mixture of units of formulas (1) and (3), or blends of
such dihalo alkylene polycarbonate with other thermoplastic
polymers as previously identified, or the blends of such
thermoplastic material with a glass fiber and/or other
fillers can be blended with a blowing agent by standard
procedure in the form of a dry powder, in an extruded
pelletized form, in the form of an extruded thermoplastic
sheet, etc., based on the melt characteristics of the
thermoplastic polymer or blend and the decomposition
temperature of the blowing agent. In instances where the
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decomposition temperature of the blowing agent is below or
about the temperature at which the blends with the dihalo-
alkylene polycarbonate can be melt extruded, it is preferred
to make the resulting thermoplastic blend in the form of
a dry powder. Blowing agents exhibiting maximum decomposi-
tion rates at temperatures at least 25 greater than the
melt extrusion temperature of the dihaloalkylene polycarbon-
ate can provide for extrudable foamable blends or concen-
trates which can be readily pelletized. Preferably, the
blowing agents used in making the foams of the present
invention are the dihydrooxidiazinones, as taught in my
United States Patent Number 4,097,425, dated
June 27, 1978 and assigned to the same assignee as
the present invention. In instances where the foamable
blend can be pelletized to concentrates having from about
1% to 25% by weight or more of the blowing agent based
on the total weight of blend, it can be further melt extruded
with additional dihaloalkylene polycarbonate to make the
thermoplastic foam of the present invention.
In addition to the above described dihydrooxi-
diazinones, other blowing agents which can be used in com-
bination with the dihaloalkylene polycarbonate are, for
example, 5-phenyltetrazole and diisopropylhydrazodicar-
boxylate. In addition to convention blowing agents, foaming
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of the dihaloalkylene polycarbonate can be achieved by
direct use of inert gases, such as nitrogen by a procedure
described by Angel patent 3,436,446. Injection molding
of the dihaloalkylene polycarbonates of the present inven-
tion can be performed by standard techniques. The afore-
mentioned blowing agents or other conventional means of
blowing to produce shaped foam structures at temperatures
in the range of between 470F to 650E. Included by the
shaped foam structures having flame retardant properties
which can be melt extruded are, for example, computer
housing parts, electrical appliances, business machine
housings, automobile roof tops, food handling equipment,
furniture parts, etc.
In order that those skilled in the art will be
better able to practice the invention, the following
examples are given by way of illustration and not by way
of limitation. A11 parts are by weight.
Example 1.
A mixture of 26.25 parts of 1,1-dichloro-2,2-
bis(4-hydroxyphenyl)ethylene, .026 part of sodium gluconate,
0.237 part of phenol, 0.142 part of triethylamine,
123 parts of methylene chloride and about 75 parts
of water is stirred for about 10
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minutes at a temperature of about 28C. There is then
added to the mixture, an aqueous sodium hydroxide solution
in an amount to adjust the pH of the aqueous phase of the
mixture to approximately 10.
While the mixture is being thoroughly agitated,
phosgene is introduced at a rate of about 12.24 parts per
hour while a 20~ aqueous sodium hydroxide solution is
added in an amount sufficient to maintain the pH of the
aqueous phase of the mixture at 10. Phosgenation of the
mixture is continued for about 3/4 of an hour under these
conditions and then the rate of phosgenation is reduced
to about 6.8 parts per hour while maintaining the pH of the
! aqueous phase to a range of about 11 to 11.5. The phosgen-
ation of the mixture is then continued for about 50
minutes.
The above reaction mixture is then diluted with
about 100 parts of methylene chloride, and washed alterna-
tively with dilute hydrochloric acid, dilute sodium
hydroxide and water. The mixture is then centrifuged and
filtered and thereafter steam precipitated. There is
obtained 26 pounds of product after the precipitate is
recovered and dried at 80C. Based on method of pre-
paration, the product is l,l-dichloro-2,2-bis(4-hydroxy-
phenyl)ethylene polycarbonate having an intrinsic viscosity
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of 0.51 dl/gm in chloroform at 25C.
The above described dichloroethylene polycarbon-
ate is blended with 5-phenyl-3,6-dihydro-1,3,4-oxidiazin-2-
one and glass fiber to produce a blend having .5% by weight
of blowing agent and 5~ by weight of glass fiber. The
mixture is then melt extruded into pellets at 500F.
In accordance with ASTM-E-162-67, 6" x 18" x 1/4"
test panels are prepared by foam molding the above blend from
the above described pellets at 575F. This material has a
Gardner Impact Value of about 25-37.5 ft-lb, an intrinsic --
viscosity of 0.34 dl/gm, and a density of about 1.07. Equi-
valent test panels are also prepared from a blend of the
above described dichloroethylene polycarbonate and 5~ by
weight of glass fiber free of blowing agent. The test panels
are then used in evaluating the flame retardant properties
of the glass filled dichloroethylene polycarbonate and the
rigid foam derived therefrom in accordance with ASTM-E-162-67.
It is found that the unfoamed test panel has an Is value of
0 which is equivalentto asbestos. The foamed panel is
found to have an Is value of 0.8 indicating the foaming of
the original dichloroethylene polycarbonate glass fiber
blend does not significantly reduce the flame retardant
properties of the original blend.
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Example 2
A blend is prepared of about equal parts by weight
of the dichloroethylene polycarbonate of Example 1 and a
Bisphenol-A polycarbonate having an intrinsic viscosity of
about 0.55 dl/g in chloroform at 25C, along with 5% by weight
of the total of glass fiber and 0.5% by weight of the blow-
ing agent of Example 1. The blend is melt extruded into
pellets at 500F. Pellets are also prepared from the same
blend free of blowing agent.
A 6" x 18" test panel is prepared following the
procedure of Example 1 by foam molding the blend at 600F.
The foamed blend has an Is value of 3.9 which is substan-
tially equivalent to the 3.7 value for the unfoamed blend.
The foamed blend also has an intrinsic viscosity of
about 0.45 dl/g in chIoroform at 25C, a Gardner Impact
Value greater than 50 ft-lb and a density of about 1.
Example 3.
A blend is prepared of 20 parts of the dichloro-
ethylene polycarbbnate of Example 1 and 80 parts of the
Bisphenol-A polycarbonate of Example 2 along with 5% by
weight of the total of glass fiber.
A melt of the above blend is processed at 575F
in the extruder of a Springfield Case structural foam mold-
ing machine using nltrogen gas at 1500 psig. The melt is
injected in about 0.08 sec. in a 6" x 18" x 1/4" cavity
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maintained at about 200F. A 75 sec. cycle cool down time
is required. There is obtained a 6" x 18" x 1/4" foam
test panel having an Is value of 6 which is substantially
the same as the Is value of the unfoamed blend. The
density of the foam is 1.05; it has an intrinsic viscosity
of 0.51 and a Gardner Impact of greater than 75.
Example 4
A blend of 75 parts of the dichloroethylene
polycarbonate of Example 1 and 25 parts of an ABS resin is
pelletized at 500F with .5~ by weight of the blend of
the blowing agent of Example 1, and 5% by weight of glass
fiber.
r~est panels are prepared by foam molding the
blend at 575F. A comparison of Is values between foamed
and unfoamed 6" x 18" x 1/4" test panels in accordance
with ASTM-E-162-67 shows a 12.0 for the unfoamed panel and
a 12.5 for the foamed panel.
Example 5.
A mixture of 1,1-dichloro-2,2-bis(4-hydroxy-
phenyl)ethylene and 2,2-bis(4-hydroxyphenol)propane
(Bisphenol-A) is phosgenated in accordance with the pro-
cedures of Example 1. There is used 13.12 parts of the
dichloroethylene bisphenol and 10.65 parts of Bisphenol-A.
There is obtained a copolymer consisting essentially of
chemically co~bined dichloroethylene bisphenol units and
Bisphenol-A units.
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The above-described copolymer is pelletized
with 5-phenyl-3,6-dihydro-1,3,4-oxidiazin-2-one and glass
fiber as in Example 1.
It is found that the Is value of the unfoamed panel
is 3.8 while the foamed panel has an I of 4Ø
Although the above examples are limited to only
a few of the very many shaped foamed articles which can be
made in accordance with the practice of the present inven-
tion, it should be understood that the materials used in
making such foams can vary widely with respect to the
nature of the haloethylene polycarbonate, the thermoplastic
polymer used in combination thereof, or the copolymer
having chemically combined units of formula 1 and units
of the formula,
o
-O-Z-O-C-
where Z is as previously defined. In addition, the means
for converting such thermoplastic material under melt
foaming conditions also can vary widely based on the
nature of the foaming agent employed, such as an oxadiazin-
one, inert gas, etc.
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