Note: Descriptions are shown in the official language in which they were submitted.
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MD-94-09-PO/
M D-94-1 0-PO
FLAME RETARDANT MOLDING
COMPOSITIONS HAVING IMPROVED FLOW
Field of the Invention:
The invention concerns thermoplastic molding compositions and,
in particular, compositions containing polycarbonate and a phosphorous
compound.
SUMMARY OF THE INVENTION
Thermoplastic molding compositions containing a polycarbonate
resin and a phosphorous compound characterized in their improved melt
flow are disclosed. Accordingly, the spiral flow and melt flow index of the
resin is greatly enhanced upon the incorporation of an additive amount of
a phosphorous compound conforming to
O O
Ar-O- IP [-O-(residue)-O--IP ]n O-Ar
O-Ar O-Ar
where -(residue)-, n and Ar are defined. An embodiment characterized by
its flame retardance is also disclosed.
BACKGROUND OF THE INVENTION
Phosphorous containing compounds have long been recognized
for their efficacy as flame retarding agents and thermal stabilizers in
thermoplastic molding compositions, including polycarbonate molding
compositions. Patents relating to this technology include U.S. Patent
4,111,899 which disclosed compounds having P to P bonds as thermal
and oxygen stabilizers of thermoplastic resins. The flame retarding
efficacy of triaryl phosphates in the context of a polymeric resin was
disclosed in U.S. Patent 4,526,917; the utility of other phosphorous
compounds as flame retardant agents for polymers was disclosed in U.S.
ks1\1 021 94
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Patent 5,130,452. Flame retardant thermoplastic compositions containing
a mixture of carbonate polymer, a styrene copolymer and/or a graft
rubber polymer, polytetraflouroroethylene and a phosphorous compound
were disclosed in U.S. Patents 4,751,260, 4,914,144 and 5,234,979.
5 Also relevant is U.S. Patent 5,204,394 which disclosed a flame retardant
blend containing an oligomeric phosphate. A plasticized composition
containing a polycarbonate resin and tetra(lower alkaryl)p-phenylene
diphosphate was disclosed in U.S. Patent 5,122,556.
DETAILED DESCRIPTION OF THE INVENTION
Spiral flow in the context of the composition is a well recognized
term of art. A description of spiral flow molding may be found in Iniection
Moldinq TheorY and Practice, A Wiley-lnterscience Publication, John
Wiley & Sons by Irvin 1. Rubin, PP. 232-233; also in "Spiral Flow
Molding", by L. Griffith in Modem Plastfcs, August, 1957. The spiral flow
15 measurements in the course of the work leading up to the present
invention were made by using a variable thickness spiral flow tool (set at
0.100") in a 3 oz. molding machine. Molding conditions were as follows:
Primary Pressure 18,000 psi
Secondary Pressure 10,000 psi
Back Pressure 800 psi
Screw Speed 100 rpm
Injection Speed 4 inches/second
Cushion 0.250"
Mold Temperature 155F
Melt Temperature 490F
Melt flow rate in the present context is determined in accordance
with ASTM D-1238 at 250C with a 5 kg. Ioad.
The invention resides in the enhanced spiral flow and/or melt flow
rate of the composition. The composition of the invention exhibits a
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considerable improvement, at least about 16% in terms of spiral flow over
that of the unmodified resin; alternatively, the improvement in terms of
melt flow index is about 60% over the unmodified resin.
The thermoplastic composition of the invention contains
5 (i) polycarbonate resin and (ii) an additive amount preferably about 5 to
30 percent by weight of a phosphorous compound conforming to
O O
Il 11
Ar-O-P [--O-(residue)-O--P ]n--O-Ar
O-Ar O-Ar
10 where n is about 1 to 7, preferably about 1 to 3, Ar is an aryl group,
preferably a phenyl group and -(residue)- denotes the residue of a
specific dihydroxydiaryl or a diglycol from which the hydrogen atoms of
the OH groups have been removed. Among the suitable dihydroxydiaryl
compounds are the ones conforming to formulae (I) and (Il)
R5 R5 (I)
HO~ OH
R1 R1 (I l)
HO~ ( C ) ~ OH,
F~2 R3
wherein
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A is a single bond, C1-C5-aikylene, C2-C5-alkylidene, C5-C6-
cycloalkylidene, -0-, -S- or-S02-,
R5 and R6 independently of one another represent hydrogen methyl or
halogen, in particular methyl, chlorine or bromine,
R1 and R2 independently of one another represent hydrogen, halogen,
preferably chlorine or bromine, C~-C8-alkyl, preferably
methyl or ethyl, C5-C6-cycloalkyl, preferably cyclohexyl, C6-
C,0-aryl, preferably phenyl, or C7-C12-aralkyl, preferably
phenyl-C,-C4-alkyl, in particular benzyl,
m is an integer from 4 to 7, preferably 4 or 5,
R3 and R4 can be individually selected for each X and independently of
one another denote hydrogen or C~-C6-alkyl and
X denotes carbon.
The diglycol suitable in the invention has 1 to 30 carbon atoms,
15 preferably 2 to 15 carbon atoms.
Especially suitable phosphorous compounds are bisphenol-A
bisdiphenylphosphate which conform to
O
PHO--! _ O~+<~}O--P--OPH
OPH OPH n=1-7
and neopentyl glycol bis(diphenyl phosphate) conforming to
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O CH3 O
11 11
PHO--Pl OCH2 C CH2-- P OPH
OPH CH3 OPH
The amount of phosphorous compound added to the
5 polycarbonate resin is that amount which imparts to the composition an
improved degree of spiral flow and melt flow. More preferably, the
amount added is about 1 to 15 percent, more preferably, about 5 to 15
percent of the phosphorous compound relative to the weight of the
polycarbonate composition.
Aromatic polycarbonates within the scope of the present invention
are homopolycarbonates and copolycarbonates and mixtures thereof.
The polycarbonates generally have a weight average molecular
weight of 10,000-200,000, preferably 20,000-80,000 and their melt flow
rate, per ASTM D-1238 at 300C, is about 1 to about 65 9/10 min.,
15 preferably about 2-15 9/10 min. They may be prepared, for example, by
the known diphasic interface process from a carbonic acid derivative
such as phosgene and dihydroxy compounds by polycondensation (see
German Oflenlegungsschriften 2,063,050; 2,063,052; 1,570,703;
2,211,956; 2,211,957 and 2,248,817; French Patent 1,561,518; and the
20 monograph H. Schnell, "Chemistry and Physics of Polycarbonates",
Interscience Publishers, New York, New York, 1964, all incorporated
herein by reference).
In the present context, dihydroxy compounds suitable for the
preparation of the polycarbonates of the inventor conform to the
25 structural formulae (1) or (2).
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(1)
H0 ~ (A)~9 H0
(Z)d
(2)
H0 H0
(Z), (Z)f
wherein
10 A denotes an alkylene group with 1 to 8 carbon atoms, an alkylidene
group with 2 to 8 carbon atoms, a cycloalkylene group with 5 to 15
carbon atoms, a cycloalkylidene group with 5 to 15 carbon atoms, a
carbonyl group, an oxygen atom, a sulfur atom, -S0- or -S02- or a
radical conforming to
1 5 ICH3
CH,~ cCH3
e and g both denote the number 0 to 1; Z denotes F, Cl, Br or C~-C4-
20 alkyl and if several Z radicals are substituents in one aryl radical, they
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. 2157082
may be identical or different from one another; d denotes an integer offrom 0 to 4; and f denotes an integer of from 0 to 3.
Among the dihydroxy compounds useful in the practice of the
invention are hydroquinone, resorcinol, bis-(hydroxyphenyl)-alkanes, bis-
5 (hydroxyphenyl)-ethers, bis-(hydroxyphenyl)-ketones, bis-(hydroxyphenyl)-
sulfoxides, bis-(hydroxyphenyl)-sulfides, bis-(hydroxyphenyl)-sulfones,
and a,a-bis-(hydroxyphenyl)-diisopropylbenzenes, as well as their
nuclear-alkylated compounds. These and further suitable aromatic
dihydroxy compounds are described, for example, in U.S. Patents
3,028,356; 2,999,835; 3,148,172; 2,991,273; 3,271,367; and 21999,846,
all incorporated herein by reference.
Further examples of suitable bisphenols are 2,2-bis-(4-hydroxy-
phenyl)-propane (bisphenol A), 2,4-bis-(4-hydroxyphenyl)-2-methyl-
butane, 1,1-bis-(4-hydroxyphenyl)-cyclohexane, a,a'-bis-(4-hydroxy-
phenyl)-p-diisopropylbenzene, 2,2-bis-(3-methyl-4-hydroxyphenyl)-
propane, 2,2-bis-(3-chloro-4-hydroxyphenyl)-propane, bis-(3,5-dimethyl-4-
hydroxyphenyl)-methane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane,
bis-(3,5-dimethyl-4-hydroxyphenyl)-sulfide, bis-(3,5-dimethyl-4-hydroxy-
phenyl)-sulfoxide, bis-(3,5-dimethyl-4-hydroxyphenyl)-sulfone, dihydroxy-
benzophenone, 2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-cyclohexane, a,a'-
bis-(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropylbenzene and 4,4'-sulfonyl
diphenol.
Examples of particularly preferred aromatic bisphenols are 2,2,-
bis-(4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-
propane and 1,1-bis-(4-hydroxyphenyl)-cyclohexane.
The most preferred bisphenol is 2,2-bis-(4-hydroxyphenyl)-propane
(bisphenol A).
The polycarbonates of the invention may entail in their structure
units derived from one or more of the suitable bisphenols.
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Among the resins suitable in the practice of the invention are
included phenolphthalein-based polycarbonate, copolycarbonates and
terpolycarbonates such as are described in U.S. Patents 3,036,036 and
4,210,741, both incorporated by reference herein.
The polycarbonates of the invention may also be branched by
condensing therein small quantities, e.g., 0.05-2.0 mol % (relative to the
bisphenols) of polyhydroxyl compounds.
Polycarbonates of this type have been described, for example, in
German Offenlegungsschriften 1,570,533; 2,116,974 and 2,113,374;
British Patents 885,442 and 1,079,821 and U.S. Patent 3,544,514. The
following are some examples of polyhydroxyl compounds which may be
used for this purpose: phloroglucinol; 4,6-dimethyl-2,4,6-tri-(4-hydroxy-
phenyl)-heptane; 1,3,5-tri-(4-hydroxyphenyl)-benzene; 1,1,1-tri-(4-hydroxy-
phenyl)-ethane; tri-(4-hydroxyphenyl)-phenylmethane; 2,2-bis-[4,4-(4,4'-
dihydroxydiphenyl)]-cyclohexyl-propane; 2,4-bis-(4-hydroxy-1-isopropy-
lidine)-phenol; 2,6-bis-(2'-dihydroxy-5'-methylbenzyl)-4-methylphenol; 2,4-
dihydroxybenzoic acid; 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-
propane and 1,4-bis-(4,4'-dihydroxytriphenylmethyl)-benzene. Some of
the other polyfunctional compounds are 2,4-dihydroxybenzoic acid,
trimesic acid, cyanuric chloride and 3,3-bis-(4-hydroxyphenyl)2-oxo-2,3-
dihydroindole.
In addition to the polycondensation process mentioned above,
other processes for the preparation of the polycarbonates of the invention
are polycondensation in a homogeneous phase and transesterification.
25 The suitable processes are disclosed in the incorporated herein by
references, U.S. Patents 3,028,365; 2,999,846; 3,153,008; and
2,991 ,273.
The preferred process for the preparation of polycarbonates is the
interfacial polycondensation process.
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Other methods of synthesis in forming the polycarbonates of the
invention such as disclosed in U.S. Patent 3,912,688, incorporated herein
by reference, may be used.
Suitable polycarbonate resins are available in commerce, for
5 instance, Makrolon FCR, Makrolon 2600, Makrolon 2800 and Makrolon
3100, all of which are bisphenol based homopolycarbonate resins
differing in terms of their respective molecular weights and characterized
in that their melt flow indices (MFR) per ASTM D-1238 are about 16.5-
24, 13-16, 7.5-13.0 and 3.5-6.5 9/10 min., respectively. These are
10 products of Miles Inc., of Pittsburgh, Pennsylvania.
A polycarbonate resin suitable in the practice of the invention is
known and its structure and methods of preparation have been disclosed,
for example in U.S. Patents 3,030,331; 3,169,121; 3,395,119; 3,729,447;
4,255,556; 4,260,731; 4,369,303 and 4,714,746 all of which are
15 incorporated by reference herein.
The composition of the invention may include any of the
conventional additives fillers and reinforcing agents. These mineral fillers,
plasticizers, fluidizing agents, stabilizers against UV light, heat, moisture
and the action of oxygen, pigments and flame retardants may be
20 incorporated in the composition in art-recognized amounts by following
conventional procedures.
In a preferred embodiment, the composition further contains (iii)
about 0 to 30 percent of a graft rubber copolymer (iv) about 0 to 30
percent of an aromatic vinyl copolymer and (v) about 0 to 5 percent
25 polytetraflouroethylene (PTFE). In further preferred embodiments, the
composition contains about 3 to 15 percent graft rubber copolymer, 7 to
20 percent aromatic vinyl copolymer, 5 to 30 percent phosphorous
compound and 35 to 85 percent polycarbonate resin.
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The graft rubber copolymer useful in the preferred embodiments of
the invention is an ABS type polymer, the molecules of which contains
two or more polymeric parts of different compositions, namely a rubber
base (substrate) and a graft part (the grafted phase), that are bonded
chemically. These are prepared by polymerizing a suitable monomer, for
instance, butadiene or a conjugated diene, optionally with a comonomer
polymerizable therewith such as styrene, to yield the rubber base. After
the formation of the rubber base at least one grafting monomer, typically
two, are polymerized (grafted phase) in the presence of the rubber base
to obtain the graft rubber copolymer. The graft rubber copolymers which
are preferably prepared by the known emulsion graft polymerization
process are typically obtained by grafting at least one of the following
monomers: chloroprene, butadiene-1,3, isoprene, 1,3-heptadiene, methyl-
1,3-pentadiene, 2,3-dimethylbutadiene, 2-ethyl-1,3-pentadiene, 1,3- and
2,4-hexadiene as well as chloro and bromo-substituted butadienes,
ethylene, propylene, vinyl acetate and C1 ~8 (meth)acrylate esters. Among
the more preferred graft bases, mention may be made of butadiene, and
butadiene/styrene. Other suitable monomers are described in "Methoden
Der Organischen Chemie" (Houben-Weyl), Bd. 14/1, Georg Thieme-
Verlag, Stuttgart 1961, pp.393-406 and in C.B. Bucknall, "Toughened
Plastics", Appl.Science Publishers, London 1977, the disclosures of
which are incorporated herein by reference.
The grafted phase may include styrene and/or acrylonitrile and/or
alkyl (meth)acrylate, vinyl acetate, acrylonitrile and/or styrene.
Preferred graft copolymers are partially crosslinked and have gel
content above 20 percent, preferably above 60 percent, relative to their
weight. These grafts may be obtained by polymerization of 5-90,
preferably 30 to 80, parts by weight (pbw) of a mixture of 50-95 pbw of at
least one member selected from the group consisting of substituted or
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unsubstituted styrene, alpha-methyl styrene and methyl methacrylate and
5 to 50 pbw of at least one member selected from the group consisting of
acrylonitrile methacrylonitrile, methyl methacrylate, maleic anhydride and
maleimide, in the presence of 10-95, preferably 20 to 70, pbw rubber
having a glass transition temperature under -10C, as a graft base.
Especially preferred graft copolymers are ABS grafts.
In the preparation of the graft copolymer, the rubber substrate
conjugated diolefin polymer or copolymer exemplified by a 1,3-butadiene
polymer or copolymer preferably is present at a level of from 15 to 90
percent by weight, and more preferably at from 30 to 70 percent by
weight, and most preferably about 50 percent by weight, of the total ABS
graft polymer. The monomers polymerized in the presence of the
substrate to form the grafted portion, exemplified by styrene and
acrylonitrile, preferably are together present at a combined level of from
about 10 to about 85 percent by weight of the total ABS graft polymer,
more preferably 30 to 70 weight percent thereof and most preferably
about 50 weight percent thereof. It is additionally preferred that the
second group of grafting monomers, exemplified by acrylonitrile ethyl
acrylate and methyl methacrylate, comprise from about 10 percent to
about 40 percent by weight of the grafted portion of the ABS resin while
the monovinylaromatic hydrocarbon monomers, exemplified by styrene,
comprise from about 60 to about 90 percent by weight of the grafted
portion of the ABS resin.
Suitable graft copolymers have been disclosed in U.S. Patents
3,931,356; 3,957,912; 3,991,136; 4,206,293; 4,277,574; 4,559,386;
4,598,124; 5,075,375 and 3,130,177, the disclosures of which are
incorporated herein by reference.
The aromatic vinyl copolymer suitable in the present context is the
polymerization product of at least one, and preferably two monovinyl
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aromatic hydrocarbons. The preferred monovinyl aromatic monomers
utilized are generically described by the formula:
R 1~ /R
R C=C\R
wherein R is selected from the group consisting of hydrogen, alkyl groups
containing from 1 to 5 carbon atoms, cycloalkyl, aryl, alkaryl, aralkyl,
10 alkoxy, aryloxy chloro and bromo. Examples of the monovinyl aromatic
compounds and substituted monovinyl aromatic compounds that may be
used are styrene and other vinyl-substituted aromatic compounds
including alkyl-, cyclo-, aryl-, alkaryl-, alkoxy-, aralkyl-, aryloxy-, and other
substituted vinyl aromatic compounds. Examples of such compounds are
15 3-methylstyrene; 3,5-diethylstyrene and 4-n-propylstyrene, a-methyl-
styrene, a-methylvinyl-toluene, a-chlorostyrene, vinyltoluene, a-bromo-
styrene, chlorophenyl ethylene, dibromophenyl ethylene, tetrachloro-
phenyl ethylene, 1-vinyl-naphthalene, 2-vinylnaphthalene, mixtures
thereof and the like. The preferred monovinyl aromatic hydrocarbon
20 used herein is styrene and/or a-methylstyrene.
The second group of monomers polymerized in the preparation of
the copolymer of the invention conform to
X\ /X
f C Y
X
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wherein X is hydrogen, C1 5 alkyl, chlorine or bromine and Y is selected
from the group consisting of cyano and carbalkoxy groups where the
alkoxy group contains 1 to 12 carbon atoms. Examples include acrylo-
nitrile, substituted acrylonitrile, ethacrylonitrile, methacrylonitrile, a-
5 chloroacrylonitrile, ,B-chloroacrylonitrile, o~-bromoacrylonitrile and
~-bromoacrylonitrile, and/or acrylic acid esters such as methacrylate,
methylmethacrylate, ethylacrylate, butylacrylate, propylacrylate, isopropyl-
acrylate, isobutylacrylate, mixtures thereof and the like. The preferred
acrylic monomer used herein is acrylonitrile and the preferred acrylic acid
10 esters are ethylacrylate and methylmethacrylate. Typically the copolymer
contains about 50 to 95 pbw of the monomer(s) of the first group and
about 5 to 50 pbw of monomer(s) of the second group. The preferred
copolymer is styrene acrylonitrile (SAN) a resin which is well known and
available in commerce.
The tetrafluoroethylene polymers suitable in the present context
are polymers having a fluorine content of about 65 to 76% by weight,
preferably 7 to 76%. Examples are polytetrafluoroethylene, tetrafluoro-
ethylene/hexafluoropropylene copolymers and tetrafluoroethylene
copolymers with small amounts of chlorine-free copolymerizable
20 ethyleneically unsaturated monomers.
These polymers as well as the methods for their preparation are
known - see in this connection U.S. Patents 2,393,697 and 2,534,058;
the disclosures of which are incorporated herein by reference. Suitable
polytetrafluoroethylene are available in commerce, for instance, as
25 Hostaflon TF 2026 from Hoechst.
The preparation of the compositions of the invention follows
conventional procedures which are well known in the art.
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The invention is further illustrated but is not intended to be limited
by the following examples in which all parts and percentages are by
weight unless otherwise specified.
EXAMPLES
Experimental:
Compositions within the scope of the present invention have been
prepared and their properties determined as summarized below. In
preparing these compositions and the comparative compositions the
following materials were used:
POLYCARBONATE: Makrolon 2600 - a homopolycarbonate based on
bisphenol-A, having a melt flow rate of 11 9/10 min. per ASTM
D-1238; (300C, 1.2 kg. Ioad).
COPOLYMER: styrene-acrylonitrile having a weight ratio of S/AN of
about 72/28.
ABS: acrylonitrile-butadiene-styrene graft polymer, having a
polybutadiene content of about 50 weight and a weight ratio of
styrene/acrylonitrile of 72/28.
PTFE: polytetrafluoroethylene was added to the composition as a
concentrate of 10% PTFE in ABS. The ABS used in the
preparation of the concentrate was characterized in that it
contained 55% by weight polybutadiene and the remainder (45%)
contained SAN in a weight ratio of styrene/acrylonitrile of 72/28.
The amount of ABS noted in the table includes the ABS derived
from the concentrate.
The phosphate compound in composition A: resorcinol diphenyl
phosphate conforming to
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O O
<~0 10~0 ~jl 0~
n
in composition C: neopentyl glycol bis(diphenyl phosphate) conforming to
O CIH3 1
PHO--IP OCH2 C CH2---- IP OPH
OPH ~ CH3 OPH n n = about 1
in composition B: bisphenol A(diphenylphosphate) conforming to
O - O-
PHO--P ~ ¦ C~}O P--OPH
OPH OPH n = about 1
in composition D: resorcinol dixylylphosphate conforming to
(R)2--P~O --P ) n (~) 2
n = about 1
wherein
C H3
R =~-CH3
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The amounts of the components were adjusted so as to obtain a
substantially identical phosphorous content in the compositions.
Table 1
A B C D
I ngredient
Polycarbonate 68.4 66.9 66.1 66.9
copolymer 10.2 10.0 9.9 10.0
ABS 7.7 7.5 7.4 7.5
phosphate 10.2 12.3 13.2 12.3
PTFE 3.6 3.4 3.4 3.4
approxi" IdL~ P%
in formulation 1.10 1.10 1.18 1.10
MeK Flow Rate'
(g/10 min) 20.8 40.5 39.7 32.7
Spiral Flow2, inches 25.25 32 32 29
Tensile Strength,
Yield (kpsi) 8.7 9.0 8.8 9-4
Elongabon atYield (%) 3.0 3.2 2.4 2.4
Tensile Strength,
@Break (kpsi) 8.6 6.9 7.6 7.5
Elongdlion at Break (%) 118.0 63.0 122.0 95.8
Flexural Strength (kpsi)15.7 15.7 15.1 16.1
Flexural Modulus (psi x 105) 4.2 4.2 4.2 4.3
Vicat, VST B/120C 97.6 92.3 84.7 94.3
Notched Izod Impact
.125 in. 73F (ft~lbs) 13.7 12.2 13.1 10.2
Instrumented Impact 23C,
125 mil, Total Energy (ft~lbs) 41.8 39.4 38.0 39 7
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TABLE 1 (Cont.)
A B C D
Fla"""abilil~r UL 94 5V
125 mil 5V 5V Fail Fail
Melt Stability @ 5min636 345 409 382
35min 654 364 345 318
~ 65min 654 364 345 318
Melt Viscosity (Pa~s) at:
8.5 1 218 582 945 709
17.0 1 000 518 700 682
42.6 764 400 491 436
85.1 636 345 409 382
170.2 573 327 373 350
425.5 407 244 273 256
1 5 851.0 298 196 205 204
1702 209 147 149 152
' @250C and 50009 load
2 100 mil @ 490F
The results demonstrate the higher melt flow rate and improved
20 spiral flow, which characterize compositions B and C which represent the
invention.
Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood that such
detail is solely for that purpose and that variations can be made therein
25 by those skilled in the art without departing from the spirit and scope of
the invention except as it may be limited by the claims.
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