Note: Descriptions are shown in the official language in which they were submitted.
13~33 Mo-2879
PC-186
POLYCARBONATE MOLDING COMPOSITIONS
Field of the Invention
.
The invention is directed to polycarbonate
molding compositions and more particularly to
composi~ions suitable for the preparation of molded
articles having a metal coating electrolessly deposited
thereon.
Summary of the Invention
A molding composition comprising a
polycarbonate resin and an acrylate-based plating
modifier was found to be suitable for preparing metal
coated articles where the metal coating is deposited by
an electroless process. In a preferred embodiment of the
invention the molding composition further comprise a
flame-retarding agent.
Back~round of the Invention
Electroless plating of articles molded from
polycarbonate resins are used in the manufacture of EMI
shielded articles. Processes for electroless plating
have been disclosed in U.S. Patent 4,125,649 and in the
Encyclopedia of Polymer Science and Technology, Vol. 8
among others.
Polycarbonate molding compositions containing
acrylate rubber have been reported in U.S. Pa~ents
4,299,928 and 4,378,449 In these patents, the addition
of 1 to 20 percent of acrylate rubber percent is said to
result in improved impact performance.
Flame retarding agents for polycarbonates are
known. Such agents have been disclosed in the patent
literature and in the manuscript The Chemistry & Uses of
Fire Retardants, John W. Lyons, Wiley Interscience,
1970.
'
Mo-2879
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DETAILED DESCRIPTION OF THE INVENTION
The Polycarbonate Resin
The polycarbonate resins useful in the practice of
the invention are homopolycarbonates, copolycarbonates
and terpolycarbonates or mixtures thereof. The
polyca~bonates generally have a molecular weight of
10,000-200,000 (weight average molecular weight),
preferably 20,000-80,000 and their melt flow rate, per
ASTM D-1238 at 300~C, is about 1 to about 24 gm/10 min.,
preferably about 2-15 gm/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 Offenlegungs-
schriften 2,063,050; 2,063,052; 1,570,703; 2,211,956;
2,211,957 and 2,248,817; French Patent 1,561,51~; and the
monograph H. Schnell, "Chemistry and Physics of Poly-
carbonates", Interscience Publishers, New York, 1964.
In the present context, dihydroxy compounds suitable
for the preparation of the polycarbonates of the
invention conform to the structural formulae (1) or (2)
~ (A) ~ ~ OH
25 HO ~ L (Z)d ~ e
HO ~H
(Z)d ~ (2)
(Z)f (Z)f
wherein
A denotes an alkylene group with 1 to 8 carbon atoms, an
alkylidene group with 2 to 8 carbon atoms, a cyclo-
alkylene group with 5 to 15 carbon atoms, a cyclo-
Mo2879 - 2 -
'A
i,,,.,,,,,",,,",, .. ~ :
.
13 ~ 3
alkylidene group with 5 to 15 carbon atoms, a carbonyl
group, an oxygen atom, a sulfur atom, -S0- or S02- or a
radical conforming to
IH3
S ~H3 ~ CH3 , ~ ,
- C ~ C _ or - C ~ ~ CH3
CH3 CH3 CH3
e and g both denote the number 0 to 1,
Z denotes F, Cl, Br or Cl-C4-al~yl and if several ~
radicals are substituents in one aryl radical, they may
be identical or different;
d denotes o or an integer of from l to 4; and
f denotes o or an integer of from 1 to 3.
Among the useful bisphenols in the practice of the
invention are hydroquinone, resorGinol, bis-(hydroxy-
phenyl)-alkanes, bis-(hydroxyphenyl)-ethers, bi 5-
(hydroxyphenyl)-ketones, bis~(hydroxyphenyl)-sulfoxides,
bis-(hydroxyphenyl)-sulfides, bis-(hydroxyphenyl)-
sulfones~ and a,~'-bis-(hydroxyphenyl)-diisopropyl-
benzenes, 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
2,999,846. Further examples of suitable bisphenols are
2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A), 2,4-bis-
(4-hydroxyphenyl)-2-methyl-butane, 1,1-bis-(4-hydroxy-
phenyl)-cyclohexane, a,a'-bis-~4-hydroxyphenyl)-p-diiso-
propylbenzene, 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, hydroxybenzophenone, 2,4-bis-(3,5-dimethyl-4-
hydroxyphenyl)-cyclohexane, a,a'-bis-(3,5-dimethyl-4-
Mo2879 -3-
: .
~ 3
hydroxyphenyl)-p-diisopropylbenzene and 4,4'-sulfonyl
diphenyl .
Examples of particularly preferred aromatic
bisphenols are 2,2-bis-(4-hydroxyphenyl)-propane,
2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane and
l,1-bis-(4-hydroxyphenyl)-cyclohexane.
The most preferred bisphenol is 2,2-bis-(4-hydroxy-
phenyl)-propane (bisphenol A).
The polycarbonates of the in~ention may entail in
their structure units derived from one or more of the
suitable bisphenols.
Among the resins suitable in tke 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.
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 Offenlegungs-
schriften 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-hydroxyphenyl)-heptane; 1,3,5-tri-
(4-hydroxyphenyl)-benzene: 1,1,1-tri-(4-hydroxyphenyl)-
ethane; tri-(4-hydroxyphenyl)-phenylmethane; 2,2-bis-
~4l4-(4l4~-dihydroxydiphenyl)-cyclohexyl]-propane; 2,4-
bis-(4-hydroxy-1-isopropylidine)-phenol; 2,6-bis-(2'-
dihydroxy-5'-methylbenzyl)-4-methylphenol; 2,4 di-
hydroxy-benzoic acid; 2-(4-hydroxyphenyl)-2-(2,4-di-
hydroxyphenyl)-propane and 1,4-bis-(4,4'-dihydroxytri-
phenylmethyl~-benzene. Some of the other polyfunctional
compounds are 2,4-dihydroxybenzoic acid, trimesic acid,
cyanuric chloride and 3,3-bis-(4-hydroxyphenyl)-2-
Mo2879 -4-
~ 3 ~
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. The
suitable processes are disclosed in 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.
Other methods of synthesis in forming the
polycarbonates of the invention such as disclosed in U.S.
Patent 3,912,688 may be used.
Suitable polycarbonate resins are available in
commerce, for instance, under the tradenames Merlon FCR,
Merlon M-39, Merlon M-40 and Merlon M-50, all of which
are bisphenol A based homopolycarbonate resins differing
in terms of their respective molecular weights and
characterized in that their melt indices per ASTM D-1238
2G are about 16.5-24, 13-16, 7.5-13.0 and 3.5-6.5 gm/10
min., respectively. These are products of Mobay
Corporation of Pittsburgh, Pennsylvania.
Flame retardant agents for polycarbonate resins are
known in the art. These agents have been widely reported
in the patent literature and include halogenated
compounds, especially brominated compounds and most
particularly aromatic brominated compounds, sulfonate
salts of alkali metals or alkaline earth metals and
complex ion metal salts, such as sodium aluminum
fluoride, and phosphorus compounds. The relevant
literature includes U.S. Patent 3,146,254, which
discloses tri-bisphenol A ester of phosphoric acid, U.S.
Patent 3,823,175 relating to halogenated neopentyl
chloroformates, U.S. Patent 4,195,156 entailing
disulfonic acid salts and U.S. Patent 4,269,762 relating
to tetrahydrocarbylborate salts. Also relevant are U.S.
Mo2879 -5-
A
~3~3c3
Patents 3,027,349 (phosphate polymers), 3,475,372 (metal
salts of mercaptobenzotriazoles), 3,509,090 (halogenated
organosilicones), 3,535,300 (organo metal salts),
3,557,053 (tris-halophenyl phosphates), 3,597,390
(tris-halophenyl phosphites), 3,775,367 (perfluorosul-
fonate salts), 3,836,490 (alkali metal salts), 3,875,107
~alkali metal salts), 4,017,457 (ferrocene), 4,098,754
(alkali metal organic salts), 4,100,130 (sulfur),
4,174,359 (oligomeric tetrabromo polycarbonate and
sulfonate salts), 4,223,100 (alkali metal salts, PTFE and
an aromatically bound bromine) as well as U.S. Patents
3,382,207 (decabromodiphenyl carbonate~, 3,647,747
(barium carbonate), 3,651,174 (BaCO3, organosiloxane and
PTFE), 3,796,772 (titanates), 3,867,336 (an arloxy
substituted polyhalogenated aromatic compound; U.S.
Patents 3,931,100, 3,940,366, 3,951,910, 3,953,396,
3,978,024, 4,001,175, 4,007,155, 4,032,506, 4,033,930,
4,039,509, 4,064,101, 4,067,846, 4,073,768, 4,075,164,
4,093,590, 4,093,589, 4,104,245, 4,104,246, 4,115,354,
4,153,595, 4,201,832, 4,263,201, 4,268,429, 3,909,490,
3,917,559, 3,919,167 (sulfonic acid salts), 3,933,734
(sulfonates), 3,948,851, 4,092,291 (sulfone-sulfonic
salts), 3,953,399 (carboxylic acid esters), 3,971,756
(alkali metal salts and siloxanes), 4,028,297 (salts of
inorganic sulfur oxyacids), 4,066,618 (metal salts of
halogenated nonaromatic carboxylic acid), 4,069,201,
4,111,977 (unsubstituted or halogenated oxycarbon acids),
4,104,253, 4,113,695 (halogenated organic metal salts),
4,209,427 (formaldehydes), 4,220,583 (partially
fluorinated olefins), 4,235,978 (organopolysiloxanes),
4,241,434 (alkali or alkaline earth metal salts) and
4,254,252 (cyclic performates). Preferably the flame
retarding agents are sulfonate salts and halogenated
aromatic compounds.
The plating modifier suitable in the composition of
the invention is an acrylic rubber graft copolymer. Such
Mo2879 -6-
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graft copolymers have been described in interpolymeric
composites in U.S. Patents 4,096,202 and 3,808,180 and as
graft copolymers in U.S. Patent 4,022,748.
Acrylic rubber interpolymer composites are
compositions comprising about 25 to 95 percent by weight
of a first elastomeric phase and about 75 to 5 percent by
weight of a second, rigid, theromplastic phase. The
first phase is polymerized from about 75 to 99.8 percent
by weight C1 to C6 acrylate resulting in an acrylic
rubber core having a glass transition temperature below
about 10C which is cross-linked with 0.1 to 5 percent by
weight of a cross-linking monomer and to which is added
0.1 to 5 percent by weight of a graft-linking monomer.
The preferred alkyl acrylate is butyl acrylate. The
cross-linking monomer is a polyethylenically unsaturated
monomer having a plurality of addition polymerizable
reactive groups all of which polymerize at substantially
the same rate of reaction. Suitable cross-linking
monomers include polyacrylic and polymethacrylic esters
of polyols such as butylene diacrylate and dimeth-
acrylate, trimethylol propane trimethylacrylate and thelike, di- and trivinyl benzene, vinyl acrylate and
methacrylate, and the like. The preferred cross-
linking monomer is butylene diacrylate. The
graft-linking monomer is a polyethylenically
unsaturated monomer having a plurality of addition
polymerizable reactive groups, at least one of which
polymerizing at a substantially different rate of
polymerization from at least one other of said reactive
groups. The function of the qraft-linking monomer is to
provide a residual level of unsaturation in the
elastomeric phase, particularly in the later stages of
Mo2879 7
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polymerization and consequently at or near the surface
of the elastomer particles. The preferred graft-linkin~
monomers are alkyl methacrylate and dialkylmaleate.
The final stage monomer system can be comprised
of Cl to C16 methacrylate, styrene, acrylonitrile, alkyl
acrylates, alkyl methacrylate, dialkyl methacrylate, and
the like. Preferably, the final stage monomer system is
at least 50 weight percent Cl to C4 alkyl methacrylate.
A certain acrylic rubber interpolymer composite
characterized in that acrylic rubber core is comprised
of n-butyl acrylate and in that its cross-linking agent
is 1,3-butylene diacrylate and in which the
graft-linking agent is diallyl maleate and the second
phase monomeric system of which is methylmethacrylate is
available under the tradename Acryloid KM 330 from Rohm
& Haas. Additional suitable acrylate based plating
modifiers are available from Rohm & Haas under the trade
names Acryloid KM 2330, 3330 and 2301 (also known as ES
8301SXP).
Other suitable graft copolymers have rubber
; elastic properties and a glass transition temperature
below -20C. Their preparation entails a prepolymer
made from at least 10% of a Cl-C15 acrylate and from
0.1~ to about 10% of a graft linking monomer having 2
olefinic double bonds which are not conjugated. The
prepolymer is grafted with 10-85 parts by weight,
preferably 20 to 75 parts by weight of styrene and/or
methacrylates and/or methacrylic or acrylic acid. The
parts by weight are in relation to 100 parts of
prepolymer.
In the practice of the invention, a
thermoplastic molding composition is prepared by
blending a polycarbonate resin with up to about 1
percent, preferably 0.30 to about 0.95 percent, most
prefelrably 0.40 to about 0.85 percent of a plating
modifier, said percents being relative to the total
weight of the resin and modifier.
Mo-2879 -8-
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13.~ 3 ~ ~
In addition the composition contains a flame
retarding agent in an amount suf f icient to render the
composition a flammability rating of V-O, 1/8" in
accordance with UL-94.
The compositions of the invention may further
contain auxiliary additives such as pigments,
stabilizers, release agents, fillers and reinforcing
agents all of which are conventional and are known in the
art.
The invention is illustrated below but is not
intended to be limited by the examples in which all parts
and percentages are by weight unless otherwise specified.
EXAMPLES
EXAMPLE 1
Compositions within the scope of the invention
were prepared and test specimens molded therefrom. The
preparation and molding steps followed conventional
procedures and used known equipment. In the examples,
the resin was Merlon M-39 polycarbonate and Acryloid KM
330 interpolymer composite was used as the plating
modifier in the indicated compositions. A flame
retarding agent, potassium perfluorobutane sulfonate, was
included in compositions 1-1 and 1-2. Pigments, and in
compositions 1-1 and 1-2 also a mold release agent,
neither having criticality in the present context were
also included.
The molded specimens were coated with a thin
layer of copper deposited by an electroless process. The
table below summarizes the results of the evaluation of
the compositions.
Mb-2879 ~9~
~B
131~
Compositions 1~ 2 1-3
Polycarbonate, % 98.4 97.6 95.2
Flame retarding agent, % 0.1 0.1
Plating modifier - 0.75 4.5
Melt index, gm/10 min. 16.5 15.1 10-11
Impact strength, Notched Izod,
ft. lb/in 1/8" 15.2 15.1 15.5
1/4"1.9 1.9 12.5
Critical thickness, mils 145 145 400
Flammability rating,
UL-94, 1/8" V-0 V-0 HB
after 7 days aging(l) V-0 V-0
Platability (2)
Pre etch 2.125 min. 4/B 5/5 5/5
3.0 min. 2/B 5/5 5/5
(1) aging conditions per UL-94 V-0
(2) determined as cross-hatch adhesion per ASTM
D-3359-78. The numbers indicate a rating on a
scale of 1-5 (corresponding to worst-best); B
denotes blisters. The values are given as
determined on ~7as is" specimens and on aged
specimens (as-is/aged).
EXAMPLE 2
Further compositions in accordance with the
invention were prepared and their properties determined
a~ shown below. In this series the resin was Merlon FCR
polycarbonate which is a homopolycarbonate based on
bisphenol A having a melt flow index of about 22.5 gm/10
min. The compositions also contained the indicated
amount of a plating modifier (Acryloid KM 330
interpolymeric composite) and about 0.1~ of a flame
Mo-2879 -10-
13~
retarding agent (potassium perfluorobutane sulfonate).
Molded specimens were prepared using conventional means
and procedures and the specimens coated with a thin
~ayer of copper by an electroless process. The peel
s~rength, indicating the degree of adhesion of the
coating to the molded part was determined as shown
below.
CompositionPlating Peel
modifier, % strength, psi
2-1 0.0 2.8
2-2 0.68 4.8
2-3 0.75 5.0
2-4 0.83 5.0
A similar evaluation based on compositions where the
polycarbonate resin had a melt flow index of
14.0 gm/10 min. yielded the following results.
CompositionPlating, Peel
modifier, % stren~h~ psi
2-5 0.0 5.3
2-6 0.3 3.2
2-7 0.45 7.2
2-8 0.60 7.8
Mo-2879 -11-
.
1 3 ~
EXAMPLE 3
In yet another series of experiments plaques
were molded from polycarbonate compositions containing
O.75~ of Acryloid KM 330 interpolymer composite and 0.1%
of potassium perfluorobutane sulfonate. The specimens
were coated with a thin layer of ~opper by an
electroless process. The coated plates were then dried
and oven-aged at 85C and the formation of blisters
resulting during the aging process was monitored. A
comparison between the performance of these compositions
and control compositions which contained no plating
modi~ier i6 presented below:
Composition Plating Appearance After thermal agin~
As is after 12 after 2
days days
3-1 0.0 NB NB B
3-2 0.0 NB NB B
3-3 0.75 NB NB NB
3-4 0.75 NB NB NB
(1) Compositions 3-1 and 3-3 are based on Merlon M-39
and compositions 3-2 and 3-4 are based on Merlon-FCR
(2) NB - no blisters; B-blisters
Although the invention has been described in
detail in the foregoing fGr the purpose of illustration,
it is to be understood that such detail is solely for
that purpose and that variations can be made therein 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.
Mo-2879 -12-
