Note: Descriptions are shown in the official language in which they were submitted.
8 CH 2335
This invention relates to thermoplastic molding
compositi.ons which, when ultrasonically bonded or welded in
the molded state to acrylic or polycarbonate polymers, possess
improved bond strength in the ultrasonically formed bond. More
particularly the present compositions comprise, in admixture,
a polyphenylene ether resin, a styrene resin, preferably a
rubber modi~ied high impact polystyrene, a polymeric material
which is polar in rela-tion to the polystyrene component and,
optionally, an A-B-A block copolymer. In order to confer the
desired polyphenylene ether/polystyrene to acrylic bond
strengths, the polar polymeric material should be present in
at least 40 parts by weight per 100 parts by weight of said ~ :
polyphenylene ether resin and said styrene resin.
I The polyphenylene ether resins are known and
described in numerous publications, including Hay, U.S.3,306,874
dated February 28, 1967 and 3,306,875 dated February 28; 1967
: and stamatoff, U.S. 3,257,357 dated June 21, 1966 and
3,257,358 dated June 21, 1966. In Cizek, U.S. 3,383,435
; dated ~ay 14, 1968 , it is disclosed that polyphenylene ethers
and polystyrene resins, including many modified polystyrenes,
: are combinable in all proportions to provide compositions
having many properties impro~ed over those of either the
polyphenylene ether resin or the polystyrene resin alone.
Compositions of polyphenylene ether and polystyrene are useful
for many commercial applications and because they are
thermoplastic, they can be shaped into various articles by
compression molding, extrusion, or the like. The shaped
articles can then, in turn, be joined with other parts in
plastics welding operations.
Ultrasonic methods o~ assembly provide an especially
use~ul means for welding or bonding plastics to plastics. In
general, ultrasonic vibrations above the audible range are used
*~
~ 3.~ 8 CH ~335
to generate localized heat by vibrating one plastic surface
against the other. Sufficient frictional heat is released,
usually within a fraction of a second, to cause most
thermoplastic materials to melt~ flow and fuse. Ultrasonic
methods of assembly are cleaner, faster, and more economical
than conventional bonding methods, and they avoid the need or
applied heat, solvents, adhesives, curing times, and the like.
The ultrasonic bonding o~ thermoplastic materials is
described in further detail in the "Encyclopedia o Polymer
lQ Science and Technolo~y", ~olume 1~, John Wiley & Sons, Inc.,
1971, pages 116-124.
Although ultrasonic bonding provides numerous advan~
tagesl as mentioned above, when molded parts made of polyphenylene
ether/polystyrene compositions have heretofore been joined or
welded to acrylic or to polvcarbonate polymers using ultrasonic
techni~ues, it has been possible to form only relatively weak
bonds. For most practical applications, a bond strength of about -
3QO lbs. or greater is required. ~owever, when prior art poly~
phenylene ether/polystyrene compositions are ultrasonically -~
2Q bonded to acrylic or to polycarbonate polymers, bond strengths
of far less than 300 lbs. are typically obtained.
It has now been surprisingly discovexed that if at
least a portion of the polystyrene component in polyphenylene
; ether/polystyrene compositions is replaced by a component which
is polar in relation to the polystyrene compon~nt, the resulting
thermoplastic compositions can be ultrasonically bonded to
acrylic or to polycarbonate polymers with unexpectedly improved
bond strengths in the ultrasonically formed bond.
Accordingly, the present invention, in its broadest
aspects, provides thermoplastic molding compositions which are
ultrasonically bondable or weldable in the molded state, i.e.,
after being compression molded, ~xtruded, or the li3~e, to
acrylic or to polycarbonate polymers with improved bond
8 C~l 2335
strength in the ultrasonically formed bond, the compositions
comprising an admixture of:
(a) a polyphenylene ether resin;
(b) a styrene resin; and
(c~ a polymeric material which is
polar in relation to styrene resin (b)
The polyphenylene ether resins of this invention
are described in detail in the above-mentibned Hay and Stamatoff
~i patents. In general, the polyphenylene ether resin (a~ is a
self-condensation product of monohydric, monocyclic phenols
which can be produced, for example, by reacting the phenols
with oxygen in the presence of complex copper catalysts. The
molecular weight can be controlled by reaction time, longer
times providing a higher average number of repeating units.
A preferred family of polyphenylene ethers will
have repeating structural units of the formula:
20 ~ Q ~n ~I~
wherein the oxygen ether atom of one unit is connected to the
benzene nucleus of the next adjoining unit, n is a positive
integer and is at least 50, and each Q is a monovalent sub-
stituent selected from the group consisting of hydro~en, halo- -
gen, hydrocarbon radlcals;free of a tertiary alpha-carbon atom,
halohydrocarbon radicals having at least -~wo carbon atoms
between the halogen atom and the phenyl nucleus, hydrocarbonoxy
xadicals and halohydrocarbonoxy radicals having at least t~o
carbon atoms between the halogen atom and the phenyl nucleus.
~ For purposes of the present lnvention an especially
.~ ,
~3~3 ~ 8 CH 2335
preferred family of polyphenylene ethers include those having
alkyl substitution in the two positions ortho to the oxygen
e-ther atom, i.e., those of the above formula wherein each Q
is alkyl, most preferably having from 1 to 4 carbon atoms.
Examples include poly (2,6-dimethyl-1,4-phenylene)ether, poly
(2,6-diethyl-1,4-phenylene)ether, poly(2-methyl-6-ethyl-1,4-
phenylene)ether, poly(2 methyl-6-propyl-1, 4-phenylene)ether,
poly(2,6-dipropyl-1,4-phenylene)ether, and poly(2-ethyl-6-
propyl-1,4-phenylene~ether. Especially preferred is poly ;
(2,6-dimethyl-1,4-phenylene)ether.
The styrene resin (b), in general, will be selected
from those having at least 25% by weight of the polymer units -~
- derived from a vinyl aromatic monomer, e.g., one having the
..
formula: --
RC=jH
(II)
wherein R is hydrogen, (lower) alkyl, e.g., of from 1 to 4
carbon atoms or halogen; Z is hydrogen, vinyl, halogen or (lower)
alkyl; and p is 0 or a whole number of from 1 to 5. Illustrative
polystyrene resins include homopolymers of polystyrene, poly-
chlorostyrene, poly-2 methylstyrene, and the like; styrene-
containing copolymers, such as styrene-acrylonitrile copolymers,
copolymers of ethylvinylbenzene and divinylbenzene, styrene-
acrylonitrile-a-methylstyrene terpolymers, and the like.
Preferred polystyrene resins of this class are
i~
rubber-modified, high impact styrene resins, i.e., polystyrene
which has been modified with natural or synthetic ma~erials
~whic~ a~e el~s~tomers~ at room tem~erature~ e g~ 20 to 25 C.
The term "rubber" therefore includes polybutadiene, polyiso-
- 4 -
. ~ .
~ 3 !~ 8 CH 2335
prene, rubbery copolymers of dienes with other comonomers, such
as styrene, acrylonitrile, acrylic esters and the li~e, including
block sopolymers of the A-B-A and A-B type wherein A is a vinyl
aromatic, such as styrene, and B is a diene such as butadiene,
as well as EPDM rubber and the like. Most preferably, the
polystyrene is modified with a butadiene rubber.
Component (c) is a polymeric ma~terial which is
characteristically polar in relation to polystyrene resin (b).
The presence of polar component (c) is essential for the achieve-
ment of improved bond strengths in the ultrasonic bonding ofpolyphenylene ether/ polystyrene blends with acrylics or polycarbon-
ates. The nature of polar component (c) can vary, provided the
requisite property of polariky relative to polystyrene component
(b) is always present. Especially preerred polar materials in-
clude copolymers of a vinyl aromatic compound ànd an ~ un-
saturated cyclic anhydride, e.g., styrene-maleic anhydride co-
polymers; copolymers of a vinyl aromatic compound and an acrylic
ester, e.g., styrene-methyl methacrylate copolymers; and terpoly-
~ers of a vinyl aromatic compound, an acrylic ester and a diene,
e.g., styrene-methylmethacrylate-butadiene.
As is described in Cizek, U.S. 3,383,435 dated
May 14, 1968, polyphenylene ethers and polystyrene resins are
combinable with each other in all proportions. Thus, the
present compositions can comprise from 1 to 99% by weight `~
polyphenylene ether resin and from 99 to 1% by weight
polystyrene resin, on a rubber-free basis, and these are
included within the scope o~ the invention.
Polar component (c) is present in amounts of at
leas-t 40 and up to about 150 parts by weight, based on 100 parts
by weight of components (a) and (b). Such amounts are necessary
in order to achieye u~able bon~ stren~ths in ~ltrasonically ~orm~
ed bonds with acrylic polymers~ ~mounts o~ polar compone~t ~c)
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of ~rom about 40 to 120 parts by weight per 100 parts by weight
of (a~ and (b) are especially preferred. Higher amounts may be
employed but impact strength may be adversely afected. ;~
In general, if more cyclic anhydride or acrylate is
present in the copolymer or terpolymer component (c), less of
component (c) need be combined with (a) and (b) to produce the
desired degree of bondability.
Other ingredients, such ~s plasticizexs, pigments,
flame retardants, reinforcing agents, stabilizers, and the like,
can be added for their conventionally employed purposes. In such
cases, all concentrations and ratios of the resinous ingredients
disclosed herein, and the like, will be adjusted accordingly to `~
. .
reflect the presence of such additives.
The method of forming the compositions of the
invention is not critical and ~arious conventional means can be
employed. The preferred method is one in which the ingredients
are admixed to form a preblend, the preblend is processed through
an extruder and the extrudate is molded to any desired shape
such as by extrusion, hot molding or the like.
The invention is further illustrated by the
following examples, which are not to be construed as limiting.
Unless otherwise indicated, all compositions are prepared by
blending, then passing the blend through a variable pitch,
twin screw extruder with extrusion temperature maintained
between 500 and 600F. The emerging strands are cooled, chopped
into pellets and molded into test bars using a Newbury
injection molding machine. The test bars are tested ~ox
physical properties according to ASTM test methods. All parts
o the compositions shown in the examples are by welght.
3a Examples 1-7
The following composi-tions were prepared, molded
into test bars and tested for physical properties.
~34~3 L
8 CH 2335
(Parts by Examples
Components We'i~ht~ 1 2* 3 4* 5 6 7
Polyphenylene ether
resina 25 25 40 35 30 20 30
Rubber modified,
high-impact poly-
styrene resin -- 65 -- 40 -- -- --
Styrene-butadiene-
styrene resinC 15 -- 20 -- 20 20 20
Styrene-methyl-
methacrylate co-
polymer (60:40)d 60 -- -- -- -- -- --
Styrene-maleic
anhydride co-
polymere -- -- 40 25 50 60 50
Triphenyl phosphate -- -- 4 -- -- -- 4
Acryflic copoly-
mer -- 10 -- -- -- -- --
* Control Experiments
a Poly(2,6-dimethyl-1,4-phenylene)ether, intrinsic
viscosity about 0.45 dl/g in CHC13 at 30C., PPO,
General Electric Co.,
b Foster Grant Co., Leominster, Mass., FG 834
c Shell Chemical Co., Houston, Texas, Kraton 1101
d The Richardson Co., Des Plaines, Ill., NAS 8L '
e ARCO Polymers, Inc., Pittsburgh, Pa., Dylark 232
f Rohm & Haas Co., Philadelphia, Pa., Acryloid KM 611
Properties 1 2 3 4 5 6
Heat DOeflection
temp.( F.) 203 220 237 247 245 234 225
Izod impact (in.
lbs~/in.n.) 1.6 4.0 4.6 2.0 2.5 2.6 2.7
M.V. (poise~ 2050 1950 1900 1400 1700
Test pieces molded from the compositions of
Examples 1-7 were ultrasonically welded to molded ~est pieces of
a polyphenylene ether resin high impact polystyrene resin and
test pieces of an acrylic resin, respectively. The welded
pieces were tested for bond strengths at failure under tensile
type loading conditions, using an Instron testing machine. The
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8 CH 2335
bond strengths at break, in units of pounds, are shown in
Table I (for comparison purposes, an acrylic-to-acrylic
ultrasonic bond strength is 425 lbs.):
TABLE 1
ULTRASONICALLY WELDED BOND STRENGTHS
Bonded to polyphenylene
ether/polystyrene Bonded to Acrylic
Example No~ ~Break Force in lbs.) ~Break Force ln lbs.)
1 550 425
2* 625 200 -
3 825 300
4* 425 200
825 400
6 475 375
7 900 425
* Control Experiments
A bond strength of at least about 300 pounds is
generally accepted;to be necessary for practical applications.
Compositions 1-3 and 5-7, according to this invention, equal ;
or exceed this value. If less than 40 parts of (c) per 100
parts of ~a) and (b~ are used, Control Example 4 (36 parts),
it is seen that the bond strength falls below the minimum.
EXAMPLES~8 - 10
The general procedure of Examples 1-7 is repeated,
substituting a styrene-maleic anyydride-butadiene rubber for
component (c). The formulations used and the physical propexties
obtained are set forth as folIows:
EXAMPLE 8 9 10
Compositions (parts by weight)
poly(2,6-dimethyl-1,4-phenylene
0 ether (as is Examples 1-7) 25 25 35
Rubber modified high impact
polystyrene resin (as in
Examples 1-7) 25 25 20
-- 8
~3~3 ~ 8 CH 2335
Styrene-butadiene-styrene
resin (as in Examples 1-7) 5 3
Styrene-maleic anhydride-
butadiene terpolymer resin
(80:10-10)a 50 50 45
Properties
-
Heat distortion temperature, F. 236 235 246
Izod impact strength, ft.lbs./
in Notch 2.8 1.9 3.0
Melt viscosity, poise 1,600 1,400 1,600
.
a ARCO Polymers, Inc., Pittsburgh, Pa., Dylark 240
The bond strengths at break, in units of pounds,
are shown in Table 1 for ultrasonic bonds to acrylic and to
poly-carbonate (Lexan 103) substrates:
TABLE 2
ULTRASONICALLY WELDED BOND STRENGTHS '
Bonded to Acrylic Bonded to Polycarbonate
Example No. (Break Forc_ in Pounds) (Break Force in Pounds)
8 400 500
9 425 (not deter~ined)
400 600
It is seen that highly efficient, ultrasonically
bondable compositions according to this invention are obtained.
Obviously, other variations are possible in the
light of the above description. It is to be understood, therefore r
that modifications may be made in the compositions disclosed
herein which are within the full intended scope of the present
invention as defined in the appended claims.
