Note: Descriptions are shown in the official language in which they were submitted.
- 1 - 8CN 81~7
THERMOPLASTIC COMPOSITION OF POLYPHENYLENE ETHER,
ETHYLENE-MET~CRYLIC ACID COPOLYMER, AND
STYRENE-GLYCIDYL METHACRYLATE COPOLYMER
-
Background of the Invention
1. Field of the I vention
This invention relates to compositions of a
polyphenylene ether resin, high impact polystyrene,
poly(ethylene-co-methacrylic acid), poly(styrene-co-
glycidyl methacrylate), and optionally a styrene-
ethylene/butylene-styrene block copolymer and polyethylene,
; which have improved properties.
2. Description of the Prior Art
-
The polyphenylene ethers are a family of
thermop]astic engineering resins known to be useful
with polystyrene resins to form compositions that can
be extruded and molded into articles of various shapes
and sizes. The resulting products range from parts and
housings for household appliances to components for
automobiles.
Efforts have been made to combine the
polyphenylene ether resin with still other polymers,
such as polyethylene, to achieve compositions having
property profiles useful for certain specialty applications.
Compositions of this type have been described in the
patent literature, for example, in U.S. Patents
4,166,055, lssued August 28, 1979 to Lee Jr. and
~,239,673, issued December 16, 1980 to Lee Jr.
In general, such compositions are blends of a
~25;~
- 2 ~ 8CN 81g7
polyphenylene ether resin, a high impact polystyrene,
an elastomeric block copolymer of, e.g., styrene and
butadiene, and a polyolefin such as polyethylene.
Articles molded from them exhibit better resistance to
chemical solvents than conventional blends of poly-
phenylene ether and high impact polystyrene, which is
important for many commercial applications. However,
shortcomings include low tensile strengths and a
tendency to undergo delamination in the molded part
near the gate.
Summary of the Invention
It is an object of this invention to provide
thermoplastic extrusion and molding polyphenylene ether
compositions which show good chemical solvent resistance
in combination with improved tensile strength and
resistance to undergoing delamination.
It is a further object of this invention to
provide articles molded from such compositions.
These objects are successfully achieved
with the prac-tice of the present invention, which is
summarized below.
In essence, it has now been discovered that
compositions of polyphenylene ether resin and poly-
ethylene can be modified to replace at least part of
the polyethylene with a combination of major amount of
an ethylene-methacrylic acid copolymer and a minor
amount of a styrene-glycidyl methacrylate copolymer,
and to achieve a more homogeneous blend. Further, the
resulting blend exhibits significant improvements in the
tensile and falling dart impact properties, and greater
resistance to undergoing delamination near the gate,
without sacrifice to the chemical resistance, in
comparison with the same amount of polyethylene alone
in the conventional blend.
The property differences in articles prepared
from the above mentioned compositions are illustrated in
- 3 - 8CN 8187
the examples.
Description of the Invention
Briefly, the present invention is a thermo-
plastic composition comprising:
(a~ a polyphenylene ether resin, alone, or
together with one or more alkenyl aromatic polymers; and
(b~ a minor amount of a combination of (i) a
copolymer of ethylene and methacrylic acid and (ii~ a
copolymer of styrene and glycidyl methacrylate, the
10 combination providing comparable chemical resistance but
better moldability than the same amount of polyethylene.
The term "moldability" as used here is defined
by the degree of delamination near the gate area of the
molded part. The term "better" means less delamination.
The term "minor amount" is used in this
disclosure to refer to less than 50 percent by weight,
in this case based on 100 percent by weight of
components (a) and (b) combined.
The polyphenylene ethers (also known as
20 polyphenylene oxides) used in the present invention
are a well known class of polymers which have become
very useful commercially as a result of -the discovery
by Allan S. Hay of an efficient and economical method
of production (see, for example, U.S. Patents 3,306,874
25 and 3,306,875, both issued February 28, 1967 to Hay).
Numerous modifications and variations have since been
developed but, in general, they are characteri~ed as a
class by the presence of arylenoxy structural units.
The present invention includes all such variations and
30 modifications, including but not limited to those
described hereinafter.
The polyphenylene ethers favored for use in
the practice of this invention generally contain
structural units of the following formula
- 4 - 8CN 8187
Q2 Ql
_ ~ O
Q Ql
in which in each of these units independently each Ql
is hydrogen, halogen, primary or secondary lower alkyl
(i.e., alkyl containing up to 7 carbon atoms), phenyl
haloalkyl or aminoalkyl wherein at least two carbon
atoms separate the halogen or nitrogen atom from the
benzene ring, hydrocarbonoxy, or halohydrocarbonoxy
wherein at least two carbon atoms separate the halogen
and oxygen atoms; and each Q2 is independently hydrogen,
halogen, primary or secondary lower alkyl, phenyl,
haloalkyl, hydrocarbonoxy or halohydrocarbonoxy as
defined for Ql Examples of suitable primary lower
alkyl groups are methyl, ethyl, n-propyl, n-butyl,
isobutyl, n-amyl, isoamyl, 2-methylbutyl, n-hexyl,
2,3-dimethylbutyl, 2-,3-, or 4-methylpentyl and the
corresponding heptyl groups. Examples of secondary
lower alkyl groups are isopropyl, sec-butyl and
3-pentyl. Preferrably, any alkyl radicals are straight
chain rather than branched. Most often, each Ql is
2a alkyl or phenyl, especially Cl 4 alkyl, and each Q2 is
hydrogen.
Both homopolymers and copolymers are included.
Suitable homopolymers are those containing, for example,
2,6-dimethyl-1,4-phenylene ether units. Suitable
copolymers lnclude random copolymers containing such
units in combination with, for example, 2,3,6-trimethyl-
1,4-phenylene ether units. Many suitable random
copolymers, as well as homopolymers, are disclosed in
the patent literature, including various Hay U.S.
patents. Also contemplated are graft copolymers,
including those prepared by grafting onto the poly-
phenylene ether chain such vinyl monomers as
~2~ 3
~ 5 - 8CN 8187
acrylonitrile and vinyl aromatic compounds (for example,
styrene), and such polymers as polystyrenes and elastomers.
Still other suitable polyphenylene ethers are the coupled
polyphenylene ethers in which the coupling agent is
reacted with the hydroxy groups of the two polyphenylene
ether chains to increase the molecular weight of the
polymer. Illustrative of the coupling agents are low
molecular weight polycarbonates, quinones, heterocycles
and formals.
The polyphenylene ether generally has a
molecular weight (number average, as determined by
gel permeation chromatography, whenever used herein)
within the range of about 5,000 to 40,000. The intrinsic
viscosity of the polymer is usually in the range oE
about 0.45 to 0.5 deciliters per gram (dl.~g.), as
measured in solution in chloroform at 25C.
The polyphenylene ethers may be prepared by
known methods, and typically by the oxidative coupling
coupling of at least one corresponding monohydroxy-
aromatic (e.g., phenolic) compound. A particularlyuseful and readily available monohydroxyaromatic
compound is 2,6-xylenol (in which for the above formula
each Q is methyl and each Q is hydrogen), the corres-
ponding polymer of which may be characterized as a
poly(2,6-dimethyl-1,4-phenylene ether).
Any of the various catalyst systems known
in the art to be useful for the preparation of
polyphenylene ethers can be used in preparing those
employed in this invention. For the most part, they
contain at least one heavy metal compound, such as
a copper, manganese or cobalt compound, usually in
combination with various other materials.
Among the preferred catalyst systems are
those containing copper. Such catalysts are disclosed,
for example, in the aforementioned U.S. Patents
3,306,874 and 3,306,875, and elsewhere. They are
- 6 - 8CN 8187
usually combinations of cuprous or cupric ions, halide
ions (i.e., chloride, bromide or iodide), and at least
one amine.
Also preferred are catalyst systems containing
manganese. They are generally alkaline systems containing
divalent manganese and such anions as halide, alkoxide
or phenoxide. Most often, the manganese is present as
a complex with one or more complexing and/or chelating
agents such as dialkylamines, alkanolamines, alkylene-
diamines, o-hydroxyaromatic aldehydes, o-hydroxyazo
compounds,~J-hydroxyoximes (both monomeric and polymeric),
o-hydroxyaryl oximes, and ~-diketones. Also useful are
cobalt-containing catalyst systems. Those skilled in
the art will be familiar with patents disclosing manganese
and cobalt-containing catalyst systems for polyphenylene
ether preparation.
Especially useful polyphenylene ethers for
the purposes of this invention are those which comprise
molecules having at least one of the end groups of
formulas II and III, below, in which Q and Q are as
previously defined, each Rl is independently hydrogen or
alkyl, providing that the total number of carbon atoms
in both Rl radicals is ~ or less, and each R2 is
independently hydrogen or a Cl 6 primary alkyl radical.
Preferably, each Rl is hydrogen and each R2 is alkyl,
especially methyl or n-butyl.
N(Rl)2
Q2 C(R )2
~ OH (II)
Q2 Ql
Ql Q2 Q2 Ql
OH (III)
Ql Q2 Q2 Ql
6~
- 7 - 8CN 8187
Polymers containing the aminoalkyl-substituted
end groups of ~ormula II may be obtained by incorporating
an appropriate primary or secondary monoamine as one of
the constituents of the oxidative coupling reaction
rnixture, especially when a copper- or manganese-containing
catalyst is used. Such amines, especially the dialkyl-
amines and preferably di-n-butylamine and dimethylamine,
frequently become chemically bound to the polyphenylene
ether, most often by replacing one of the ~-hydrogen atoms
on one or mole Ql radical adjacent to the hydroxy group
on the terminal unit of the polymer chain. During further
processing and/or blending, the aminoalkylsubstituted
end groups may undergo various reactions, probably involving
a quinone methide-type intermediate of formula IV, below
(Rl is defined as above), with beneficial effects often
including an increase in impact strength and compatibiliza-
tion with other blend components.
C(R )2
~ / ~ O (IV)
Polymers with biphenol end groups of formula III
are typically obtained from reaction mixtures in which
a by-product diphenoquinone of formula V, below, is
present, especially in a copper-halide-secondary or
tertiary amine system. In this regard, the disclosures
of the U.S. Patent 4,234,706, issued November 18, 1980
25 to White, U.S. Patent 4,477,649, issued October 16, 1984
_o Mobley and U.S. Patent 4,482,697, issued November 13,
1984 to Haiko are particularly pertinent. In mixtures
of this type, the diphenoquinone is ultimately incorporated
into the polymer in substitantial amounts, chiefly as
an end group.
- 8 - 8CN 8187
Ql Q2 Q2 Ql
o~O (V)
In many polyphenylene ethers obtained under
the conditions described above, a substantial proportion
of the polymer molecules, usually as much as about 90%
by weight of the polymer, contain end groups having one
of frequently both of formulas II and III. It should be
understood, however, that other end groups may be present
and that the invention in its broadest sense may not be
dependent on the molecular structures of the polyphenylene
ether end groups.
It will thus be apparent to those skilled in
the art that a wide range of polymeric materials
encompassing the full recognized class of polyphenylene
ether resins are contemplated as suitable for use in the
practice of the present invention.
The polyphenylene ether resin may be used
alone, or together with one or more alkenyl aromatic
polymers and/or copolymers typically associated with
such resins. The alkenyl aromatic polymers useful in
the practice of this invention include non-rubber
modified poly(alkenyl aromatic) homopolymers, rubber
modified poly(alkenyl aromatic) resins, and alkenyl
aromatic copolymers and terpolymers, modified or
unmodified with rubber.
In general, these alkenyl aromatic polymers,
which may be characterized as resins in some cases and
rubbers in other cases, are derived in whole or in part
from alkenyl aromatic compounds having the formula
CRl = CHR2
'~
r ~ (R )n
- 9 - 8CN 8187
where Rl and R2 are selected from the group consisting
of lower alkyl and alkenyl groups having from 1 to 6
carbon atoms, and hydrogen; each R3 is selected
independently from the group consisting of hydrogen,
chloro, bromo, and lower alkyl groups having from 1 to
6 carbon atoms; and n represents the total number of
R3 substituents on the ring, the same or different,
and is an integer from 1 to 5.
Compounds within the above formula include,
but are not limited to, styrene, alpha-methyl styrene,
para-methyl styrene, 2,~-dimethyl styrene, chloro-
styrenes (mono-, di-, tri-, etc.), para-tert-butyl
styrene, para-ethyl styrene, and the like.
Most preferred for this invention is
polystyrene, including unmodified and rubber modified
polystyrene resins, as well as copolymers of styrene
with one or more other monomer, such as butadiene.
These may be used singly or in combination in the
parent compositions.
The rubber modified polystyrene resins
suitable to use herein include those commonly referred
to in the art as high lmpact polystyrenes, or HIPS.
Typically, these are derived by adding rubber during
or after -the polymerization of the styrene monomer, -to
give a mixture, interpolymer, or both~ depending on
the procedure. Examples of suitable rubber modifiers
include polybutadiene, polyisoprene, polychloroprene,
ethylene-propylene-diene (EPDM) rubber, ethylene-
propylene copolymers (EPR), polyurethanes, and poly-
organosiloxanes (silicone rubbers or elastomers). Anyof these is permissible in the context of this invention.
Also useful are thermoplastic linear, graft
and radial block copolymers of styrene with other
monomers, and especially with rubbery precursors, such
as butadiene. These include various types in which one
or more polymeric styrene units alternate or vary randomly
- 10 - 8CN 8187
with one or more other polymeric units, e.g., poly-
butadiene, or in which the polystyrene has been grafted
onto a rubbery backbone polymer. Most especially, these
will be materials which serve as impact strength improvers
to upgrade this property in articles prepared from the
compositions. Suitable commercial materials include
various Kraton~ rubbers manufactured by Shell Chemical
Company and the Stereon ~ products of FIRESTONE Co.
The polyphenylene ether resins and poly-
(alkenyl aromatics), including mixtures of two or morealkenyl aromatic polymers, are utilizable in the present
compositions in virtually all proportions, for instance,
from 99:1 to 1:99 parts by weight ratio based on 100
parts by weight of these two types of polymers combined.
The polymer which constitutes component (b~(i)
of the present compositions is essentially a random
copolymer containing both ethylene units and methyl
acrylic (methacrylic) acids units in the polymer
chain. More specificall7, the copolymer is characterized
by units of the following formulae:
~ CH2 -- CH2 )
and CH3
~ CH2 -- C
COOH
Preferably, this copolymer will have a
methacrylic acid content in the range of 5 to 40 percent
by weight.
These copolymers may be prepared by
conventional methods, such as by the reaction of ethylene
with methacrylic acid in an organic solvent, for example,
benzene, in the presence of a free radical generating
compound, for example, benzoyl peroxide. The reaction
may be carried out at the boiling point of the solvent,
with refluxing, and if desired at superatmospheric
6~
11 - 8CN 8187
pressures to further facilitate the copolymerization.
Random copolymers of ethylene and methacrylic
acid suitable for use in the practice o-f this invention
are also available commercially from The DuPont Company
under the trade mark Nucrel resins.
The polymer which constitutes component (b)(ii)
of the present compositions, serving in combination with
(b)(i) is a copolymer of styrene and glycidyl methacrylate
characterized by units of the following formulae:
( CH2 - - CH
and CH3
( CH2 -- C
C = O
o
C,H2
C~
Preferably, this copolymer will have a
glycidyl methacrylate content in the range of 5 to 50
percent by weight.
Preparation of such copolymers is similar
to that of styrene-methyl methacrylate copolymer
formation, except of course for the use of glycidyl
methacrylate as a comonomer in place of methyl
methacrylate. Thus, for instance, glycidyl methacrylate
is polymerized alone or with an alkyl acrylate, for
example, butyl acrylate, followed by polymerization of
styrene monomer in the presence of the glycidyl
methasrylate polymer or copolymer.
Typically, copolymer (b)(ii) will contain
6~3
- 12 - 8CN 8187
less than 50 percent by weight of glycidyl methacrylate
units and, correspondingly, greater than 50 percent by
weight of styrene units.
Preferred embodiments of the present invention
will be formulated to be within certain favored ranges
of material amounts which are as follows:
Amount,
Ingredients Parts by Weight
Polyphenylene ether resin 95 to 5
10 High impact polystyrene resin 5 to95
100 Total
Styrene-ethylene/butylene-styrene
block copolymer 1 to 20
Ethylene-methacrylic acid copolymer 1 to 40
Styrene-glycidyl methacrylatecopolymer 0.1 to 10
per each 100 parts of the above two resins combined.
In most cases, effective results are
obtained with the use of just very small amounts of
component (b)(ii), and typically the composition of
the invention will contain a major amount of (b`)(i)
and a minor amoun-t of (b)(ii), rela-tive to one another.
As mentioned, polyethylene, while not necessary,
can be included in the composition if desired. Only
relatively small amounts are contemplated and, in
general, the amount used should be low enough such
that the total weight of the polyethylene combined
with components (b)(i) and (b)(ii) does not exceed 40
parts by weight, per 100 parts by weight of (a) and (b).
The present compositions are often formulated
to also contain supplementary ingredients, including
those which beneficially affect chemical and physical
properties of the compositions during and after molding.
These are generally selected from among additives or
auxiliary materials, both polymeric and non-polymeric,
which are conventionally employed in polyphenylene ether
resin compositions. Among them are mineral fillers (for
- ~o~
- 13 - 8CN 8187
example, clay, mica or talc), reinforcing agents or
fillers (for example, glass fibers, flakes or spheres),
plasticizers, lubricants, antioxidants, stabilizers,
colorants (for example, dyes or pigments), flame retardant
agents, electrically conductive materials (for example,
carbon blacks), melt viscosity reducers, and so forth.
Typically, these materials are utilized in conventional
amounts for achieving their known functions, usually
varying from about 1 to about 50 parts by weight, based
on 100 parts by weight of the total composition.
For applications where greater fire
resistance is desired, one or more flame retardant
agents may be added in the usual amounts. Of particular
current interest are bromine compounds and higher
molecular weight brominated or bromine-containing flame
retardant agents, such as bromostyrene oligomers or
polymers, both homopolymeric and copolymeric. They may
be supplemented with known flame retardant synergists,
for example, antimony oxide, in small amounts.
The composition is prepared by any
conventional methods, and normally by dry or solution
blending the ingredients to form a homogeneous mixture.
For greater convenience, it is often advantageous to
form the mixture into pellets or tablets, and -this
can be done by extruding the mixture and thereafter
cutting or chopping the extrudate down to size. The
pellets or tablets can then be injection molded into
the desired article, including any of -those for which
polyphenylene ether resin compositions are known to be
useful.
Descrip'tion of the''Spec'if'ic' Embodiments
The compositions and articles of
this invention are further illustrated in the
following examples, which are provided to show
best or preferred embodiments.
J~
~ 8CN 8187
EXAMPLES 1-5
The compositions shown in Table 1
were prepared by forming a preblend of the ingredients
at room temperature, extruding the preblend through
a twin-screw 28mm Werner Pfleiderer extruder at
290 rpm using the temperature profile
350/450/500/550/550/550F., and injection molding
into test pieces using a 3 ounce Newbury injection
molding machine under a pressure of 10,000 psi,
a melt temperature of 545F. and a mold temperature
of 150F. A prior art comparison is included~ The
results are shown in the Table 1.
It is clear that replacement of the low
density polyethylene in the comparison blends by
poly(ethylene-co-methacrylic acid) and poly-
(styrene-co-glycidyl methacrylate) results in
significant improvements in the Dynatup impact
strength, the tensile strength, the elongation,
and the resistance to delamination near the gate,
without notable sacri~ice in the chemical
resistance ~Examples 5 and 6). The blend
compositions comprising the combination o~ low
density polyethylene~ poly(ethylene-co-methacrylic
acid) and poly(styrene-co-glycidyl methacryla-te),
Examples 1, 2 and 3, also exhibit improved
performance over the comparison blend. However,
their resistances to delamination near the gate
are not as good as Examples 5 and 6.
7:~
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- 15 - 8CN 8187
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- 16 - 8CN 8187
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- 17 - 8CN 8187
The invention may be modified from the
particular embodiments shown without departing from
the scope and principles and without sacrificing the
chief benefits.
