U.S. patent application number 11/763658 was filed with the patent office on 2007-10-11 for conductive thermoplastic composition.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Robert Hossan, Sai-Pei Ting.
Application Number | 20070235699 11/763658 |
Document ID | / |
Family ID | 33449418 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070235699 |
Kind Code |
A1 |
Hossan; Robert ; et
al. |
October 11, 2007 |
CONDUCTIVE THERMOPLASTIC COMPOSITION
Abstract
Disclosed herein is a method of making conductive thermoplastic
compositions, particularly conductive poly(arylene ether)/polyamide
compositions using a conductive masterbatch, whereas the conductive
masterbatch is made by a method comprising mixing conductive carbon
black and a first resin to form a conductive carbon black/resin
mixture; and compounding the conductive carbon black/resin mixture
with a second resin, wherein the first resin is a powder.
Inventors: |
Hossan; Robert; (Delmar,
NY) ; Ting; Sai-Pei; (Schenectady, NY) |
Correspondence
Address: |
CANTOR COLBURN LLP - GE PLASTICS-NORYL
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
33449418 |
Appl. No.: |
11/763658 |
Filed: |
June 15, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10250023 |
May 29, 2003 |
7241403 |
|
|
11763658 |
Jun 15, 2007 |
|
|
|
Current U.S.
Class: |
252/511 |
Current CPC
Class: |
C08L 71/12 20130101;
C08L 77/02 20130101; C08J 3/226 20130101; C08L 77/02 20130101; C08L
77/02 20130101; C08L 77/06 20130101; C08L 71/123 20130101; C08L
2205/02 20130101; C08L 77/00 20130101; C08L 71/123 20130101; C08J
2477/00 20130101; C08L 77/00 20130101; C08J 2371/12 20130101; C08L
2205/03 20130101; C08L 77/06 20130101; C08L 77/06 20130101; C08L
77/00 20130101; C08L 2666/14 20130101; C08K 3/04 20130101; C08L
2666/14 20130101; C08L 2666/14 20130101; C08L 2666/22 20130101;
C08L 2666/22 20130101; C08L 2666/22 20130101; C08L 2666/20
20130101 |
Class at
Publication: |
252/511 |
International
Class: |
C08G 69/00 20060101
C08G069/00 |
Claims
1. A thermoplastic composition made by a method comprising: dry
mixing conductive carbon black and a first polyamide resin, to form
a conductive carbon black/first polyamide mixture; compounding the
conductive carbon black/first polyamide resin mixture with a second
polyamide to form a conductive masterbatch; compounding a
poly(arylene ether) resin with a compatibilizer to form a
functionalized poly(arylene ether); compounding the functionalized
poly(arylene ether) with a third polyamide resin and the conductive
masterbatch wherein the first polyamide resin is a powder having a
particle size of 20 micrometers to 4 millimeters.
2. The thermoplastic composition of claim 1 wherein the
functionalized poly(arylene ether) is compounded with the
conductive masterbatch prior to compounding with the third
polyamide resin.
3. The thermoplastic composition of claim 1 wherein the
compatibilizer is selected from the group consisting of citric
acid, fumaric acid and maleic acid.
4. The thermoplastic composition of claim 1 wherein the first
polyamide resin is polyamide 6,6.
5. The thermoplastic composition of claim 1 wherein the first and
second polyamide resins are both in powder form having a particle
size less than 600 micrometers.
6. The thermoplastic composition of claim 1 wherein the second
polyamide resin is in pellet form and has a particle size greater
than 600 micrometers.
7. The thermoplastic composition of claim 1 wherein the first and
second polyamide resins are chemically identical.
8. The thermoplastic composition of claim 1 wherein the first and
second polyamide resins are chemically different.
9. The thermoplastic composition of claim 1 wherein the conductive
carbon black has a particle size less than 200 nanometers.
10. The thermoplastic composition of claim 1 wherein the conductive
masterbatch comprises 4 to 16 weight percent conductive carbon
black and 84 to 96 weight percent polyamide resin, based on the
total weight of the conductive masterbatch.
11. The thermoplastic composition of claim 1 wherein the surface
volume resistivity is greater than 9,600 kilo-ohm-cm.
12. The thermoplastic composition of claim 1 further comprising
compounding an impact modifier with the poly(arylene ether) and
compatibilizer.
13. The thermoplastic composition of claim 12 wherein the impact
modifier comprises a polystyrene-polybutadiene-polystyrene block
copolymer.
14. The thermoplastic composition of claim 12 wherein the Izod
impact strength is greater than or equal to 54 kJ/m.sup.2 as
determined according to ISO 180.
15. The thermoplastic composition of claim 12, wherein the
thermoplastic composition has a Dynatup impact strength greater
than 150% of the Dynatup impact strength of a comparable
thermoplastic composition made using a first polyamide resin having
a particle size greater than 4 millimeters and further wherein the
Dynatup impact strengths are determined according to ASTM 256 at
23.degree. C.
16. The thermoplastic composition of claim 12 wherein the
thermoplastic composition has an Izod impact strength greater than
300% of the Izod impact strength of a comparable thermoplastic
composition made using a first polyamide resin having a particle
size greater than 4 millimeters, and further wherein the Izod
impact strengths are determined according to ISO 180.
17. The thermoplastic composition of claim 12 wherein the melt
viscosity is greater than or equal to 276 Pascal-seconds as
determined by DIN54811.
18. A thermoplastic composition comprising 10 to 70 weight percent
poly(arylene ether); 30 to 90 weight percent of combined polyamide
resin; up to 25 weight percent compatibilizer; and up to 20 weight
percent of one or more impact modifiers, based on the total weight
of the composition.
19. The thermoplastic composition of claim 18, wherein the Izod
impact strength is greater than or equal to 54 kJ/m.sup.2 as
determined by ISO 180; the surface volume resistivity is greater
than or equal to 9,600 kilo-ohm-cm; the Dynatup impact strength is
greater than or equal to 38 J as determined by ASTM 256; and the
melt viscosity is greater than or equal to 276 Pascal-seconds as
determined by DIN54811.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/250,023 filed on May 29, 2003 which is incorporated by
reference herein.
BACKGROUND OF INVENTION
[0002] This disclosure relates to a method of making conductive
thermoplastic compositions, particularly conductive poly(arylene
ether)/polyamide compositions.
[0003] Conductive carbon black has been successfully used in
combination with a variety of thermoplastic resins to form
conductive thermoplastic compositions. However, the formation of
these conductive thermoplastic compositions can be challenging due
to the low bulk density of conductive carbon black. One approach
has been to form a concentrate or masterbatch containing a
thermoplastic resin and conductive carbon black and then adding the
concentrate to the thermoplastic composition. While this approach
is an improvement in making conductive thermoplastic compositions,
difficulties still remain in the formation of the conductive
masterbatch due to the low bulk density of conductive carbon black.
Accordingly, further improvements in the methods of making
conductive masterbatches and conductive thermoplastic compositions
are needed.
SUMMARY OF INVENTION
[0004] Disclosed herein is a method of making a conductive
masterbatch comprising mixing conductive carbon black and a first
resin to form a conductive carbon black/resin mixture; compounding
the conductive carbon black/resin mixture with a second resin,
wherein the first resin is a powder having a particle size of about
20 micrometers to about 4 millimeters.
[0005] In another embodiment a method of making a conductive
thermoplastic composition comprises mixing conductive carbon black
and a first resin to form a conductive carbon black/resin mixture;
compounding the conductive carbon black/resin mixture with a second
resin to form a conductive masterbatch and compounding the
conductive masterbatch with a third resin and an optional fourth
resin, wherein the first resin is a powder having a particle size
of about 20 micrometers to about 4 millimeters.
[0006] Also disclosed herein is a thermoplastic composition made by
a method comprising dry mixing conductive carbon black and a first
polyamide resin to form a conductive carbon black/polyamide
mixture; compounding the conductive carbon black/polyamide resin
mixture with a second polyamide to form a conductive masterbatch;
compounding a poly(arylene ether) with a compatibilizer to form a
functionalized poly(arylene ether); compounding the functionalized
poly(arylene ether) with a third polyamide resin and the conductive
masterbatch.
[0007] The above and other features are exemplified by the
following detailed description.
DETAILED DESCRIPTION
[0008] Disclosed herein is a method of making a conductive
masterbatch. The method comprises mixing conductive carbon black
and a first resin to form a conductive carbon black/resin mixture
and compounding the conductive carbon black/resin mixture with a
second resin to form the masterbatch. The first resin is in powder
form and acts as a flow promoter, facilitating the addition of the
low bulk density conductive carbon black to the compounding device.
The powdered first resin also facilitates subsequent compounding.
The first and the second resins may both be in powder form or the
second resin may be in pellet form. Similarly the first and second
resin may be chemically identical or different. In one embodiment
the first and second resins are polyamide resins. A thermoplastic
composition may be made by adding the conductive masterbatch to one
or more thermoplastic resins or resin blends. Thermoplastic
compositions made with the conductive masterbatch exhibit improved
conductivity when compared to similar compositions made without the
conductive masterbatch.
[0009] Suitable conductive carbon blacks are those capable of
modifying the conductive properties of a thermoplastic resin or
composition. Such carbon blacks are commercially available and are
sold under a variety of trade names, including, but not limited to,
S.C.F. (Super Conductive Furnace), E.C.F. (Electric Conductive
Furnace), Ketjen Black EC (available from Akzo Co., Ltd.) or
acetylene black. Preferred carbon blacks are those having average
particle sizes less than or equal to about 200 nanometer (nm), more
preferably less than or equal to about 100 nm, and most preferably
less than or equal to about 50 nm. Preferably conductive carbon
blacks may also have surface area greater than or equal to about
200 square meter per gram (m.sup.2/g), more preferably greater than
or equal to about 400 m.sup.2/g, and most preferably greater than
or equal to about 1000 m.sup.2/g. Preferred conductive carbon
blacks may have a pore volume (dibutyl phthalate absorption)
greater than or equal to about 40 cubic centimeters per hundred
grams (cm.sup.3/100 g), more preferably greater than or equal to
about 100 cm.sup.3/100 g, and most preferably greater than or equal
to about 150 cm.sup.3/100 g.
[0010] The conductive masterbatch comprises about 4 weight percent
(wt %) to about 16 wt percent (wt %) conductive carbon black based
on the total weight of the conductive masterbatch. Within this
range, the masterbatch preferably comprises greater than or equal
to about 5 wt % conductive carbon black, with greater than or equal
to about 6 wt % conductive carbon black more preferred, and greater
than or equal to about 8 wt % conductive carbon black especially
preferred. Also with in this range, the masterbatch preferably
comprises less than or equal to about 16 wt % conductive carbon
black, with less than or equal to about 14 wt % conductive carbon
black more preferred, and less than or equal to about 12 wt %
conductive carbon black especially preferred.
[0011] Suitable resins for use in the conductive masterbatch
include polycarbonate; poly(arylene ether); poly(alkenyl aromatic);
polyolefins; diene derived polymers such as polybutadiene and
polyisoprene; polyacrylamide; polyamides; polyesters;
polyestercarbonates; polyethersulfones; polyetherketones;
polyetherimides; copolymers thereof; copolymers of alkenyl aromatic
compounds and acrylonitrile; blends of two or more of the
foregoing; and the like.
[0012] As mentioned above the conductive carbon black is combined
with a resin in powder form. The resin powder has a particle size
of about 20 micrometers to about 4 millimeters. Within this range
the particle size is preferably greater than or equal to about 50,
more preferably greater than or equal to about 100 and most
preferably greater than or equal to about 150 micrometers. Also
within this range the particle size is preferably less than or
equal to about 2, more preferably less than or equal to about 1.5
and most preferably less than or equal to about 1 millimeters.
Particle size, as defined herein, refers to the maximum size of the
particle, although some particles may be smaller, as when a
material is sifted through a sieve with a particular mesh size.
[0013] Preferably one or more of the resins employed in the
masterbatch comprise polyamide. Polyamide resins include a generic
family of resins known as nylons, characterized by the presence of
an amide group (--C(O)NH--). Nylon-6 and nylon-6,6 are the
generally preferred polyamides and are available from a variety of
commercial sources. Other polyamides, however, such as nylon-4,6,
nylon-12, nylon-6,10, nylon 6,9, nylon 6/6T and nylon 6,6/6T with
triamine contents below about 0.5 weight percent, as well as
others, such as the amorphous nylons may be useful in the
conductive masterbatch and the thermoplastic composition. Mixtures
of various polyamides, as well as various polyamide copolymers, are
also useful. An especially preferred polyamide is
polyamide-6,6.
[0014] Polyamides can be obtained by a number of well known
processes such as those described in U.S. Pat. Nos. 2,071,250;
2,071,251; 2,130,523; 2,130,948; 2,241,322; 2,312,966; and
2,512,606. Nylon-6, for example, is a polymerization product of
caprolactam. Nylon-6,6 is a condensation product of adipic acid and
1,6-diaminohexane. Likewise, nylon 4,6 is a condensation product
between adipic acid and 1,4-diaminobutane. Besides adipic acid,
other useful diacids for the preparation of nylons include azelaic
acid, sebacic acid, dodecane diacid, as well as terephthalic and
isophthalic acids, and the like. Other useful diamines include
m-xylyene diamine, di-(4-aminophenyl)methane,
di-(4-aminocyclohexyl)methane; 2,2-di-(4-aminophenyl)propane,
2,2-di-(4-aminocyclohexyl)propane, among others. Copolymers of
caprolactam with diacids and diamines are also useful.
[0015] The conductive masterbatch may contain about 84 wt % to
about 96 wt % of resin based on the total weight of the conductive
masterbatch. Within this range, the masterbatch preferably
comprises less than or equal to about 95 wt % resin, more
preferably less than or equal to about 94 wt % resin, and most
preferably less than or equal to about 92 wt % resin. Also within
this range, the masterbatch preferably comprises greater than or
equal to about 83 wt % resin, more preferably greater than or equal
to about 86 wt % resin, and most preferably greater than or equal
to about 88 wt % resin.
[0016] The conductive masterbatch is made by mixing the conductive
carbon black with powdered resin to form a conductive carbon
black/resin mixture and then compounding the conductive carbon
black/resin mixture with additional resin. The additional resin may
be in powdered or pellet form. Additionally, the additional resin
may be chemically identical to or different from the powdered
resin. The conductive carbon black/resin mixture and the additional
resin may be added to a melt mixing device simultaneously or
sequentially. Preferably they are added sequentially, even more
preferably the conductive carbon black/resin mixture is added to
the melt mixing device after the additional resin.
[0017] In an exemplary embodiment, polyamide is added to the
feedthroat of an extruder, the conductive carbon black is dry
blended with powdered polyamide to form the conductive carbon
black/polyamide mixture, which is added via a feedport downstream
of the feedthroat. The weight ratio of the powdered polyamide to
the polyamide in pellet form is about 1:9 to about 9:1 and
preferably is about 2:8 to about 6:4 based on a 10 weight percent
loading of conductive carbon black in the masterbatch. After
compounding, the conductive masterbatch can be pelletized and added
to one or more thermoplastic resins or resin blends at a later time
or immediately added as a melt to one or more thermoplastic resins
or resin blends to form a conductive thermoplastic composition.
[0018] The conductive thermoplastic composition may comprise any
resin or combination of resins that is compatible with the
conductive masterbatch. Determining compatible resins is well
within the abilities of one of ordinary skill in the art.
[0019] When the conductive masterbatch comprises polyamide the
conductive thermoplastic composition preferably comprises
poly(arylene ether). The term poly(arylene ether) includes
polyphenylene ether (PPE) and poly(arylene ether) copolymers; graft
copolymers; poly(arylene ether) ether ionomers; and block
copolymers of alkenyl aromatic compounds, vinyl aromatic compounds,
and poly(arylene ether), and the like; and combinations comprising
at least one of the foregoing; and the like. Poly(arylene ether)
per se, are known polymers comprising a plurality of structural
units of the formula (I): ##STR1## wherein for each structural
unit, each Q.sup.1 is independently hydrogen, halogen, primary or
secondary lower alkyl (e.g., alkyl containing up to 7 carbon
atoms), phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy,
halohydrocarbonoxy wherein at least two carbon atoms separate the
halogen and oxygen atoms, or the like; and each Q.sup.2 is
independently hydrogen, halogen, primary or secondary lower alkyl,
phenyl, haloalkyl, hydrocarbonoxy, halohydrocarbonoxy wherein at
least two carbon atoms separate the halogen and oxygen atoms, or
the like. Preferably, each Q.sup.1 is alkyl or phenyl, especially
C.sub.1-4 alkyl, and each Q.sup.2 is hydrogen.
[0020] Both homopolymer and copolymer poly(arylene ether) are
included. The preferred homopolymers are those containing
2,6-dimethylphenylene ether units. Suitable copolymers include
random copolymers containing, for example, such units in
combination with 2,3,6-trimethyl-1,4-phenylene ether units or
copolymers derived from copolymerization of 2,6-dimethylphenol with
2,3,6-trimethylphenol. Also included are poly(arylene ether)
containing moieties prepared by grafting vinyl monomers or polymers
such as polystyrenes, as well as coupled poly(arylene ether) in
which coupling agents such as low molecular weight polycarbonates,
quinones, heterocycles and formals undergo reaction in known manner
with the hydroxy groups of two poly(arylene ether) chains to
produce a higher molecular weight polymer.
[0021] The poly(arylene ether) generally has a number average
molecular weight of about 3,000 to about 40,000 atomic mass units
(amu) and a weight average molecular weight of about 20,000 to
about 80,000 amu, as determined by gel permeation chromatography.
The poly(arylene ether) may have an intrinsic viscosity of about
0.10 to about 0.60 deciliters per gram (dl/g), preferably about
0.29 to about 0.48 dl/g, as measured in chloroform at 25.degree. C.
It is also possible to utilize a high intrinsic viscosity
poly(arylene ether) and a low intrinsic viscosity poly(arylene
ether) in combination. Determining an exact ratio, when two
intrinsic viscosities are used, will depend somewhat on the exact
intrinsic viscosities of the poly(arylene ether) used and the
ultimate physical properties that are desired.
[0022] The poly(arylene ether) are generally prepared by the
oxidative coupling of at least one monohydroxyaromatic compound
such as 2,6-xylenol or 2,3,6-trimethylphenol. Catalyst systems are
generally employed for such coupling; they typically contain at
least one heavy metal compound such as a copper, manganese or
cobalt compound, usually in combination with various other
materials.
[0023] Particularly useful poly(arylene ether) for many purposes
are those, which comprise molecules having one
aminoalkyl-containing end group. The aminoalkyl radical is
generally located in an ortho position to the hydroxy group.
Products containing such end groups may be obtained by
incorporating an appropriate primary or secondary monoamine such as
di-n-butylamine or dimethylamine as one of the constituents of the
oxidative coupling reaction mixture. Also frequently present are
4-hydroxybiphenyl end groups, generally obtained from reaction
mixtures in which a by-product diphenoquinone is present,
especially in a copper-halide-secondary or tertiary amine system. A
substantial proportion of the polymer molecules, typically
constituting as much as about 90% by weight of the polymer, may
contain said aminoalkyl-containing and 4-hydroxybiphenyl end
groups.
[0024] Based upon the foregoing, it will be apparent to those
skilled in the art that the contemplated poly(arylene ether) resin
may include many of those poly(arylene ether) resins presently
known, irrespective of variations in structural units or ancillary
chemical features.
[0025] The conductive thermoplastic composition comprises about 10
wt % to about 70 wt % poly(arylene ether) resin based on the total
weight of the conductive thermoplastic composition. Within this
range the composition preferably comprises greater than or equal to
about 10 wt % poly(arylene ether), more preferably greater than or
equal to about 20 wt % poly(arylene ether), and most preferably
greater than or equal to about 30 wt % poly(arylene ether). Also
within this range the composition preferably comprises less than or
equal to about 70 wt % poly(arylene ether), with less than or equal
to about 60 wt % poly(arylene ether) more preferred, and less than
or equal to about 50 wt % poly(arylene ether) especially
preferred.
[0026] In one embodiment, the conductive thermoplastic composition
is a blend of poly(arylene ether) resin and a polyamide resin as
described above. The polyamide resin may be the same or different
from the polyamide(s) employed in the conductive masterbatch. The
conductive thermoplastic composition comprises about 30 wt % to
about 90 wt % polyamide resin based on the total weight of the
conductive thermoplastic composition. Within this range the
composition preferably comprises greater than or equal to about 30
wt % polyamide, more preferably greater than or equal to about 35
wt % polyamide, and most preferably greater than or equal to about
40 wt % polyamide. Also within this range the composition
preferably comprises less than or equal to about 90 wt % polyamide,
with less than or equal to about 80 wt % polyamide more preferred,
and less than or equal to about 70 wt % polyamide especially
preferred.
[0027] When the conductive thermoplastic composition comprises
poly(arylene ether) and polyamide the composition may also comprise
a compatibilizer. A compatibilizer is a polyfunctional compound
that interacts with either the poly(arylene ether), the polyamide
resin, or both. This interaction may be chemical (e.g. grafting)
and/or physical (e.g. affecting the surface characteristics of the
dispersed phases). In either instance the resulting poly(arylene
ether)/polyamide composition appears to exhibit improved
compatibility, e.g., as may be evidenced by enhanced impact
strength, mold knit line strength and/or elongation. The
composition comprises about 0 wt % to about 25 wt % compatibilizer,
based on the total weight of the composition. The two-fold purpose
for using compatibilizer is to improve, in general, the physical
properties of the poly (arylene ether)/polyamide resin blend, as
well as to enable the use of a greater proportion of the
polyamide.
[0028] Examples of the various compatibilizers that may be employed
include: a) liquid diene polymers, b) epoxy compounds, c) oxidized
polyolefin wax, d) quinones, e) organosilane compounds, f)
polyfunctional compounds and functionalized poly(arylene ether) as
described obtained by reacting one or more of the previously
mentioned compatibilizing agents with poly(arylene ether)
hereinafter. The foregoing compatibilizers are more fully described
in U.S. Pat. Nos. 4,315,086; 4,600,741; 4,642,358; 4,826,933;
4,927,894; 4,980,424; 5,041,504; and 5,115,042.
[0029] The foregoing compatibilizers may be used alone or in
various combinations comprising one of these compatibilizers.
Furthermore, they may be added directly to the melt blend or
pre-reacted with either or both of the poly(arylene ether) and
polyamide, as well as with other materials employed in the
preparation of the composition. Where the compatibilizer is
employed in the preparation of the compositions, the initial amount
used will be dependent upon the specific compatibilizer chosen and
the specific amounts of poly(arylene ether) resin and polyamide
employed.
[0030] The conductive thermoplastic composition may further
comprise an impact modifier or combination of impact modifiers.
Particularly suitable thermoplastic impact modifiers are block
copolymers, for example, A-B diblock copolymers and A-B-A triblock
copolymers having one or two alkenyl aromatic blocks A, which are
typically styrene blocks, and a rubber block, B, which is typically
an isoprene or butadiene block. The butadiene block may be
partially hydrogenated. Mixtures of these diblock and triblock
copolymers are especially useful.
[0031] Suitable A-B and A-B-A copolymers include but are not
limited to polystyrene-polybutadiene,
polystyrene-poly(ethylene-propylene), polystyrene-polyisoprene,
poly(.alpha.-methylstyrene)-polybutadiene,
polystyrene-polybutadiene-polystyrene (SBS),
polystyrene-poly(ethylene-propylene)-polystyrene,
polystyrene-polyisoprene-polystyrene and
poly(alpha-methylstyrene)-polybutadiene-poly(alpha-methylstyrene),
as well as the selectively hydrogenated versions thereof, and the
like. Mixtures of the aforementioned block copolymers are also
useful. Such A-B and A-B-A block copolymers are available
commercially from a number of sources, including Phillips Petroleum
under the trademark SOLPRENE, Shell Chemical Co., under the
trademark KRATON, Dexco under the trademark VECTOR, and Kuraray
under the trademark SEPTON.
[0032] A useful amount of impact modifier is up to about 20 weight
percent (wt %), with about 5 wt % to about 15 wt % preferred, and
about 8 wt % to about 12 wt % especially preferred, wherein the
weight percentages are based on the entire weight of the
composition. In an especially preferred embodiment, the impact
modifier comprises a polystyrene-polybutadiene-polystyrene block
copolymer.
[0033] The conductive thermoplastic composition may further
comprise one or more additives. Possible additives include
anti-oxidants, drip retardants, dyes, pigments, colorants,
stabilizers, small particle mineral (e.g., clay, mica, talc, and
the like), antistatic agents, plasticizers, lubricants, and
combinations comprising at least one of the foregoing additives.
These additives are known in the art, as are their effective levels
and methods of incorporation. Effective amounts of the additives
vary widely, but they are usually present in an amount of less than
or equal to about 50 wt %, based on the total weight of the
composition. Especially preferred additives include hindered
phenols, thio compounds and amides derived from various fatty
acids. The preferred amount of these additives is generally about
0.25 wt % to about 2 wt %, based upon the total weight of the
composition.
[0034] The preparation of the conductive thermoplastic compositions
is achieved by merely blending the ingredients under conditions for
the formation of intimate blend. This can be achieved by various
techniques that employ kneader, mixer, single screw extruder, twin
screw extruder and the like.
[0035] All of the ingredients may be added initially to the
processing system, or some components may be precompounded. In one
embodiment the poly(arylene ether) resin, optional impact
modifier(s) and compatibilizer are added to the feedthroat of an
extruder and the polyamide resin and conductive masterbatch are fed
concurrently through a feedport downstream. In an alternative
embodiment the poly(arylene ether) resin, compatibilizers,
conductive masterbatch, optional impact modifier and some or all of
the polyamide are added in the feedthroat, and the remaining
portion of the polyamide, when present, is added downstream. While
separate extruders may be used in the processing, these
compositions are preferably prepared by using a single extruder
having multiple feedports along its length to accommodate the
addition of the various components. It is often advantageous to
apply a vacuum to the melt through at least one or more vent ports
in the extruder to remove volatile impurities in the composition.
Those of ordinary skill in the art will be able to adjust blending
times and temperatures, as well as component addition, without
undue additional experimentation.
[0036] It should be clear that compositions and articles made from
the compositions made by the method of this disclosure are within
the scope of the disclosure.
[0037] The disclosure is further illustrated by the following
non-limiting examples.
EXAMPLES 1-12
[0038] Conductive masterbatches containing 10 wt % conductive
carbon black (Ketjenblack.RTM. EC600JD, available from Akzo Nobel)
and 90 wt % polyamide (polyamide 6,6 available from DuPont) were
made using a Werner-Pfleiderer 30 millimeter twin-screw extruder
with ten barrels. The screw speed was 350 rotations per minute
(rpm). The temperature was about 250.degree. C. to 290.degree. C.
The stranding die was equipped with a two hole die plate. The
strands were cooled in a water bath and cut with a standard strand
pelletizer.
[0039] In example 1 all of the polyamide 6,6 was in pellet form and
the temperature was about 290.degree. C. In examples 2-6 ground
polyamide having a particle size less than or equal to about 600
micrometers was mixed with the conductive carbon black and the
conductive carbon black/polyamide mixture was added to the extruder
downstream. The temperature was 250.degree. C. In example 7 all
polyamide was added in pellet form at the extruder feedthroat and
the temperature was 250.degree. C. In examples 8-12 ground
polyamide was mixed with the conductive carbon black and the
conductive carbon black/polyamide mixture was added with the
polyamide pellets at the extruder feedthroat. The temperature was
250.degree. C. Relative amounts of the components in weight
percent, the mode of feed, the run rate in pounds per hour,
temperature profile in .degree. C. and observations on extrusion
are shown in Table 1. TABLE-US-00001 TABLE 1 Conductive Pellet
carbon Ground Run Temp Ex. polyamide black polyamide Rate Profile
Comment on Extrusion 1* 90 10 -- 30 290 feeder limitation,
struggling run 2 72 10 18 30 250 ran well 3 54 10 36 30 250 ran
well 4 36 10 54 20 250 ran well 5 18 10 72 18 250 ran at very slow
rate, plugged die later on 6 -- 10 90 -- 250 plugged die instantly
7* 90 10 -- -- 250 too fluffy to feed 8 72 10 18 -- 250 too fluffy
to feed 9 54 10 36 18 250 ran moderately well 10 36 10 54 -- 250
too fluffy to feed 11 18 10 72 -- 250 too fluffy to feed 12 -- 10
90 -- 250 too fluffy to feed *Comparative examples
[0040] Examples 1-12 demonstrate that combining conductive carbon
black powder and ground polyamide to form a conductive carbon
black/polyamide mixture improves the formation of the conductive
carbon black masterbatch, particularly when the carbon
black/polyamide mixture is added to the extruder downstream.
EXAMPLES 13-24
[0041] Conductive thermoplastic compositions using the
masterbatches prepared in examples 1-12 (herein referred to as
masterbatches 1-12) were prepared using an extruder. A dry blend
mixture containing 34.1 wt % of polyphenylene ether having an
intrinsic viscosity of 0.40 dl/g measured in chloroform at
25.degree. C., 8 wt % of an impact modifier (KG 1701 available from
Shell), 7 wt % of a second impact modifier (KG 1651 available from
Shell), 0.7 wt % citric acid, 0.3 wt % of a stabilizer (Irganox
1076 available from Ciba), 0.1 wt % potassium iodide and 0.01 wt %
copper iodide was added at the feedthroat of the extruder. A
mixture of 20 weight percent polyamide 6,6, 10 weight percent
polyamide 6 and 20 weight percent of a masterbatch as shown in
Table 2 was added at a second feeder located down stream of the
feedthroat.
[0042] The thermoplastic compositions were tested for Izod impact
strength according to ISO 180, Dynatup impact strength at
23.degree. C. according to ASTM 256, and melt viscosity (MV) at
282.degree. C. and 1500 seconds.sup.-1 according to DIN54811. The
test results are shown in Table 2. Izod impact values are in
kilojoules per square meter. Dynatup impact strength values are in
Joules. Surface volume resistivity values are in
kilo-ohm-centimeters and melt viscosity values are in
Pascal-seconds. Surface volume resistivity (SVR) was tested by the
following method. Tensile bars (ISO 527) were scored at both ends
with a knife and cooled in freezer (2 hr at -40.degree. C.). The
bars were cold fractured at the score marks to obtain brittle
fractures. Both ends were painted with conductive silverpaint (Du
Pont Electric 4817N) and the resistance was measured with a
multimeter. The read-out resistance was corrected for the
dimensions of the piece (length, width and thickness).
SVR=Resistivity measured*Fracture area (square centimeters)/length
(centimeters). Values reported in the Table 2 are an average of
five specimens tested. TABLE-US-00002 TABLE 2 Izod Dynatup Example
Masterbatch Impact Impact SVR MV 13* 1 16.1 22.8 Non-conductive 264
14 2 54.2 41.9 70 294 15 3 56.6 42.0 9,639 281 16 4 56.1 41.1
11,062 293 17 5 56.3 40.0 12,510 285 18 9 59.5 38.2 11,544 276
[0043] A comparison of the physical properties of Examples 13-18
indicates that the method of preparation of masterbatch has a
significant impact upon the properties of the conductive
thermoplastic composition. Notably, comparative Example 13 in which
the masterbatch was prepared using only polyamide in pellet form
exhibits markedly lower impact properties and conductivity than
Examples 14-18 in which the masterbatches were prepared using a
combination of powdered and pellet polyamide.
[0044] While the disclosure has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the discovery. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
discovery without departing from essential scope thereof.
Therefore, it is intended that the disclosure not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this discovery, but that the discovery will include
all embodiments falling within the scope of the appended
claims.
[0045] All cited patents, patent applications, and other references
are incorporated herein by reference in their entirety.
* * * * *