U.S. patent application number 14/658463 was filed with the patent office on 2015-07-02 for thermally conductive polymer compositions and articles made therefrom.
The applicant listed for this patent is Ticona LLC. Invention is credited to Yuji Saga.
Application Number | 20150184056 14/658463 |
Document ID | / |
Family ID | 42751642 |
Filed Date | 2015-07-02 |
United States Patent
Application |
20150184056 |
Kind Code |
A1 |
Saga; Yuji |
July 2, 2015 |
Thermally Conductive Polymer Compositions and Articles Made
Therefrom
Abstract
Thermally conductive polymer compositions comprising polymer,
highly moisture resistant magnesium oxide, and filler having higher
aspect ratio than 5. The compositions are particularly useful for
metal/polymer hybrid parts.
Inventors: |
Saga; Yuji; (Tochigi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ticona LLC |
Florence |
KY |
US |
|
|
Family ID: |
42751642 |
Appl. No.: |
14/658463 |
Filed: |
March 16, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13383468 |
Oct 12, 2012 |
8980984 |
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PCT/IB2010/053332 |
Jul 21, 2010 |
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14658463 |
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61228171 |
Jul 24, 2009 |
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Current U.S.
Class: |
252/75 ; 252/74;
252/76 |
Current CPC
Class: |
C09K 5/14 20130101; C08K
2201/016 20130101; C08K 7/04 20130101; H05K 7/20481 20130101; C08K
3/01 20180101; C09K 19/3809 20130101; C08K 7/02 20130101; C09K
19/02 20130101; C08K 3/22 20130101; C09K 19/52 20130101 |
International
Class: |
C09K 5/14 20060101
C09K005/14 |
Claims
1. A thermally conductive polymer composition, comprising: (a)
about 15 to about 70 weight percent of thermoplastic polymer (b)
about 20 to about 60 weight percent of magnesium oxide and (c)
about 5 to about 50 weight percent of filler having an aspect ratio
greater than wherein said (b) magnesium oxide has a weight gain by
conditioning at 90.degree. C., 90% RH for 100 hours of less than
1%; and, wherein said polymer composition has a thermal
conductivity of at least 0.5 W/mK, the percentages being based on
the total weight of the composition.
2. The composition of claim 1, wherein one or more of said (c)
fillers are used, selected from the group consisting of glass
fibers, wallastonites, glass flakes, talc, mica, boron nitride,
titanium oxide fiber and alumina fiber.
3. The composition of claim 1, wherein one or more of said (c)
fillers is glass fibers.
4. The composition as recited in claim 1, wherein said (b)
magnesium oxide is coated with a coupling agent selected from
silane series, titanate series, zirconate series, aluminate series,
and zircoaluminate series.
5. The composition as recited in claim 1, wherein said (b)
magnesium oxide has a BET surface area of less than 3 square meters
per gram.
6. The composition as recited in claim 1, wherein one or more of
said (a) thermoplastic polymers are used, selected from the group
consisting of thermoplastic polyester, thermoplastic polyamide,
liquid crystalline polymer and polyarylene sulfide.
7. The composition as recited in claim 1, additionally comprising
0.01 to about 15 volume percent of at least one polymeric
toughening agent.
8. An article made from the composition of claim 1.
9. A metal/polymer hybrid article made with the composition of
claim 1.
10. An insulator of a stator core of motors or generators made of
the composition of claim 1.
11. A stator assembly encapsulated with the composition of claim 1.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims filing benefit of U.S.
Provisional Patent Application Ser. No. 61/228,171 having a filing
date of Jul. 24, 2009, incorporated herein by reference.
FIELD OF THE INVENTION
[0002] Thermally conductive polymer compositions comprising polymer
and combination of water resistant magnesium oxide with fillers
having high aspect ratio are useful as components for electric and
electronics devices which require thermal management.
BACKGROUND OF THE INVENTION
[0003] Because of their excellent mechanical and electrical
insulation properties, polymeric resin compositions are used in a
broad range of applications such as in automotive parts, electrical
and electronic parts, machine parts and the like. In many cases,
because of the design flexibility they permit, sealing capability
and their electrical insulation properties, polymer resin
compositions can be used as encapsulants, housings and frames for
electrical and electronics devices or motors. However, not only are
electrical insulation properties needed in the encapsulating
polymer compositions, but they also often need to have higher
thermal conductivities especially with the downsizing trend of some
electrical devices. Another important requirement for encapsulating
polymer compositions is that their Coefficients of Linear Thermal
Expansions (CLTEs) should be close to CLTEs of materials
encapsulated with the polymer compositions to retain seal integrity
while releasing heat generated by the encapsulated devices. In
general, higher loading with thermally conductive filler in polymer
leads to higher thermal conductivity and lower CLTE because the
fillers' CLTEs are often lower than polymers' CLTEs. However, high
filler loadings often decreases flow-ability of polymer
compositions in melt forming processes, and that can lead to
failure of sealing performance or damage of core devices
encapsulated with the polymer compositions. Another important
requirement for housings or frames is mechanical strength. Thus,
polymer composition having higher thermal conductivity,
electrically insulation, lower CLTE, higher mechanical strength and
good flowability is desired.
[0004] Japanese patent application publication 2006-282783
discloses a polymer composition comprising polyarylene sulfide and
fibrous filler and a moisture resistant magnesium oxide. However
the composition's moisture resistance under high temperature and
high pressure is not enough to be used under sever environment.
[0005] Japanese laid-open patent JP2008-1333382 discloses a polymer
composition comprising liquid crystalline polymer and titanium
oxide fiber and a moisture resistant magnesium oxide. However the
composition's moisture resistance under high temperature and high
pressure is not enough to be used under sever environment.
SUMMARY OF THE INVENTION
[0006] There is disclosed and claimed herein a thermally conductive
polymer composition, comprising: [0007] (a) about 15 to about 70
weight percent of thermoplastic polymer [0008] (b) about 20 to
about 60 weight percent of magnesium oxide and [0009] (c) about 5
to about 50 weight percent of filler having an aspect ratio greater
than 5.
[0010] wherein said (b) magnesium oxide has a weight gain by
conditioning at 90.degree. C., 90% RH for 100 hours of less than 1%
and, wherein said polymer composition has a thermal conductivity of
at least 0.5 W/mK
the percentages being based on the total weight of the
composition.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The composition of the present invention comprises (a) at
least one thermoplastic polymer, (b) highly moisture resistant
magnesium oxide, (c) filler having higher aspect ratio than 5.
[0012] (a) The thermoplastic polymer is the polymer matrix of the
composition, and in which one or more polymers are used in a
continuous phase. Useful thermoplastic polymers include
polycarbonates, polyolefins such as polyethylene and polypropylene,
polyacetals, acrylics, vinyls, fluoropolymers, polyamides,
polyesters, polysulfones, polyarylene sulfides, liquid crystal
polymers such as aromatic polyesters, polyetherimides,
polyamideimides, polyacetals, polyphenylene oxides, polyarylates,
polyetheretherketones (PEEK), polyetherketoneketones (PEKK), and
syndiotactic polystyrenes, and blends thereof.
[0013] Preferred polymers of this invention are polyesters,
polyamides, polyarylene sulfides and liquid crystal polymers
(LCPs).
[0014] More preferred thermoplastic polyesters of this invention
include polyesters having an inherent viscosity of 0.3 or greater
and that are, in general, linear saturated condensation products of
diols and dicarboxylic acids, or reactive derivatives thereof.
Preferably, they will comprise condensation products of aromatic
dicarboxylic acids having 8 to 14 carbon atoms and at least one
diol selected from the group consisting of neopentyl glycol,
cyclohexanedimethanol, 2,2-dimethyl-1,3-propane diol and aliphatic
glycols of the formula HO(CH.sub.2).sub.nOH where n is an integer
of 2 to 10. Up to 20 mole percent of the diol may be an aromatic
diol such as ethoxylated bisphenol A, sold under the tradename
Dianol.RTM. 220 by Akzo Nobel Chemicals, Inc.; hydroquinone;
biphenol; or bisphenol A. Up to 50 mole percent of the aromatic
dicarboxylic acids can be replaced by at least one different
aromatic dicarboxylic acid having from 8 to 14 carbon atoms, and/or
up to 20 mole percent can be replaced by an aliphatic dicarboxylic
acid having from 2 to 12 carbon atoms. Copolymers may be prepared
from two or more diols or reactive equivalents thereof and at least
one dicarboxylic acid or reactive equivalent thereof or two or more
dicarboxylic acids or reactive equivalents thereof and at least one
diol or reactive equivalent thereof. Difunctional hydroxy acid
monomers such as hydroxybenzoic acid or hydroxynaphthoic acid or
their reactive equivalents may also be used as comonomers.
[0015] Preferred polyesters include poly(ethylene terephthalate)
(PET), poly(1,4-butylene terephthalate) (PBT), poly(1,3-propylene
terephthalate) (PPT), poly(1,4-butylene 2,6-naphthalate) (PBN),
poly(ethylene 2,6-naphthalate) (PEN), poly(1,4-cyclohexylene
dimethylene terephthalate) (PCT), and copolymers and mixtures of
the foregoing. Also preferred are 1,4-cyclohexylene dimethylene
terephthalate/isophthalate copolymer and other linear homopolymer
esters derived from aromatic dicarboxylic acids, including
isophthalic acid; bibenzoic acid; naphthalenedicarboxylic acids
including the 1,5-; 2,6-; and 2,7-naphthalenedicarboxylic acids;
4,4'-diphenylenedicarboxylic acid; bis(p-carboxyphenyl) methane;
ethylene-bis-p-benzoic acid; 1,4-tetramethylene bis(p-oxybenzoic)
acid; ethylene bis(p-oxybenzoic) acid; 1,3-trimethylene
bis(p-oxybenzoic) acid; and 1,4-tetramethylene bis(p-oxybenzoic)
acid, and glycols selected from the group consisting of
2,2-dimethyl-1,3-propane diol; neopentyl glycol; cyclohexane
dimethanol; and aliphatic glycols of the general formula
HO(CH.sub.2).sub.nOH where n is an integer from 2 to 10, e.g.,
ethylene glycol; 1,3-trimethylene glycol; 1,4-tetramethylene
glycol;-1,6-hexamethylene glycol; 1,8-octamethylene glycol;
1,10-decamethylene glycol; 1,3-propylene glycol; and 1,4-butylene
glycol. Up to 20 mole percent, as indicated above, of one or more
aliphatic acids, including adipic, sebacic, azelaic, dodecanedioic
acid or 1,4-cyclohexanedicarboxylic acid can be present. Also
preferred are copolymers derived from 1,4-butanediol, ethoxylated
bisphenol A, and terephthalic acid or reactive equivalents thereof.
Also preferred are random copolymers of at least two of PET, PBT,
and PPT, and mixtures of at least two of PET, PBT, and PPT, and
mixtures of any of the forgoing.
[0016] The thermoplastic polyester may also be in the form of
copolymers that contain poly(alkylene oxide) soft segments
(blocks). The poly(alkylene oxide) segments are present in about 1
to about 15 parts by weight per 100 parts per weight of
thermoplastic polyester. The poly(alkylene oxide) segments have a
number average molecular weight in the range of about 200 to about
3,250 or, preferably, in the range of about 600 to about 1,500.
Preferred copolymers contain poly(ethylene oxide) and/or
poly(tetramethylenether glycol) incorporated into a PET or PBT
chain. Methods of incorporation are known to those skilled in the
art and can include using the poly(alkylene oxide) soft segment as
a comonomer during the polymerization reaction to form the
polyester. PET may be blended with copolymers of PBT and at least
one poly(alkylene oxide). A poly(alkylene oxide) may also be
blended with a PET/PBT copolymer. The inclusion of a poly(alkylene
oxide) soft segment into the polyester portion of the composition
may accelerate the rate of crystallization of the polyester.
[0017] Preferred polyamides include semi-crystalline polyamide and
amorphous polyamide.
[0018] The semi-crystalline polyamide includes aliphatic or
semi-aromatic semi-crystalline polyamides.
[0019] The semi-crystalline aliphatic polyamide may be derived from
aliphatic and/or alicyclic monomers such as one or more of adipic
acid, sebacic acid, azelaic acid, dos decanedoic acid, or their
derivatives and the like, aliphatic C.sub.6-C.sub.20
alkylenediamines, alicyclic diamines, lactams, and amino acids.
Preferred diamines include bis(paminocyclohexyl)methane;
hexamethylenediamine; 2-methylpentamethylenediamine;
2-methyloctamethylenediamine; trimethylhexamethylenediamine;
1,8-diaminooctane; 1,9-diaminononane; 1,10-diaminodecane;
1,12-diaminododecane; and m-xylylenediamine. Preferred lactams or
amino acids include 11-aminododecanoic acid, caprolactam, and
laurolactam.
[0020] Preferred aliphatic polyamides include polyamide 6;
polyamide 6,6; polyamide 4,6; polyamide 6,10; polyamide 6,12;
polyamide 11; polyamide 12; polyamide 9,10; polyamide 9,12;
polyamide 9,13; polyamide 9,14; polyamide 9,15; polyamide 6,16;
polyamide 9,36; polyamide 10,10; polyamide 10,12; polyamide 10,13;
polyamide 10,14; polyamide 12,10; polyamide 12,12; polyamide 12,13;
polyamide 12,14; polyamide 6,14; polyamide 6,13; polyamide 6,15;
polyamide 6,16; and polyamide 6,13.
[0021] The semi-aromatic semi-crystalline polyamides are one or
more homopolymers, copolymers, terpolymers, or higher polymers that
are derived from monomers containing aromatic groups. Examples of
monomers containing aromatic groups are terephthalic acid and its
derivatives. It is preferred that about 5 to about 75 mole percent
of the monomers used to make the aromatic polyamide used in the
present invention contain aromatic groups, and it is still more
preferred that about 10 to about 55 mole percent of the monomers
contain aromatic groups.
[0022] Examples of preferred semi-crystalline semi-aromatic
polyamides include poly(m-xylylene adipamide) (polyamide MXD,6),
poly(dodecamethylene terephthalamide) (polyamide 12,T),
poly(decamethylene terephthalamide) (polyamide 10,T),
poly(nonamethylene terephthalamide) (polyamide 9,T), hexamethylene
adipamide/hexamethylene terephthalamide copolyamide (polyamide
6,T/6,6), hexamethylene terephthalamide/2-methylpentamethylene
terephthalamide copolyamide (polyamide 6,T/D,T); hexamethylene
adipamide/hexamethylene terephthalamide/hexamethylene
isophthalamide copolyamide (polyamide 6,6/6,T/6,I);
poly(caprolactam-hexamethylene terephthalamide) (polyamide 6/6,T);
and the like.
[0023] In the present invention, a semi-crystalline semi-aromatic
polyamide is preferred in terms of heat resistance, dimension
stability and moisture resistance at high temperature
[0024] Semi-crystalline semi-aromatic polyamides derived from
monomers containing aromatic groups are especially advantageous for
uses in applications that require a balance of properties (e.g.,
mechanical performance, moisture resistance, heat resistance, etc.)
in the polyamide composition as well as higher thermal
conductivity.
[0025] In the present invention, amorphous polyamides can be used
in the polymer composition without giving significant negative
influence on the properties. They are one or more homopolymers,
copolymers, terpolymers, or higher polymers that are derived from
monomers containing isophthalic acid and/or
dimethyldiaminodicyclohexylmethane groups.
[0026] In the preferred amorphous polyamide, the polyamide consists
of a polymer or copolymer having repeating units derived from a
carboxylic acid component and an aliphatic diamine component. The
carboxylic acid component is isophthalic acid or a mixture of
isophthalic acid and one or more other carboxylic acids wherein the
carboxylic acid component contains at least 55 mole percent, based
on the carboxylic acid component, of isophthalic acid. Other
carboxylic acids that may be used in the carboxylic acid component
include terephthalic acid and adipic acid. The aliphatic diamine
component is hexamethylene diamine or a mixture of hexamethylene
diamine and 2-methyl pentamethylene diamine and/or
2-ethyltetramethylene diamine, in which the aliphatic diamine
component contains at least 40 mole percent, based on the aliphatic
diamine component, of hexamethylene diamine.
[0027] Examples of preferred amorphous polyamides include
poly(hexamethylene terephthalamide/hexamethylene isophthalamide)
(polyamide 6,T/6,I), poly(hexamethylene isophthalamide) (polyamide
6,I), poly(metaxylylene isophthalamide/hexamethylene
isophthalamide) (polyamide MXD,I/6,I), poly(metaxylylene
isophthalamide/metaxylylene terephthalamide/hexamethylene
isophthalamide) (polyamide MXD,I/MXD,T/6,I/6,T), poly(metaxylylene
isophthalamide/dodecamethylene isophthalamide) (polyamide
MXD,I/12I), poly(metaxylylene isophthalamide) (polyamide MXD,I),
poly(dimethyldiaminodicyclohexylmethane
isophthalamide/dodecanamide) (polyamide MACM,I/12),
poly(dimethyldiaminodicyclohexylmethane
isophthalamide/dimethyldiaminodicyclohexylmethane
terephthalamide/dodecanamide) (polyamide MACM,UMACM,T/12),
poly(hexamethylene
isophthalamide/dimethyldiaminodicyclohexylmethane
isophthalamide/dodecanamide) (polyamide 6,I/MACM,I/12),
poly(hexamethylene isophthalamide/hexamethylene
terephthalamide/dimethyldiaminodicyclohexylmethane
isophthalamid/dimethyldiaminodicyclohexylmethane terephthalamide)
(polyamide 6,I/6,T/MACM,I/MACM,T), poly(hexamethylene
isophthalamide/hexamethylene
terephthalamide/dimethyldiaminodicyclohexylmethane
isophthalamid/dimethyldiaminodicyclohexylmethane
terephthalamide/dodecanamide) (polyamide 6,I/6,T/MACM,I/MACM,T/12),
poly(dimethyldiaminodicyclohexylmethane
isophthalamide/dimethyldiaminodicyclohexylmethane dodecanamide)
(polyamide MACM,I/MACM,12) and mixtures thereof.
[0028] When an amorphous polyamide is used, the semicrystalline
polyamide is present in about 40 to about 100 (and preferably about
70 to about 100) weight percent, based on the total amount of
semicrystalline and amorphous polyamide present.
[0029] Preferred polyarylene sulfide includes any polyarylene
sulfides so far as those belong to the category called a
polyarylene sulfide.
[0030] The polyarylene sulfide may be a straight-chain compound, a
compound having been subjected to treatment at high temperature in
the presence of oxygen to crosslink, a compound having some amount
of a crosslinked or branched structure introduced therein by adding
a small amount of a trihalo or more polyhalo compound, a compound
having been subjected to heat treatment in a non-oxidizing inert
gas such as nitrogen, or a mixture of those structures.
[0031] By a LCP is meant a polymer that is anisotropic when tested
using the TOT test or any reasonable variation thereof, as
described in U.S. Pat. No. 4,118,372, which is hereby incorporated
by reference. Useful LCPs include polyesters, poly(esteramides),
and poly(ester-imides). One preferred form of LCP is "all
aromatic", that is all of the groups in the polymer main chain are
aromatic (except for the linking groups such as ester groups), but
side groups which are not aromatic may be present.
[0032] The thermoplastic polymer (a) will preferably be present in
about 15 to about 70 weight percent, or more preferably about 20 to
about 50 weight percent, based on the total weight of the
composition.
[0033] Moisture resistance at high temperature of magnesium oxide
can be estimated by its weight gain in conditioning at 90.degree.
C., 90% RH for 100 hours. The weight gain of the magnesium oxide
(b) used in present invention is less than 1%, and more preferably
0.8%. If the weight gain is more than 1%, good PCT resistance is
difficult to obtain.
[0034] The shape of magnesium oxide (b) is usually spherical or
granular or irregular, and its aspect ratio is lower than 5. If the
aspect ratio is larger than 5, isotropically-high thermal
conductivity can not be gained in articles molded of the resin
composition. The particles or granules can have a broad particle
size distribution. Preferably, maximum particle size is less than
300 .mu.m, and more preferably less than 200 .mu.m. Preferably, BET
surface area is less than 3 square meters per gram, and more
preferably less than 2 for the reason that large surface area leads
to deterioration of moisture resistance of the polymer composition.
The particles which have multi-modal size distribution in their
particle size can also be used.
[0035] The surface of the magnesium oxide (b) can be processed with
a coupling agent, for the purpose of improving the interfacial
bonding between the magnesium oxide surface and the matrix polymer.
Examples of the coupling agent include silane series, titanate
series, zirconate series, aluminate series, and zircoaluminate
series coupling agents.
[0036] Useful coupling agents include metal hydroxides and
alkoxides including those of Group IIIa thru VIIIa, Ib, IIb, IIIb,
and IVb of the Periodic Table and the lanthanides. Specific
coupling agents are metal hydroxides and alkoxides of metals
selected from the group consisting of Ti, Zr, Mn, Fe, Co, Ni, Cu,
Zn, Al, and B. Preferred metal hydroxides and alkoxides are those
of Ti and Zr. Specific metal alkoxide coupling agents are titanate
and zirconate orthoesters and chelates including compounds of the
formula (I), (II) and (Ill):
##STR00001##
wherein
M is Ti or Zr;
[0037] R is a monovalent C.sub.1-C.sub.8 linear or branched alkyl;
Y is a divalent radical selected from --CH(CH.sub.3)--,
--C(CH.sub.3).dbd.CH.sub.2--, or --CH.sub.2CH.sub.2--; X is
selected from OH, --N(R.sup.1).sub.2, --C(O)OR.sup.3,
--C(O)R.sup.3, --CO.sub.2.sup.-A.sup.+; wherein R.sup.1 is a
--CH.sub.3 or C.sub.2-C.sub.4 linear or branched alkyl, optionally
substituted with a hydroxyl or interrupted with an ether oxygen;
provided that no more than one heteroatom is bonded to any one
carbon atom; R.sup.3 is C.sub.1-C.sub.4 linear or branched alkyl;
A.sup.+ is selected from NH.sub.4.sup.+, Li.sup.+, Na.sup.+, or
K.sup.+.
[0038] The coupling agent can be added to the filler before mixing
the filler with the resin, or can be added while blending the
filler with the resin. The additive amount of coupling agent is
preferably 0.1 through 5 wt % or more preferably 0.5 through 2 wt %
with respect to the weight of the filler. Addition of coupling
agent during the blending of the magnesium oxide with the resin has
the added advantage of improving the adhesiveness between the metal
used in the joint surface between the heat transfer unit or heat
radiating unit and the thermally conductive resin.
[0039] The magnesium oxide (b) will preferably be present in 20 to
60 weight percent, more preferably 35 to 55 weight percent, based
on the total weight of the composition.
[0040] The filler having higher aspect ratio than 5 used as
component (c) in the present invention includes glass fibers,
wallastonites, glass flakes, talc, mica, boron nitride, titanium
oxide fiber, alumina fibers, boron fibers, potassium titanate
whiskers, aluminum borate whiskers and zinc oxide whiskers.
[0041] Preferably, glass fibers, wallastonites, alumina fibers,
boron fibers, zinc oxide whiskers are selected as component (c),
and more preferably, glass fibers are used as component (c).
[0042] In the similar way processed on the surface of the magnesium
oxide (b), the surface of the filler (c) can be processed with a
coupling agent, for the purpose of improving the interfacial
bonding between the magnesium oxide surface and the matrix
polymer.
[0043] Component (c) will be present in 5 to 50 weight percent, or
preferably 10 to 40 weight percent, or more preferably 20 to 40
weight percent, based on the total volume of the composition. If
its content is less than 5 weight percent, enough mechanical
strength and low CLTE can't be obtained. If its content is more
than 40 weight percent, flow-ability of the resin composition gets
worse.
[0044] Preferably, the weight ratio of (b)/(c) is preferably
between 28/72 and 92/8, or more preferably between 40/60 and 85/15.
If the ratio is less than 28/72, thermal conductivity of the
composition will become low, and if the ratio is more than 92/8,
heat shock resistance of the composition will be deteriorated.
[0045] The polymeric toughening agent optionally used in the
present invention is any toughening agent that is effective for the
polymer used. When the thermoplastic polymer is a polyester, the
toughening agent will typically be an elastomer or has a relatively
low melting point, generally <200.degree. C., preferably
<150.degree. C. and that has attached to it functional groups
that can react with the thermoplastic polyester (and optionally
other polymers present). Since thermoplastic polyesters usually
have carboxyl and hydroxyl groups present, these functional groups
usually can react with carboxyl and/or hydroxyl groups. Examples of
such functional groups include epoxy, carboxylic anhydride,
hydroxyl (alcohol), carboxyl, and isocyanate. Preferred functional
groups are epoxy, and carboxylic anhydride, and epoxy is especially
preferred. Such functional groups are usually "attached" to the
polymeric toughening agent by grafting small molecules onto an
already existing polymer or by copolymerizing a monomer containing
the desired functional group when the polymeric tougher molecules
are made by copolymerization. As an example of grafting, maleic
anhydride may be grafted onto a hydrocarbon rubber using free
radical grafting techniques. The resulting grafted polymer has
carboxylic anhydride and/or carboxyl groups attached to it. An
example of a polymeric toughening agent wherein the functional
groups are copolymerized into the polymer is a copolymer of
ethylene and a (meth)acrylate monomer containing the appropriate
functional group. By (meth)acrylate herein is meant the compound
may be either an acrylate, a methacrylate, or a mixture of the two.
Useful (meth)acrylate functional compounds include (meth)acrylic
acid, 2-hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, and
2-isocyanatoethyl (meth)acrylate. In addition to ethylene and a
functional (meth)acrylate monomer, other monomers may be
copolymerized into such a polymer, such as vinyl acetate,
unfunctionalized (meth)acrylate esters such as ethyl
(meth)acrylate, n-butyl (meth)acrylate, and cyclohexyl
(meth)acrylate. Preferred toughening agents include those listed in
U.S. Pat. No. 4,753,980, which is hereby included by reference.
Especially preferred toughening agents are copolymers of ethylene,
ethyl acrylate or n-butyl acrylate, and glycidyl methacrylate.
[0046] It is preferred that the polymeric toughening agent used
with thermoplastic polyesters contain about 0.5 to about 20 weight
percent of monomers containing functional groups, preferably about
1.0 to about 15 weight percent, more preferably about 7 to about 13
weight percent of monomers containing functional groups. There may
be more than one type of functional monomer present in the
polymeric toughening agent. It has been found that toughness of the
composition is increased by increasing the amount of polymeric
toughening agent and/or the amount of functional groups. However,
these amounts should preferably not be increased to the point that
the composition may crosslink, especially before the final part
shape is attained.
[0047] The polymeric toughening agent used with thermoplastic
polyesters may also be thermoplastic acrylic polymers that are not
copolymers of ethylene. The thermoplastic acrylic polymers are made
by polymerizing acrylic acid, acrylate esters (such as methyl
acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate,
n-hexyl acrylate, and n-octyl acrylate), methacrylic acid, and
methacrylate esters (such as methyl methacrylate, n-propyl
methacrylate, isopropyl methacrylate, n-butyl methacrylate (BA),
isobutyl methacrylate, n-amyl methacrylate, n-octyl methacrylate,
glycidyl methacrylate (GMA) and the like). Copolymers derived from
two or more of the forgoing types of monomers may also be used, as
well as copolymers made by polymerizing one or more of the forgoing
types of monomers with styrene, acrylonitrile, butadiene, isoprene,
and the like. Part or all of the components in these copolymers
should preferably have a glass transition temperature of not higher
than 0.degree. C. Preferred monomers for the preparation of a
thermoplastic acrylic polymer toughening agent are methyl acrylate,
n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, n-hexyl
acrylate, and n-octyl acrylate.
[0048] It is preferred that a thermoplastic acrylic polymer
toughening agent have a core-shell structure. The core-shell
structure is one in which the core portion preferably has a glass
transition temperature of 0.degree. C. or less, while the shell
portion is preferably has a glass transition temperature higher
than that of the core portion. The core portion may be grafted with
silicone. The shell section may be grafted with a low surface
energy substrate such as silicone, fluorine, and the like. An
acrylic polymer with a core-shell structure that has low surface
energy substrates grafted to the surface will aggregate with itself
during or after mixing with the thermoplastic polyester and other
components of the composition of the invention and can be easily
uniformly dispersed in the composition.
[0049] Suitable toughening agents for polyamides are described in
U.S. Pat. No. 4,174,358. Preferred toughening agents include
polyolefins modified with a compatibilizing agent such as an acid
anhydride, dicarboxylic acid or derivative thereof, carboxylic acid
or derivative thereof, and/or an epoxy group. The compatibilizing
agent may be introduced by grafting an unsaturated acid anhydride,
dicarboxylic acid or derivative thereof, carboxylic acid or
derivative thereof, and/or an epoxy group to a polyolefin. The
compatibilizing agent may also be introduced while the polyolefin
is being made by copolymerizing with monomers containing an
unsaturated acid anhydride, dicarboxylic acid or derivative
thereof, carboxylic acid or derivative thereof, and/or an epoxy
group. The compatibilizing agent preferably contains from 3 to 20
carbon atoms. Examples of typical compounds that may be grafted to
(or used as comonomers to make) a polyolefin are acrylic acid,
methacrylic acid, maleic acid, fumaric acs id, itaconic acid,
crotonic acid, citraconic acid, maleic anhydride, itaconic
anhydride, crotonic anhydride and citraconic anhydride.
[0050] Preferred toughening agents for polyacetals include
thermoplastic polyurethanes, polyester polyether elastomers, other
functionalized and/or grafted rubber, and polyolefins that contain
polar groups that are either grafted to their backbones or were
incorporated by copolymerizing with a monomer that contained one or
more polar groups. Preferable comonomers are those that contain
epoxide groups, such as glycidyl methacrylate. A preferred
toughening agent is EBAGMA (a terpolymer derived from ethylene,
butyl acrylate, and glycidyl methacrylate).
[0051] When used, the optional polymeric toughening agent will
preferably be present in about 0.5 to about 15 weight percent, or
more preferably in about 2 to about 10 weight percent, based on the
total weight of the composition.
[0052] The compositions of this invention may optionally include
one or more plasticizers, nucleating agents, flame retardants,
flame retardant synergists, heat stabilizers, antioxidants, dyes,
pigments, mold release agents, lubricants, UV stabilizers, (paint)
adhesion promoters, fillers having aspect ratio of at most 5 other
than the magnesium oxide (b) and the like.
[0053] The compositions of the present invention are preferably in
the form of a melt-mixed or a solution-mixed blend, more preferably
melt-mixed, wherein all of the polymeric components are
well-dispersed within each other and all of the non-polymeric
ingredients are homogeneously dispersed in and bound by the polymer
matrix, such that the blend forms a unified whole. The blend may be
obtained by combining the component materials using any melt-mixing
method or by mixing components other than matrix polymer with
monomers of the polymer matrix and then polymerizing the monomers.
The component materials may be mixed to homogeneity using a
melt-mixer such as a single or twin-screw extruder, blender,
kneader, Banbury mixer, etc. to give a resin composition. Part of
the materials may be mixed in a melt-mixer, and the rest of the
materials may then be added and further melt-mixed until
homogeneous. The sequence of mixing in the manufacture of the
thermally conductive polymer resin composition of this invention
may be such that individual components may be melted in one shot,
or the filler and/or other components may be fed from a side
feeder, and the like, as will be understood by those skilled in the
art.
[0054] The composition of the present invention may be formed into
articles using methods known to those skilled in the art, such as,
for example, injection molding, blow molding, extrusion, press
molding. The present compositions are especially useful in
electrical and/or electronic devices, sometimes forming in a sense
metal/resin hybrids. Such articles can include those for use in
motor housings, lamp housings, lamp housings in automobiles and
other vehicles, electrical and electronic housings, insulation
bobbin which exist between coiled wire and magnetic inducible metal
core in stator of motors or generators, and housings which
substantially encapsulates the stator core of motors or generators.
Examples of lamp housings in automobiles and other vehicles are
front and rear lights, including headlights, tail lights, and brake
lights, particularly those that use light-emitting diode (LED)
lamps. Examples of application in electric devices are reflector
and frame of LED lights. The articles may serve as replacements for
articles made from aluminum or other metals in many
applications.
Examples
Compounding and Molding Methods
[0055] The polymeric compositions shown in Table 1 were prepared by
compounding in a 32 mm Werner and Pfleiderer twin screw extruder.
All ingredients were blended together and added to the rear of the
extruder except that the magnesium oxide and the fillers were
side-fed into a downstream barrel, Barrel temperatures were set at
about 320.degree. C. for HTN and 315.degree. C. for PPS.
[0056] The compositions were molded into ISO test specimens on an
injection molding machine for the measurement of mechanical
properties before and after PCT (Pressure Cooker Test), and into
plates of 1mm.times.16mm.times.16mmm size for measurements of
thermal conductivity and CLTE. Melt temperature were about
325.degree. C. and mold temperatures were about 150.degree. C.
[0057] For evaluating heat shock resistance, the compositions were
overmolded with 1 mm thickness on the SUS304 (stainless steel)
blocks of 48 mm.times.29 mm.times.8 mm size. Melt temperature were
about 325.degree. C. and mold temperatures and temperature of the
SUS blocks inserted in the mold were about 150.degree. C.
Testing Methods
[0058] Tensile strength and elongation were measured using the ISO
527-1/2 standard method. Flexural strength and modulus were
measured using the ISO178-1/2 standard method. Notched charpy
impact was measured using the ISO 179/1eA standard method. The
above tests were conducted at 23.degree. C.
[0059] PCT was conducted under 121.degree. C., 0.2 MPa for 100
hours.
[0060] CLTE in mold flow direction were determined on about center
portion of the plate in the temperature range from -40 to
150.degree. C. using ASTM D696 method.
[0061] Thermal conductivity was determined on the plate using Laser
Flash Method as described in ASTM E1461. Results are shown in Table
1.
[0062] Heat shock resistance was evaluated by heat cycles between
-40.degree. C. and 150.degree. C. for 1 hour at each temperature
with a thermal shock chamber TSA-101S, and measured number of
cycles till crack is generated on the compositions overmolded on
the SUS blocks. The compositions which did not crack through 300
cycles were judged as good, and those which cracked by 300 cycles
were judged as NG (for "not good").
The following terms are used in Table 1: HTN refers to Zytel.RTM.
HTN501, a polyamide6TDT manufactured by E.I. du Pont de Nemours and
Co., Wilmington, Del. PPS refers to Ryton.RTM. QA280N, a
polyarylene sulfide manufactured by Chevron Phillips Chemical
Company LP LCP refers to Zenite.RTM. 6000, a liquid crystalline
polymer manufactured by E.I. DuPont de Nemours and Co., Wilmington,
Del. 2,6-NDA refers to 2,6-napthalene dicarboxylic acid, available
from BP Amoco Chemical Company. Talc refers to talc KOSSAP.RTM. #10
that is surface modified with an amino-silane coupling agent
manufactured by Nippon Talc Co., Ltd. PED521 refers to Licowax
PED521 supplied from Clariant Japan.K.K. CS-8CP is a calcium
montanate supplied from Nitto Chemical Industry Co., ltd Rubber-1
refers to Staphyloid.RTM.1M-203, a core-shell type polymer
toughening agent, supplied from Ganz Chemical Co., Ltd. Rubber-2
refers to Elvaloy.RTM. EP4934, an ethylene/vinyl-acrylate/glycidyl
methacrylate terpolymer manufactured by E.I. DuPont de Nemours and
Co., Wilmington, Del. Ultranox 626A.RTM. is
bis(2,4-di-tert-butylphenyl pentaerythritol) diphosphite, supplied
from Chemtura Corporation. AO-80 refers to ADKSTAB AO-80, a
hindered phenol based antioxidant, supplied from ADEKA Corporation.
MgO-1 refers to RF98, a magnesium oxide manufactured by Ube
Material Industries, Ltd. The weight gain of the RF98 powder by
conditioning at 90.degree. C., 90% RH for 100 hours was 0.3%, and
its BET surface area was 0.09 square meters per gram. MgO-1m refers
to a RF98 processed with 1 weight % epoxy silane coupling agent,
Z6040 manufactured by Dow Corning Toray. MgO-2 refers to RF98HR, a
magnesium oxide manufactured by Ube Material Industries, Ltd. The
weight gain of the RF98HR powder by conditioning at 90.degree. C.,
90% RH for 100 hours was 0.1%, and its BET surface area was 3.1
square meters per gram. MgO-2m refers to a RF98HR processed with 1
weight % amino silane coupling agent, Z-6011 manufactured by Dow
Corning Toray. MgO-3 refers to Coolfiller.RTM. CF2-100A
manufactured by Tateho Chemical Industries Co., Ltd. The weight
gain of the CF2-100A was 1.3%. An average size of the CF2-100A is
about 25 .mu.m. GF-1 refers to FT756D, glass fibers manufactured by
Owens Corning Japan Ltd. Tokyo, Japan. Diameter of the FT756D is 10
.mu.m GF-2 refers to ECS03T-747H, glass fibers manufactured by
Nippon Electric Glass Co., Ltd. Owens Corning Japan Ltd. GF-3
refers to Vetrotex.RTM. 910EC10, glass fiber supplied by OCV Co.
f-SiO2 refers to FB940, a spherical fused silica manufactured by
Denki Kagaku Kogyo K.K. Aspect ratio of the FB940 is almost 1.
TABLE-US-00001 TABLE 1 Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1 HTN 21.5 21.5
21.5 21.5 2,6-NDA 0.4 0.4 0.4 0.4 Talc 1.0 1.0 1.0 1.0 PED521 0.1
0.1 0.1 0.1 Rubber-1 4.0 4.0 4.0 4.0 Ultranox 626A 0.1 0.1 0.1 0.1
AO-80 0.3 0.3 0.3 0.3 CS-8CP 0.1 0.1 0.1 0.1 MgO-1 37.7 MgO-2 37.7
37.7 MgO-2m 37.7 MgO-3 GF-1 34.8 34.8 34.8 f-SiO2 34.8 Thermal
conductivity (W/m .degree. K) 0.7 0.7 0.7 0.90 CLTE (ppm/.degree.
C.) 17 16 16 25 Heat shock resistance Good Good Good NG Tensile
strength (MPa) 81 97 110 56 Tensile strength after PCT (MPa) 55 12
40 0 Retention after PCT (%) 68 12 36 0 Tensile elongation (%) 1.0
1.1 1.2 0.9 Flexural Modulus (GPa) 15.3 15.9 15.7 9.9 N-Charpy
Impact (kJ/m2) 2.9 3.2 3.3 2.6 All ingredient quantities are given
in weight percent relative to the total weight of the
composition.
TABLE-US-00002 TABLE 2 Comp. Comp. Ex. 4 Ex. 5 Ex. 2 Ex. 3 PPS 29.0
29.0 29.0 29.0 Rubber-2 2.0 2.0 2.0 2.0 MgO-1 36.0 36.0 MgO-1m 36.0
MgO-3 36.0 GF-1 33.0 33.0 33.0 f-SiO2 33.0 Thermal conductivity
(W/m .degree. K) 0.6 0.5 0.4 0.8 CLTE (ppm/.degree. C.) 21 20 18 34
Heat shock resistance Good Good Good Ng Tensile strength (MPa) 87
96 105 58 Tensile strength after PCT (MPa) 37 54 28 19 Retention
after PCT (%) 42 56 27 32 Tensile elongation (%) 0.9 1.1 1.0 0.8
Flexural Modulus (GPa) 16.8 17.0 17.6 11.5 N-Charpy Impact (kJ/m2)
3.1 3.1 3.8 1.9 All ingredient quantities are given in weight
percent relative to the total weight of the composition.
* * * * *