Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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POTY~T~ CO~PO~ITIONS
This invention relates to novel polyester compositions
and insulated electrical conductors, especially insulated
wires for use as lead wires in refrigeration systems and
other hermetically sealed electrical apparatus (often called
"hermetic lead wires").
Many polyester compositions are known, including
compositions which can be melt-shaped, e.g. melt-extruded
around a conductor to provide an insulating coating.
Reference may be made for example to United States Patent
Nos. 2,167,278, 3,671,487, 3,835,089, 4,048,128, 4,332,855,
4,767,668, 4,483,970 and 5,248,713, and International
Publication Nos. 94/16014 and 96/02591. The disclosure of
each of said publications is incorporated herein by
reference.
In conventional hermetic lead wires, the lnsulatlon ls
a wrapped polyester tape sandwiched between two polyester
fiber braids. Such insulation is expensive and difficult to
apply. U.S. Patent No. 5,225,635 (Wake et al.) discloses a
hermetic lead wire in which the insulation comprises an
insulating layer made by melt-extruding a composition
containing chlorosulfonated polyethylene, an acid acceptor,
a filler, and a peroxide crosslinking agent.
We have discovered, in accordance with the present
invention, that very useful compositions can be made by
modifying polytetramethylene terephthalate (also referred to
as PTMT, polybutylene terephthalate, and PBT) or a like
aromatic polyester by addition thereto of a second polymer
which has a recrystallization temperature greater than 150~C
~ and is a polyester block copolymer. Such compositions have
an excellent combination of resistance to deterioration by
refrigerants and retention of physical properties when
subjected to heat aging, and are particularly suitable for
use as insulation on hermetic lead wires.
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In a first preferred aspect, this invention provides a
polymeric composition which comprises
(1) a thermoplastic aromatic polyester which consists
essentially of 70 to 100% by weight of
tetramethylene terephthalate units and 0 to 30% of
other units which are randomly copolymerized with
the tetramethylene terephthalate units, and
(2) a second polymer which has a recrystallization
temperature greater than 150~C and is a polyester
lo block copolymer;
the ratio by weight of the second polymer (2) to the
aromatic polyester (1) being from 0.05:1 to 0.35:1.
In a second preferred aspect, the invention provides an
insulated electrical device which comprises a metal
conductor, preferably a wire, and an insulating jacket
comprising a melt-shaped layer of a composition according to
the first preferred aspect of the invention.
In a third preferred aspect, the invention provides an
electrical assembly which comprises a hermetically sealed
enclosure containing a refrigerant liquid and an insulated
electrical conductor within the enclosure and contacted by
the refrigerant, wherein said conductor is as defined in the
second preferred aspect of the invention.
The invention is chiefly described herein by reference
to thermoplastic polyester compositions which can be melt
shaped, preferably melt extruded around a conductor, e.g. a
solid or stranded wire, to provide an insulating coating
around the wire. Generally the wire size is 4 to 38 AWG,
preferably 10 to 30 AWG. When the wire is to be used as a
hermetic lead wire, it is preferably a stranded wire. The
term "coating" is used herein to denote a coating which is
the sole insulating coating around the conductor; or a
coating which is one of several insulating coatings around
the conductor (the polyester composition being the innermost
coating, or the outermost coating, or an intermediate
coating or two or more of these coatings); or an insulating
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jacket around two or more conductors each having an
individual insulating coating around it. The thickness of
the coating is generally 0.05 to 0.8 mm (0.002 to 0. 030
inch), preferably 0.08 to 0.4 mm (0. 003 to 0.015 inch).
However, it is to be understood that the invention is also
applicable to other melt-shaped configurations, e.g. tubing
and molded parts, and to compositions which can be shaped in
other ways, and to compositions whose prime function is not
to provide electrical insulation.
lo Parts and percentages given in this specification are
by weight unless otherwise noted.
The A~om~t;c Polyester
Component (1) of the composition is an aromatic
polyester which contains 70 to 100~, preferably 95 to 100~,
particula~rly 100~, by weight of tetramethylene terephthalate
units, and in which any other units are randomly
copolymerized with the tetramethylene terephthalate units.
Such other units can be, for example, other alkylene
terephthalate units, e.g. ethylene terephthalate units, or
aliphatic polyester units.
The Polyester Rl ock Copolymer
The polyester block copolymer used in this invention is
preferably a thermoplastic elastomer (TPE) comprising
aromatic polyester blocks and aliphatic polyester blocks.
The melting point of the TPE is preferably greater than
170~C, particularly greater than 180~C, especially greater
than 200~C. The percentage by weight of aromatic polyester
blocks is generally 10 to 90~, preferably 37 to 90~,
particularly 70 to 90~. The aromatic and aliphatic
polyester blocks can be linked together, for example,
through ester groups and/or urethane groups, for example
through a urethane group of the formula
-O-(CH2)n-OOC.NH.Ar.CH2.Ar.NH.CO-
where n is 2 to 6, preferably 4, and Ar is an aromatic
radical, preferably 1,4-phenylene.
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The repeating units in the aromatic polyester blocks
have the formula
-O-(CH2)p-O.CO.Ar.CO-
where p is at least 2, preferably 2 to 6, particularly 4,
and Ar is an arylene group, preferably a 1,4-phenylene
group. Preferably all the repeating units are the same,
especially tetramethylene terephthalate units.
The repeating units in the aliphatic polyester blocks
have the formula
-O- (CH2) q~O~ CO~ (CH2) r~CO
wherein each of q and r, which may be the same or different,
is at least 2, preferably 2 to 6, particularly 4.
Preferably all the repeating units are the same.
Suitable block polyesters are available from DSM
Engineering Plastics under the trade name "Arnitel", e.g.
Arnitel UM550, UM551, and UX4854, and are described in U.S.
Patent No. 4,483,970 (Huntjens et al., assigned to Akzo
N.V.), the disclosure of which is incorporated herein by
reference.
Rel~t;ve Amol~nts of TP~ ~n~ ~omat;c Polyester
The ratio by weight of the polyester block copolymer to
the aromatic polyester is preferably 0.05:1 to 0.35:1,
particularly 0.15:1 to 0.30:1, especially 0.22:1 to 0.27:1.
Other Po1ymer;c Ingre~;ents
The polymeric component of the compositions preferably
consists essentially of the polyester block copolymer and
the aromatic polyester, but can also contain one or more
other polymers (e.g. other polyesters, including
homopolymers and random and block copolymers, such as
polyethylene terephthalate), preferably in amount less than
20~, particularly less than 10~, based on the weight of the
TPE.
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Non-Polymeric Ingre~-ents
The compo~itions can contain non-polymeric ingredients,
generally in amount less than 20~, preferably less than 10~,
particularly less than 4~, by weight based on the weight of
the composition. Such additives can be inorganic or
organic, and include antioxidants, stabilizers, processing
aids, coloring agents, fillers and flame retardants,
including antimony trioxide, e~g. in amount 3-15~, and
brominated flame retardants, e.g. in amount 5 to 15~. For
lo further details of suitable additives, reference may be made
to the documents incorporated herein by reference.
For use on hermetic lead wires, the composition
preferably has less than 0.8~, particularly less than 0.6~,
especially less than 0.35~ extractables when subjected to
the Freon extraction test described below. Such
compositions can for example be obtained by blending an
aromatic polyester which has less than 0.3~ extractables
with a polyester block copolymer which has more than 1.2
extractables in the Freon extraction test. When the
hermetic lead wire is to be used with a refrigerant which is
not Freon 22, the composition preferably has a similarly low
level of extractables in a test which is the same as the
Freon extraction test except that the Freon 22 is replaced
by the refrigerant actually used.
The melt-extruded insulating jacket preferably has an
initial elongation of at least 200~, particularly at least
300~, especially at least 360~, and an elongation of at
least 200~, particularly at least 300~, especially at least
360~, after aging for 168 hours at 156~C.
~ MPT.l~..S
The invention is illustrated by the following Examples,
which are summarized in the Table below. In the Table, the
following abbreviations are employed. TPE 1 is the TPE sold
by DSM Englneering Plastics under the trade name Arnitel
UX4854. TPE 2 is the TPE sold by DSM Engineering Plastics
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under the tradename Arnitel UM551V. Arnitel UX4854 and
UM551V are believed to be TPE's as defined above in which Ar
is a phenylene group, each of p, q and r is 4, and the
aromatic and aliphatic polyester blocks are linked together
through a urethane group of the formula
--O-(CH2)4--OOC. NH.Ar.CH2.Ar.NH CO--
where Ar is 1,4-phenylene.
PBT is the polybutylene terephthalate sold by Hoechst
Celanese under the trade name Celanex 1600A. WT10, BK10,
RD10, RD11, and OR10 are the color concentrates sold by
Wilson Color Inc. under the tradenames Wilson-89-WT-10,
Wilson-89-BK-10, Wilson-89-RD-10, Wilson-89-RD-11, and
Wilson-89-OR-10, respectively.
In each of the Examples, the ingredients and amounts
thereof shown in Table 1 were mixed together and melt
extruded as an insulating jacket of the wall thickness (in
mils) shown in the Table over a stranded copper wire of the
diameter (in mils) shown in the Table. The resulting
insulated wire was tested to determine one or more of its
Heat Aging, Extractables, Elongation and Tensile Strength.
The procedures used in these tests are described below. The
results are shown in the Table.
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Res;st~nce to H~t Ag;ng is measured by the method of ASTM D
3032, Section 14. The results given are the average times
to ~ailure (in hours) for ten specimens aged at the
indicated temperature. The Table also includes estimated
minimum times for aging at 125~C (with 18k etc. meaning
18,000 hours etc).
~xtr~ct~hles is measured by the CFC Extraction Test
described in NEMA Publication MW1000, paragraph 3.55.
~lo~at;on~ ~n~ Tens;le Strength are measured by the method
of ASTM D 3032, Section 14, both initially and after aging
for 168 hours at 156~C ("aged" in Table).
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TABLE
F~y~r~NQ
In~re-
dients 1 2 3 _ 5 6 1 8 2 10
PBT 78 78 78 78 78 78 845 845 845 84S
TPE 1 20 20 20 20 20 20 ~
TPE 2 -- -- -- -- -- -- 125 125 125 125
WT10 2 -- -- 2 -- -- 3
BK10 -- 2 -- -- 2 -- -- 3 -- --
RD10 -- -- -- -- -- 2 -- -- -- 3
RDll -- -- 2 -- -- -- -- -- 3
OR10
Wire
Diameter1~5 125 1.25 125 125 125 125 125 125 125
mm (mil)(49) (49) (49) (49) (49) (49) (49) (49) (49) (49)
Wall
Thickness02 02 02 0.4 0.4 0.4 0.4 0.4 0.4 0.4
mm (mil)(8) (8) (8) (16) (16) (16) (16) (16) (16) (16)
Heat Agin~
at
190~C 139 126 165 132 134 117
1 80~C 266 252 273 285 271 256
170~C 534 508 534 516 525 511
Est.
Min. at
125~C 18k l9k llk 18k 18k 24k
Extraç-
tables
R22 028 029 028 OA 05 0.4 05
R134A 03 02 05 0.1
Elonga-
tion %
Initial364 374 379 438 452 440 390 398 400 408
Aged 401 405 411 495 495 487 436 436 415 360
Tensile
S~
Initial
kg/cm2500 507 508 678 692 666 572 596 608 624
(psi)(7098)(n40)(72S8)(g680)(9891)(9Sl9) (8176)(8515)(8685)(8911)
Aged
kg/cm2524 518 520 653 653 620 592 581 560 459
(psi)(7480)(7402)(7431)(9328)(9328)(8855) (8460)(8297)(8007)(6562)
SUBSTITUTE SHEET (RULE 26)
