U.S. patent application number 09/728920 was filed with the patent office on 2002-08-01 for thermoplastic silicone elastomers formed from polyester resins.
Invention is credited to Chorvath, Igor, Gross, Craig Steven, Gruszynski, Kenneth Gerard, Lee, Michael Kang-Jen, Liao, Jun, Nakanishi, Koji, Rabe, Richard Leroy, Romenesko, David Joseph.
Application Number | 20020103308 09/728920 |
Document ID | / |
Family ID | 24928804 |
Filed Date | 2002-08-01 |
United States Patent
Application |
20020103308 |
Kind Code |
A1 |
Chorvath, Igor ; et
al. |
August 1, 2002 |
THERMOPLASTIC SILICONE ELASTOMERS FORMED FROM POLYESTER RESINS
Abstract
The present invention, therefore, relates to a method for
preparing a thermoplastic elastomer, said method comprising: (I)
mixing (A) a thermoplastic resin comprising more than 50 percent by
volume of a polyester resin other than poly(butylene
terephthalate), said thermoplastic resin having a softening point
of 23.degree. C. to 300.degree. C., (B) a silicone elastomer
comprising (B') 100 parts by weight of a diorganopolysiloxane gum
having a plasticity of at least 30 and having an average of at
least 2 alkenyl groups in its molecule and, optionally, (B") up to
200 parts by weight of a reinforcing filler, the weight ratio of
said silicone elastomer (B) to said thermoplastic resin (A) being
greater than 35:65 to 85:15, (C) 0.01 to 5 parts by weight of a
stabilizer for each 100 parts by weight of said thermoplastic resin
and said silicone elastomer, (D) an organohydrido silicon compound
which contains an average of at least 2 silicon-bonded hydrogen
groups in its molecule and (E) a hydrosilation catalyst, components
(D) and (E) being present in an amount sufficient to cure said
diorganopolysiloxane (B'); and (II) dynamically curing said
diorganopolysiloxane (B').
Inventors: |
Chorvath, Igor; (Midland,
MI) ; Gross, Craig Steven; (Midland, MI) ;
Gruszynski, Kenneth Gerard; (Essexville, MI) ; Lee,
Michael Kang-Jen; (Midland, MI) ; Liao, Jun;
(Midland, MI) ; Nakanishi, Koji; (Ichihara-shi,
JP) ; Rabe, Richard Leroy; (Midland, MI) ;
Romenesko, David Joseph; (Midland, MI) |
Correspondence
Address: |
DOW CORNING CORPORATION CO1232
2200 W. SALZBURG ROAD
P.O. BOX 994
MIDLAND
MI
48686-0994
US
|
Family ID: |
24928804 |
Appl. No.: |
09/728920 |
Filed: |
December 4, 2000 |
Current U.S.
Class: |
525/446 |
Current CPC
Class: |
C08G 77/06 20130101;
C08K 5/36 20130101; C08L 67/02 20130101; C08L 67/02 20130101; C08L
83/00 20130101; C08K 5/16 20130101; C08L 83/04 20130101; C08K 5/04
20130101; C08K 5/0091 20130101; C08G 77/12 20130101; C08G 77/44
20130101; C08K 5/5419 20130101; C08G 77/20 20130101; C08L 83/04
20130101; C08L 2666/28 20130101; C08L 2666/14 20130101 |
Class at
Publication: |
525/446 |
International
Class: |
C08F 008/00 |
Claims
That Which is claimed is
1. A method for preparing a thermoplastic elastomer, said method
comprising: (I) mixing (A) a thermoplastic resin comprising more
than 50 percent by volume of a polyester resin other than
poly(butylene terephthalate), said thermoplastic resin having a
softening point of 23.degree. C. to 300.degree. C., (B) a silicone
elastomer comprising (B') 100 parts by weight of a
diorganopolysiloxane gum having a plasticity of at least 30 and
having an average of at least 2 alkenyl groups in its molecule and,
optionally, (B") up to 200 parts by weight of a reinforcing filler,
the weight ratio of said silicone elastomer to said thermoplastic
resin being greater than 35:65 to 85:15, (C) 0.02 to 5 parts by
weight of a stabilizer for each 100 parts by weight of said
thermoplastic resin and said silicone elastomer, said stabilizer
being selected from hindered phenols; thioesters; hindered amines;
2,2'-(1,4-phenylene)bis(4H-3, 1-benzoxazin-4-one); or
3,5-di-tert-butyl-4-hydroxybenzoic acid, hexadecyl ester, (D) an
organohydrido silicon compound which contains an average of at
least 2 silicon-bonded hydrogen groups in its molecule and (E) a
hydrosilation catalyst, components (D) and (E) being present in an
amount sufficient to cure said diorganopolysiloxane (B'); and (II)
dynamically curing said diorganopolysiloxane (B'), wherein at least
one property of the thermoplastic elastomer selected from tensile
strength or elongation is at least 25% greater than the respective
property for a corresponding simple blend wherein said
diorganopolysiloxane is not cured and said thermoplastic elastomer
has an elongation of at least 30%.
2. The method according to claim 1, wherein said polyester resin is
poly(ethylene terephthalate).
3. The method according to claim 1, wherein said polyester resin is
selected from poly(trimethylene terephthalate), poly(ethylene
naphthalate), poly(butylene naphthalate) or
poly(cyclohexylenedimethylene terephthalate).
4. The method according to claim 1, wherein the weight ratio of
said silicone elastomer (B) to said thermoplastic resin (A) is
greater than 35:65 to 75:25.
5. The method according to claim 1, wherein a pre-mix of components
(A) through (C) and, optionally, component (D) is first prepared at
a temperature below the softening point of said resin (A), said
catalyst (E) is subsequently added to said pre-mix at a temperature
above the softening point of said resin (A) and said
diorganopolysiloxane (B') is then dynamically vulcanized.
6. The method according to claim 1, wherein said
diorganopolysiloxane (B') is a gum selected from the group
consisting of a copolymer consisting essentially of
dimethylsiloxane units and methylvinylsiloxane units and a
copolymer consisting essentially of dimethylsiloxane units and
methylhexenylsiloxane units and said reinforcing filler (B") is a
fumed silica.
7. The method according to claim 6, wherein said organohydrido
silicon component (D) is selected from the group consisting of a
polymer consisting essentially of methylhydridosiloxane units and a
copolymer consisting essentially of dimethylsiloxane units and
methylhydridosiloxane units, having 0.5 to 1.7 weight percent
hydrogen bonded to silicon and having a viscosity of 2 to 500 mPa-s
at 25.degree. C. and said catalyst (E) is a neutralized complex of
platinous chloride and divinyltetramethyldisiloxane.
8. The method according to claim 7, wherein the weight ratio of
said silicone elastomer (B) to said resin (A) is 40:60 to
70:30.
9. The method according to claim 1, wherein said stabilizer is a
thioester selected from distearyl 3,3'-thiodipropionate,
dilauryl-3,3'-thiodipropio- nate or ditridecyl
3,3'-thiodipropionate.
10. The method according to claim 1, wherein said stabilizer is a
hindered amine selected from 1,6-hexanediamine,
N,N'-bis(2,2,6,6-pentamethyl-4-pip- eridinyl)-, polymers with
morpholine-2,4,6-trichloro-1,3,5-triazine; 1,6-hexanediamine,
N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-, polymers with
2,4,-dichloro-6-(4-morpholinyl)-1,3,5-triazine;
bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate;
bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate; dimethyl succinate
polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine ethanol; or
polymethyl (propyl-3-oxy-(2',2',6',6'-tetramethyl-4'-piperidinyl)
siloxane.
11. The method according to claim 1, wherein said stabilizer is
selected from 2,2'-(1,4-phenylene)bis(4H-3, 1-benzoxazin-4-one); or
3,5-Di-tert-butyl-4-hydroxybenzoic acid, hexadecyl ester.
12. The method according to claim 1, wherein said stabilizer is a
hindered phenol having at least one group of the formula 5in its
molecule, in which Q is a monovalent organic group having 1 to 24
carbon atoms selected from (i) hydrocarbon groups, (ii) hydrocarbon
groups which optionally contain heteroatoms selected from sulfur,
nitrogen or oxygen or (iii) halogen-substituted versions of (i) or
(ii), wherein the benzene ring of said formula may additionally be
substituted with at least one Q group.
13. The method according to claim 12, wherein said stabilizer is a
hindered phenol having at least one group of the formula 6in its
molecule, wherein R is an alkyl group having one to four carbon
atoms, R' is a hydrocarbon group having 4 to 8 carbon atoms and
wherein the benzene ring of said formula may be optionally further
substituted with a hydrocarbon group having 1 to 24 carbon
atoms.
14. The method according to claim 13, wherein said
diorganopolysiloxane (B') is a gum selected from the group
consisting of a copolymer consisting essentially of
dimethylsiloxane units and methylvinylsiloxane units and a
copolymer consisting essentially of dimethylsiloxane units and
methylhexenylsiloxane units and said reinforcing filler (B") is a
fumed silica.
15. The method according to claim 14, wherein said hindered phenol
is selected from
tetrakis(methylene(3,5-di-tert-butyl-4-hydroxy-hydrocinnama-
te))methane,
N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnama-
mide) or
1,1,3-Tris(2'-methyl-4'-hydroxy-5'-t-butylphenyl)butane.
16. The method according to claim 15, wherein the weight ratio of
said silicone elastomer (B) to said thermoplastic resin (A) is
40:60 to 70:30.
17. The method according to claim 1, wherein a fire retardant is
included in mixing step (I).
18. A thermoplastic elastomer prepared by the method of claim
1.
19. A thermoplastic elastomer prepared by the method of claim
2.
20. A thermoplastic elastomer prepared by the method of claim
3.
21. A thermoplastic elastomer prepared by the method of claim
4.
22. A thermoplastic elastomer prepared by the method of claim
5.
23. A thermoplastic elastomer prepared by the method of claim
6.
24. A thermoplastic elastomer prepared by the method of claim
7.
25. A thermoplastic elastomer prepared by the method of claim
8.
26. A thermoplastic elastomer prepared by the method of claim
9.
27. A thermoplastic elastomer prepared by the method of claim
10.
28. A thermoplastic elastomer prepared by the method of claim
11.
29. A thermoplastic elastomer prepared by the method of claim
12.
30. A thermoplastic elastomer prepared by the method of claim
13.
31. A thermoplastic elastomer prepared by the method of claim
14.
32. A thermoplastic elastomer prepared by the method of claim
15.
33. A thermoplastic elastomer prepared by the method of claim
16.
34. A thermoplastic elastomer prepared by the method of claim 17.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a thermoplastic elastomer
composition wherein a silicone gum and a stabilizer are dispersed
in a polyester resin and the silicone gum is dynamically vulcanized
in the resulting mixture.
BACKGROUND OF THE INVENTION
[0002] Thermoplastic elastomers (TPEs) are polymeric materials
which possess both plastic and rubbery properties. They have
elastomeric mechanical properties but, unlike conventional
thermoset rubbers, they can be re-processed at elevated
temperatures. This re-processability is a major advantage of TPEs
over chemically crosslinked rubbers since it allows recycling of
fabricated parts and results in a considerable reduction of
scrap.
[0003] In general, two main types of thermoplastic elastomers are
known. Block copolymer thermoplastic elastomers contain "hard"
plastic segments which have a melting point or glass transition
temperature above ambient as well as "soft" polymeric segments
which have a glass transition or melt point considerably below room
temperature. In these systems, the hard segments aggregate to form
distinct microphases and act as physical crosslinks for the soft
phase, thereby imparting a rubbery character at room temperature.
At elevated temperatures, the hard segments melt or soften and
allow the copolymer to flow and to be processed like an ordinary
thermoplastic resin.
[0004] Alternatively, a thermoplastic elastomer referred to as a
simple blend, or physical blend, can be obtained by uniformly
mixing an elastomeric component with a thermoplastic resin. When
the elastomeric component is also cross-linked during mixing, a
thermoplastic elastomer known in the art as a thermoplastic
vulcanizate (TPV) results. Since the crosslinked elastomeric phase
of a TPV is insoluble and non-flowable at elevated temperature,
TPVs generally exhibit improved oil and solvent resistance as well
as reduced compression set relative to the simple blends.
[0005] Typically, a TPV is formed by a process known as dynamic
vulcanization, wherein the elastomer and the thermoplastic matrix
are mixed and the elastomer is cured with the aid of a crosslinking
agent and/or catalyst during the mixing process. A number of such
TPVs are known in the art, including some wherein the crosslinked
elastomeric component can be a silicone polymer while the
thermoplastic component is an organic, non-silicone polymer (i.e.,
a thermoplastic silicone vulcanizate or TPSiV). In such a material,
the elastomeric component can be cured by various mechanisms
including radical, condensation and hydrosilylation method, but
each method has its limitations.
[0006] Arkles, in U.S. Pat No. 4,500,688, discloses
semi-interpenetrating networks (semi-IPNs) wherein a
vinyl-containing silicone fluid having a viscosity of 500 to
100,000 cS is dispersed in a conventional thermoplastic resin.
Arkles only illustrates these IPNs at relatively low levels of
silicone. The vinyl-containing silicone is vulcanized in the
thermoplastic during melt mixing according to a chain extension or
crosslinking mechanism which employs a silicon hydride-containing
silicone component. Typical thermoplastics mentioned include
polyesters, polyurethanes, styrenics, polyacetals and
polycarbonates. This disclosure is expanded by Arkles in U.S. Pat
No. 4,714,739 to include the use of hybrid silicones which contain
unsaturated groups and are prepared by reacting a
hydride-containing silicone with an organic polymer having
unsaturated functionality. Although Arkles discloses a silicone
fluid content ranging from 1 to 40 weight percent (1 to 60% in the
case of the '739 patent), there is no suggestion of any criticality
as to these proportions or to the specific nature of the organic
resin.
[0007] Crosby et al., in U.S. Pat No. 4,695,602, teach composites
wherein a silicone semi-IPN vulcanized via a hydrosilation reaction
is dispersed in a fiber-reinforced thermoplastic resin having a
high flexural modulus. The silicones employed are of the type
taught by Arkles, cited supra, and the composites are said to
exhibit improved shrinkage and warpage characteristics relative to
systems which omit the IPN.
[0008] Ward et al., in U.S. Pat No. 4,831,071, disclose a method
for improving the melt integrity and strength of a high modulus
thermoplastic resin to provide smooth-surfaced, high tolerance
profiles when the modified resin is melt-drawn. As in the case of
the disclosures to Arkles et al., cited supra, a silicone mixture
is cured via a hydrosilation reaction after being dispersed in the
resin to form a semi-IPN, after which the resulting composition is
extruded and melt-drawn.
[0009] U.S. Pat No. 6,013,715 to Gornowicz et al. teaches the
preparation of TPSiV elastomers wherein a silicone gum (or filled
silicone gum) is dispersed in either a polyolefin or a
poly(butylene terephthalate) resin and the gum is subsequently
dynamically vulcanized therein via a hydrosilation cure system. The
resulting elastomers exhibit an ultimate elongation at break of at
least 25% and have significantly improved mechanical properties
over the corresponding simple blends of resin and silicone gum in
which the gum is not cured (i.e., physical blends). This is, of
course, of great commercial significance since the vulcanization
procedure, and the cure agents required therefor, add to both the
complexity as well as the expense of the preparation and
vulcanization would be avoided in many applications if essentially
identical mechanical properties could be obtained without its
employ. However, this patent specifically teaches that
poly(ethylene terephthalate) resin, as well as other thermoplastic
resins, could not be modified according to the disclosed
method.
[0010] Although the above publications disclose the preparation of
compositions using various thermoplastic resins as the matrix and a
dispersed phase consisting of a silicone oil or elastomer which is
dynamically vulcanized therein, neither these references, nor any
art known to applicants, teach the preparation of TPSiV elastomers
based on polyester resins having superior tensile and elongation
properties, as disclosed herein.
SUMMARY OF THE INVENTION
[0011] It has now been discovered that TPSiV elastomers of the type
described in above cited U.S. Pat No. 6,013,715 can be prepared
from various polyester resins, including poly(ethylene
terephthalate). As in the case of the teachings of U.S. Pat. No.
6,013,715, the elastomers disclosed herein generally also have good
appearance and have a tensile strength and/or elongation at least
25% greater than that of the corresponding simple (physical) blend
wherein the diorganopolysiloxane is not cured. However, it has been
surprisingly found that such properties are significantly enhanced
when a minor portion of a stabilizer is incorporated in the
formulation, this resulting in a TPSiV having an elongation of at
least 30%. Furthermore, unlike the teachings of Arkles, cited
supra, and others, the silicone component which is dispersed in the
thermoplastic resin, and dynamically cured therein, must include a
high molecular weight gum, rather than a low viscosity silicone
fluid, the latter resulting in compositions having poor uniformity.
Surprisingly, polyesters having a softening point greater than
about 300.degree. C. could not be modified according to the present
invention to prepare TPSiVs having the required 30% elongation.
[0012] The present invention, therefore, relates to a method for
preparing a thermoplastic elastomer, said method comprising:
[0013] (I) mixing
[0014] (A) a thermoplastic resin comprising more than 50 percent by
volume of a polyester resin other than poly(butylene
terephthalate), said thermoplastic resin having a softening point
of 23.degree. C. to 300.degree. C.,
[0015] (B) a silicone elastomer comprising
[0016] (B') 100 parts by weight of a diorganopolysiloxane gum
having a plasticity of at least 30 and having an average of at
least 2 alkenyl groups in its molecule and, optionally,
[0017] (B") up to 200 parts by weight of a reinforcing filler, the
weight ratio of said silicone elastomer (B) to said thermoplastic
resin (A) being greater than 35:65 to 85:15,
[0018] (C) 0.01 to 5 parts by weight of a stabilizer for each 100
parts by weight of said thermoplastic resin and said silicone
elastomer,
[0019] (D) an organohydrido silicon compound which contains an
average of al. least 2 silicon-bonded hydrogen groups in its
molecule and
[0020] (E) a hydrosilation catalyst, components (D) and (E) being
present in an amount sufficient to cure said diorganopolysiloxane
(B'); and
[0021] (II) dynamically curing said diorganopolysiloxane (B'),
[0022] wherein said thermoplastic elastomer has an elongation of at
least 30% and
[0023] wherein at least one property of the thermoplastic elastomer
selected from tensile strength or elongation is at least 25%
greater than the respective property for a corresponding simple
blend wherein said diorganopolysiloxane is not cured.
[0024] The invention further relates to a thermoplastic elastomer
which is prepared by the above method.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Component (A) of the present invention is (A') a saturated
thermoplastic polyester resin, other than poly(butylene
terephthalate), or a blend of at least one such polyester resin
with (A") a non-polyester, saturated thermoplastic resin, wherein
the polyester resin (A') comprises more than 50 percent of the
blend volume. For the purposes of the invention, the polyester
resin (A') and the optional thermoplastic resin (A") have a
softening point of at least about 23.degree. C. but no greater than
about 300.degree. C. Herein, the "softening point" corresponds to
the respective melting point of the thermoplastic resin if this
resin (or blend) is at least partially crystalline and corresponds
to the glass transition temperature when the thermoplastic resin is
completely amorphous. When the softening point is below about
23.degree. C., the resin is not a thermoplastic. Rather, such a
material would already have an elastomeric character and
modification thereof according to the method of the present
invention would not be productive. On the other hand, a polyester
resin, or resin blend, having a softening point greater than about
300.degree. C. can not be formulated into thermoplastic elastomers
by the instant method. Preferably, the softening point is between
50.degree. C. and 300.degree. C. and most preferably between
200.degree. C. and 300.degree. C. Further, as used herein, the term
"saturated thermoplastic" indicates that the resin does not contain
aliphatic unsaturation.
[0026] Specific examples of resins which can comprise the saturated
thermoplastic polyester of component (A') include homopolymers such
as poly(ethylene terephthalate) (PET), poly(trimethylene
terephthalate) (PTT), poly(ethylene naphthalate) (PEN),
poly(butylene naphthalate) (PBN), and poly(cyclohexylenedimethylene
terephthalate) (PCT), inter alia. Alternatively, the polyester (A')
can be a random, graft or block copolymer having more than 50 mole
percent of its repeat units derived from the condensation of an
organic diacid and an organic diol. Such copolymers can comprise
(a) recurring structural units, wherein each structural unit
comprises a diol residue and a diacid residue and wherein from 50
to 100 mol percent of the structural units comprise a divalent
alicyclic hydrocarbon group as the diol residue of the structural
unit (e.g., PCT and glycol modified polycyclohexyl terephthalate
(PCT-G)); (b) recurring structural units, wherein each structural
unit comprises a diol residue and a diacid residue and from 0 to
less than 50% of the structural units comprise a divalent alicyclic
hydrocarbon radical as the diol residue of the structural unit
(e.g., PET-G); and (c) recurring structural units, wherein each
structural unit comprises a diol residue and a diacid residue and
wherein from 10 to less than 90% of the structural units comprise a
divalent alicyclic hydrocarbon radical as the 3diol residue of the
structural unit and from 10 to 90% of the structural units comprise
a 2,6-naphythalene dicarboxylate group as the diacid residue of the
structural unit. When the polyester resin contains two or more
blocks having independent thermal transition temperatures, the
above mentioned softening point refers to the higher melt point or
glass transition temperature.
[0027] Saturated thermoplastic polyester resins are well known in
the art and further description thereof is considered
unnecessary.
[0028] It is preferred that the polyester resin is dried prior to
use, as generally recommended by the manufacturer. This is
typically accomplished by passing a dry air or inert gas stream
over as-received resin pellets or powder at elevated temperatures.
The degree of drying consistent with optimal ultimate elastomer
properties depends on the particular polyester and other components
of the invention and is readily determined by a few simple
experiments for the system under consideration.
[0029] Optional thermoplastic resin (A") is any saturated resin
other than a polyester having a softening point of 23.degree. C. to
300.degree. C. The nature of this component is not critical
provided it does not contain functional groups which would prevent
the dynamic vulcanization of the silicone gum (B"). It may be
illustrated by thermoplastic resins such as polycarbonates (PC),
acrylonitrile-butadiene-styrene terpolymers (ABS), polyamides,
polystyrene, poly(phenylene oxide) (PPO), polypropylene (PP),
thermoplastic polyolefins (TPO), polyetherimide (PEI) and
polyketones, inter alia.
[0030] Silicone elastomer (B) is a diorganopolysiloxane gum (B')
or, optionally, a uniform blend of this gum with a reinforcing
filler (B").
[0031] Diorganopolysiloxane (B') is a high consistency (gum)
polymer or copolymer which contains at least 2 alkenyl groups
having 2 to 20 carbon atoms in its molecule. The alkenyl group is
specifically exemplified by vinyl, allyl, butenyl, pentenyl,
hexenyl and decenyl. The position of the alkenyl functionality is
not critical and it may be bonded at the molecular chain terminals,
in non-terminal positions on the molecular chain or at both
positions. It is preferred that the alkenyl group is vinyl or
hexenyl and that this group is present at a level of 0.001 to 3
weight percent, preferably 0.01 to 1 weight percent, in the
diorganopolysiloxane gum.
[0032] The remaining (i.e., non-alkenyl) silicon-bonded organic
groups in component (B') are independently selected from
hydrocarbon or halogenated hydrocarbon groups which contain no
aliphatic unsaturation. These may be specifically exemplified by
alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl,
propyl, butyl, pentyl and hexyl; cycloalkyl groups, such as
cyclohexyl and cycloheptyl; aryl groups having 6 to 12 carbon
atoms, such as phenyl, tolyl and xylyl; aralkyl groups having 7 to
20 carbon atoms, such as benzyl and phenethyl; and halogenated
alkyl groups having 1 to 20 carbon atoms, such as
3,3,3-trifluoropropyl and chloromethyl. It will be understood, or
course, that these groups are selected such that the
diorganopolysiloxane gum (B') has a glass temperature (or melt
point) which is below room temperature and the gum is therefore
elastomeric. Methyl preferably makes up at least 50, more
preferably at least 90, mole percent of the non-alkenyl
silicon-bonded organic groups in component (B').
[0033] Thus, diorganopolysiloxane (B') can be a homopolymer or a
copolymer containing such organic groups. Examples include gums
comprising dimethylsiloxy units and phenylmethylsiloxy units;
dimethylsiloxy units and diphenylsiloxy units; and dimethylsiloxy
units, diphenylsiloxy units and phenylmethylsiloxy units, among
others. The molecular structure is also not critical and is
exemplified by linear and partially branched straight-chain, linear
structures being preferred.
[0034] Specific illustrations of organopolysiloxane (B') include:
trimethylsiloxy-endblocked dimethylsiloxane-methylhexenylsiloxane
copolymers; dimethylhexenylsiloxy-endblocked
dimethylsiloxane-methylhexen- ylsiloxane copolymers;
trimethylsiloxy-endblocked dimethylsiloxane-methylv- inylsiloxane
copolymers; trimethylsiloxy-endblocked
methylphenylsiloxane-dimethylsiloxane-methylvinylsiloxane
copolymers; dimethylvinylsiloxy-endblocked dimethylpolysiloxanes;
dimethylvinylsiloxy-endblocked dimethylsiloxane-methylvinylsiloxane
copolymers; dimethylvinylsiloxy-endblocked
methylphenylpolysiloxanes; dimethylvinylsiloxy-endblocked
methylphenylsiloxane-dimethylsiloxane-meth- ylvinylsiloxane
copolymers; and similar copolymers wherein at least one end group
is dimethylhydroxysiloxy. Preferred systems for low temperature
applications include
methylphenylsiloxane-dimethylsiloxane-methylvinylsil- oxane
copolymers and
diphenylsiloxane-dimethylsiloxane-methylvinylsiloxane copolymers,
particularly wherein the molar content of the dimethylsiloxane
units is about 93%.
[0035] Component (B') may also include combinations of two or more
organopolysiloxanes. Most preferably, component (B') is a
polydimethylsiloxane homopolymer which is terminated with a vinyl
group at each end of its molecule or is such a homopolymer which
also contains at least one vinyl group along its main chain.
[0036] For the purposes of the present invention, the molecular
weight of the diorganopolysiloxane gum is sufficient to impart a
Williams plasticity number of at least about 30 as determined by
the American Society for Testing and Materials (ASTM) test method
926. The plasticity number, as used herein, is defined as the
thickness in millimeters .times.100 of a cylindrical test specimen
2 cm.sup.3 in volume and approximately 10 mm in height after the
specimen has been subjected to a compressive load of 49 Newtons for
three minutes at 25.degree. C. When the plasticity of this
component is less than about 30, as in the case of the low
viscosity fluid siloxanes employed by Arkles, cited supra, the
TPSiVs prepared by dynamic vulcanization according to the instant
method exhibit poor uniformity such that at high silicone contents
(e.g., 50 to 70 weight percent) there are regions of essentially
only silicone and those of essentially only thermoplastic resin,
and the compositions are weak and friable. These gums are
considerably more viscous than the silicone fluids employed in the
prior art. For example, silicones contemplated by Arkles, cited
supra, have an upper viscosity limit of 100,000 cS (0.1 m.sup.2/s)
and, although the plasticity of fluids of such low viscosity are
not readily measured by the ASTM D 926 procedure, it was determined
that this corresponds to a plasticity of approximately 24. Although
there is no absolute upper limit on the plasticity of component
(B'), practical considerations of processability in conventional
mixing equipment generally restrict this value. Preferably, the
plasticity number should be about 100 to 200, most preferably about
120to185.
[0037] Methods for preparing high consistency unsaturated
group-containing polydiorganosiloxanes are well known and they do
not require a detailed discussion in this specification. For
example, a typical method for preparing an alkenyl-functional
polymer comprises the base-catalyzed equilibration of cyclic and/or
linear diorganopolysiloxanes in the presence of similar
alkenyl-functional species.
[0038] Component (B") is a finely divided filler which is known to
reinforce diorganopolysiloxane (B') and is preferably selected from
finely divided, heat stable minerals such as fumed and precipitated
forms of silica, silica aerogels and titanium dioxide having a
specific surface area of at least about 50 m.sup.2/gram. The fumed
form of silica is a preferred reinforcing filler based on its high
surface area, which can be up to 450 m.sup.2/gram and a fumed
silica having a surface area of 50 to 400 m.sup.2/g, most
preferably 200 to 380 m.sup.2/g, is highly preferred. Preferably,
the fumed silica filler is treated to render its surface
hydrophobic, as typically practiced in the silicone rubber art.
This can be accomplished by reacting the silica with a liquid
organosilicon compound which contains silanol groups or
hydrolyzable precursors of silanol groups. Compounds that can be
used as filler treating agents, also referred to as anti-creeping
agents or plasticizers in the silicone rubber art, include such
ingredients as low molecular weight liquid hydroxy-or
alkoxy-terminated polydiorganosiloxanes, hexaorganodisiloxanes,
cyclodimethylsilazanes and hexaorganodisilazanes. It is preferred
that the treating compound is an oligomeric hydroxy-terminated
diorganopolysiloxane having an average degree of polymerization
(DP) of 2 to about 100, more preferably about 2 to about 10, and it
is used at a level of about 5 to 50 parts by weight for each 100
parts by weight of the silica filler. When component (B') is the
preferred vinyl-functional or hexenyl-functional
polydimethylsiloxane, this treating agent is preferably a
hydroxy-terminated polydimethylsiloxane.
[0039] When reinforcing filler (B") is employed, it is added at a
level of up to 200 parts by weight, preferably 5 to 150 and most
preferably 20 to 100 parts by weight, for each 100 parts by weight
of gum (B') to prepare silicone elastomer (B). Such a blend is
commonly termed a "base" by those skilled in the silicone art.
Blending is typically carried out at room temperature using a
two-roll mill, internal mixer or other suitable device.
Alternatively, a reinforcing filler-containing silicone elastomer
can be formed in-situ during mixing, but prior to dynamic
vulcanization of the gum, as further described infra. In the latter
case, the temperature of mixing is kept below the melting point of
the polyester resin until the reinforcing filler is well dispersed
in the diorganlopolysiloxane gum.
[0040] Stabilizer (C) is at least one organic compound selected
from hindered phenols; thioesters; hindered amines;
2,2'-(1,4-phenylene)bis(4H- -3, 1-benzoxazin-4-one); or
3,5-di-tert-butyl-4-hydroxybenzoic acid, hexadecyl ester. We have
surprisingly observed that other classes of stabilizers recommended
for formulating polyester compositions, such as organophosphites,
do not impart the significant improvement in mechanical properties
obtained with the stabilizers of the invention. Moreover, as shown
in the examples below, some of the organophosphites actually
contribute to the premature crosslinking of the silicone gum (i.e.,
before any catalyst is introduced), thereby interfering with the
intended dynamic vulcanization.
[0041] For the purposes of the present invention, a hindered phenol
is an organic compound having at least one group of the formula
1
[0042] in its molecule, wherein Q is a monovalent organic group
having 1 to 24 carbon atoms selected from hydrocarbon groups,
hydrocarbon groups which optionally contain heteroatoms selected
from sulfur, nitrogen or oxygen or halogen-substituted versions of
the aforementioned groups. Examples of Q include groups such as
alkyl, aryl, alkylaryl, arylalkyl, cycloalkyl and
halogen-substituted version thereof, alkoxy groups having 1 to 24
carbon atoms, such as methoxy or t-butoxy; and hydrocarbon groups
having 2 to 24 carbon atoms which contain heteroatoms (e.g.,
--CH.sub.2--S--R", --CH.sub.2--O--R" or --CH.sub.2--C(O)OR",
wherein R" is a hydrocarbon group having 1 to 18 carbon atoms).
Further, although not explicitly shown in formula (i), it is also
contemplated that the benzene ring may additionally be substituted
with one or more of the above described Q groups. The residue of
the organic compound to which group (i) is chemically bonded is not
critical as long as it does not contain moieties which would
interfere with the dynamic vulcanization, described infra. For
example, this residue may be a hydrocarbon, a substituted
hydrocarbon or a hetero atom-containing hydrocarbon group of the
appropriate valence. It is also contemplated that the group
according to formula (i) can be attached to hydrogen to form an
organophenol. Preferably, the hindered phenol compound has a number
average molecular weight of less than about 3,000.
[0043] A preferred hindered phenol compound contains at least one
group of the formula 2
[0044] in its molecule wherein the benzene ring may be optionally
further substituted with hydrocarbon groups having 1 to 24 carbon
atoms. In formula (ii), R is am alkyl group having one to four
carbon atoms and R' is a hydrocarbon group having 4 to 8 carbon
atoms.
[0045] Preferably, one to four of the groups shown in structures
(i) or (ii) are attached to an organic residue of appropriate
valence such that the contemplated compound has a molecular weight
(MW) of less than about 1,500. Most preferably, four such groups
are present in component (C) and this compound has a molecular
weight of less than about 1,200. This monovalent (or polyvalent)
organic residue can contain one or more heteroatoms such as oxygen,
nitrogen, phosphorous and sulfur. The R' groups in the above
formula may be illustrated by t-butyl, n-pentyl, butenyl, hexenyl,
cyclopentyl, cyclohexyl and phenyl. It is preferred that both R and
R' are t-butyl. For the purposes of the present invention, a group
according to formula (ii) can also be attached to hydrogen to form
a diorganophenol.
[0046] Non-limiting specific examples of suitable hindered phenols
include 1,1,3-Tris(2'-methyl-4'-hydroxy-5'-t-butylphenyl)butane,
N,N'-hexamethylene
bis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide),
4,4'-thiobis(2-t-butyl-5-methylphenol),
1,3,5-tris(4-tert-butyl-3-hydroxy- -2,6-dimethyl
benzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione,
N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamamide),
tetrakis(methylene(3,5-di-tert-butyl-4-hydroxy-hydrocinnamate))methane,
1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl)
benzene, 4,4'-methylenebis (2,6-di-tertiary-butylphenol),
2,2'-thiobis(6-tert-buty- l-4-methylphenol),
2,2'-thiobis(4-octylphenol), 4,4'-thiobis(6-tert-butyl--
2-methylphenol), 4,4'-thiobis(3,6-di-sec-amylphenol),
2-(4,6-bis(2,4-dimethylphenyl)-1,3,5,-triazin-2-yl)-5-(octyloxy)
phenol,
2,4-bisoctylmercapto-6-(3,5-di-tert-butyl-4-hydroxyanilino)-1,3,5-triazin-
e, 2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenoxy)-1,2,3-triazine,
1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate,
2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4-hydroxyanilino)-1,3,5-triazin-
e,
2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4-hydroxyphenoxy)-1,3,5-triaz-
ine,
2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenylethyl)-1,3,5-triazine,
1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hexahydro-1,3,5-tri-
azine, 1,3,5-tris(3,5-dicyclohexyl-4-hydroxybenzyl) isocyanurate,
1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate,
2,6-di-tert-butyl-4-methoxyphenol, 2,5-di-tert-butylhydroquinone,
2,5-di-tert-amylhydroquinone, 2,6-di-tert-butylhydroquinone,
2,5-di-tert-butyl-4-hydroxyanisole,
2,6-diphenyl-4-octadecyloxyphenol,
3,5-di-tert-butyl-4-hydroxyanisole,
3,5-di-tert-butyl-4-hydroxyphenyl stearate,
bis(3,5-di-tert-butyl-4-hydroxyphenyl) adipate, esters of
beta-(3,5-di-tert-butyl-4-hydroxyphenl)propionic acid with mono- or
polyhydric alcohols (e.g., methanol, ethanol, n-octanol,
trimethylhexanediol, isooctanol, octadecanol, 1,6-hexanediol,
1,9-nonamediol, ethylene glycol, 1,2-propanediol, neopentyl glycol,
thiodiethylene glycol, diethylene glycol, triethylene glycol,
pentaerythritol, trimethylolpropane, tris(hydroxyethyl)
isocyanurate, N,N'-bis(hydroxyethyl)oxalamide, 3-thiaundecanol,
3-thiapentadecanol,
4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo(2.2.2) octane and
esters of beta-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionic
acid with mono- or polyhydric alcohols (as above).
[0047] Thioesters of the invention are compounds having at least
one group of the formula
G-S-G (iii)
[0048] wherein G is --CH.sub.2--CH.sub.2--C(O)OR'"
[0049] and R'" is a monovalent hydrocarbon group having 1 to 24
carbon atoms. Specific non-limiting examples of suitable thioesters
include distearyl 3,3'-thiodipropionate,
dilauryl-3,3'-thiodipropionate and
di(tridecyl)3,3'-thiodipropionate.
[0050] The hindered amine of the present invention is a low
molecular weight organic compound or a polymer which contains at
least one divalent group of the formula 3
[0051] wherein Me hereinafter denotes a methyl group. The backbone
of this component is not critical as long as it does not contain
functionality which would interfere with the dynamic vulcanization
of the silicone gum and it may be illustrated by low-molecular and
polymeric polyalkylpiperidines, as disclosed in U.S. Pat No.
4,692,486, hereby incorporated by reference. Preferably, the above
group has the structure 4
[0052] wherein Z is selected from hydrogen or an alkyl group having
1 to 24 carbon atoms, preferably hydrogen.
[0053] Specific non-limiting examples of suitable hindered amines
include: 1,6-hexanediamine,
N,N'-bis(2,2,6,6-pentamethyl-4-piperidinyl)-, polymers with
morpholine-2,4,6-trichloro-1,3,5-triazine; 1,6-hexanediamine,
N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-, polymers with
2,4,-Dichloro-6-(4-morpholinyl)-1,3,5-triazine;
bis(1,2,2,6,6-pentamethyl- -4-piperidinyl) sebacate;
bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate; dimethyl succinate
polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidin- e ethanol;
and polymethyl (propyl-3-oxy-(2',2',6',6'-tetramethyl-4'-piperi-
dinyl) siloxane.
[0054] Preferred stabilizers of the invention are
tetrakis(methylene(3,5-d-
i-tert-butyl-4-hydroxy-hydrocinnamate))methane,
N,N'-hexamethylenebis(3,5--
di-tert-lutyl-4-hydroxyhydrocinnamamide) and
1,1,3-tris(2'-methyl-4'-hydro- xy-5'-t-butylphenyl)butane.
[0055] From about 0.01 to about 5 parts by weight of stabilizer (C)
are employed for each 100 parts by weight of resin (A) plus
silicone elastomer (B). It has been found that the mechanical
properties of the final thermoplastic elastomer are significantly
diminished when less than about 0.01 part of component (C) is used.
This is particularly true when the polyester has a relatively high
melting point, such as is the case for PEN and PCT resins. On the
other hand, when the content of component (C) is greater than about
5 weight parts for each 100 parts by weight of (A) plus (B), little
additional benefit is imparted. We have found that, in general,
more stabilizer is required as the softening point of the resin
approaches the 300.degree. C. limit. With this guidance, the
skilled artisan will readily determine the appropriate amount of
stabilizer for any given system by routine experimentation.
Preferably, 0.1 to 2 parts by weight, more preferably 0.1 to 1 part
by weight, of (C) are added for each 100 parts by weight of (A)
plus (B).
[0056] The organohydrido silicon compound (D) is a crosslinker
(cure agent) for diorganopolysiloxane (B') of present composition
and is an organopolysiloxane which contains at least 2
silicon-bonded hydrogen atoms in each molecule, but having at least
about 0.1 weight percent hydrogen, preferably 0.2 to 2 and most
preferably 0.5 to 1.7, percent hydrogen bonded to silicon. Those
skilled in the art will, of course, appreciate that either
component (B') or component (D), or both, must have a functionality
greater than 2 if diorganopolysiloxane (B') is to be cured (i.e.,
the sum of these functionalities must be greater than 4 on
average). The position of the silicon-bonded hydrogen i a component
(D) is not critical, and it may be bonded at the molecular chain
terminals, in non-terminal positions along the molecular chain or
at both positions. The silicon-bonded organic groups of component
(D) are independently selected from any of the hydrocarbon or
halogenated hydrocarbon groups described above in connection with
diorganopolysiloKane (B'), including preferred embodiments thereof.
The molecular structure of component (D) is also not critical and
is exemplified by straight-chain, partially branched
straight-chain, branched, cyclic and network structures, linear
polymers or copolymers being preferred.
[0057] Component (D) is exemplified by the following:
[0058] low molecular siloxanes, such as
PhSi(OSiMe.sub.2H).sub.3;
[0059] trimethylsiloxy-endblocked methylhydridopolysiloxanes;
[0060] trimethylsiloxy-endblocked
dimethylsiloxane-methylhydridosiloxane copolymers;
[0061] dimethylhydridosiloxy-endblocked dimethylpolysiloxanes;
[0062] dimethylhydrogensiloxy-endblocked
methylhydrogenpolysiloxanes;
[0063] dimethylhydridosiloxy-endblocked
dimethylsiloxane-methylhydridosilo- xane copolymers;
[0064] cyclic methylhydrogenpolysiloxanes;
[0065] cyclic dimethylsiloxane-methylhydridosiloxane
copolymers;
[0066] tetrakis(dimethylhydrogensiloxy)silane;
[0067] silicone resins composed of (CH.sub.3).sub.2HSiO.sub.1/2,
(CH.sub.3).sub.3SiO.sub.1/2, and SiO.sub.4/2 units; and
[0068] silicone resins composed of (CH.sub.3).sub.2HSiO.sub.1/2,
(CH.sub.3).sub.3SiO.sub.1/2,
[0069] CH.sub.3Si O.sub.3/2, PhSiO.sub.3/2 and SiO.sub.4/2
units,
[0070] wherein Ph hereinafter denotes phenyl group.
[0071] Particularly preferred organohydrido silicon compounds are
polymers or copolymers with R"" HSiO units ended with either
R"".sub.3SiO.sub.1/2 or HR"".sub.2SiO.sub.1/2, wherein R"" is
independently selected from alkyl groups having 1 to 20 carbon
atoms, phenyl or trifluoropropyl, preferably methyl. It is also
preferred that the viscosity of component (D) is about 0.5 to 1,000
mPa-s at 25.degree. C., preferably 2 to 500 mPa-s. Further, this
component preferably has 0.5 to 1.7 weight percent hydrogen bonded
to silicon. It is highly preferred that component (D) is selected
from a polymer consisting essentially of methylhydridosiloxane
units or a copolymer consisting essentially of dimethylsiloxane
units and methylhydridosiloxane units, having 0.5 to 1.7 percent
hydrogen bonded to silicon and having a viscosity of 2 to 500 mPa-s
at 25.degree. C. Such a highly preferred system has terminal groups
selected from trimethylsiloxy or dimethylhdridosiloxy groups. These
SiH-functional materials are well known in the art and many of them
are commercially available.
[0072] Component (D) may also be a combination of two or more of
the above described systems and is used at a level such that the
molar ratio of SiH therein to Si-alkenyl in component (B') is
greater than 1 and preferably below about 50, more preferably 3 to
30, most preferably 4 to 20.
[0073] Hydrosilation catalyst (E) accelerates the cure of
diorganopolysiloxane (B') in the present composition. This
hydrosilation catalyst is exemplified by platinum catalysts, such
as platinum black, platinum supported on silica, platinum supported
on carbon, chloroplatinic acid, alcohol solutions of chloroplatinic
acid, platinum/olefin complexes, platinum/alkenylsiloxane
complexes, platinum/beta-diketone complexes, platinum/phosphine
complexes and the like; rhodium catalysts, such as rhodium chloride
and rhodium chloride/di(n-butyl)sulfide complex and the like; and
palladium catalysts, such as palladium on carbon, palladium
chloride and the like. Component (E) is preferably a platinum-based
catalyst such as chloroplatinic acid; platinum dichloride; platinum
tetrachloride; a platinum complex catalyst produced by reacting
chloroplatinic acid and divinyltetramethyldisiloxane which is
diluted with dimethylvinylsiloxy endblocked polydimethylsiloxane,
prepared according to U.S. Pat. No. 3,419,593 to Willing; and a
neutralized complex of platinous chloride and
divinyltetramethyldisiloxarne, prepared according to U.S. Pat. No.
5,175,325 to Brown et al. Most preferably, catalyst (E) is a
neutralized complex of platinous chloride and
divinyltetramethyldisiloxane.
[0074] Component (E) is added to the present composition in a
catalytic quantity sufficient to promote the reaction of components
(B') and (D) and thereby cure the diorganopolysiloxane to form an
elastomer. The catalyst is typically added so as to provide about
0.1 to 500 parts per million (ppm) of metal atoms based on the
total weight of the thermoplastic elastomer composition, preferably
0.25 to 100 ppm.
[0075] In addition to the above-mentioned components (A) through
(E), a minor amount (i.e., less than about 40 weight percent of the
total composition, preferably less than 20 weight percent) of an
optional additive (F) can be incorporated in the compositions of
the present invention. This optional additive can be illustrated
by, but are not limited to, fillers, such as glass fibers and
carbon fibers, quartz, talc, calcium carbonate, diatomaceous earth,
iron oxide, carbon black and finely divided metals; lubricants;
plasticizers; pigments; dyes; anti-static agents; blowing agents;
heat stabilizers, such as hydrated cerric oxide; antioxidants; and
fire retardant (FR) additives, such as halogenated hydrocarbons,
alumina trihydrate, magnesium hydroxide and organophosphorous
compounds. A preferred FR additive is calcium silicate particulate,
preferably wollastonite having an average particle size of 2 to 30
.mu.m. The FR additive can be incorporated in the silicone gum (B')
or in resin (A), or in both.
[0076] The above additives are typically added to the final
thermoplastic composition after dynamic cure, but they may also be
added at any point in the preparation provided they do not
adversely affect dynamic vulcanization. Of course, the above
additional ingredients are only used at levels which do not
significantly detract from the desired properties of the final
composition.
[0077] According to the method of the present invention, the
thermoplastic elastomer is prepared by thoroughly mixing silicone
elastomer (B) and stabilizer (C) with resin (A) and then
dynamically vulcanizing the diorganopolysiloxane using
organohydrido silicon compound (D)) and catalyst (E). For the
purposes of the present invention, the weight ratio of silicone
elastomer (B) to resin (A) is greater than 35:65. It has been found
that when this ratio is 35:65 or less, the resulting vulcanizate
has a modulus more resembling that of thermoplastic resin (A) than
that of a thermoplastic elastomer. On the other hand, the above
mentioned ratio should be no more than 85:15 since the compositions
tend to be weak and resemble cured silicone elastomers above this
value. Notwithstanding this upper limit, the maximum weight ratio
of (B) to (A) for any given combination of components is also
limited by processability considerations since too high a silicone
elastomer content results in at least a partially crosslinked
continuous phase which is no longer thermoplastic. For the purposes
of the present invention, this practical limit is readily
determined by routine experimentation and represents the highest
level of component (B) which allows the TPSiV to be compression
molded. It is, however, preferred that the final thermoplastic
elastomer can also be readily processed in other conventional
plastic operations, such as injection molding and extrusion and, in
this case, the weight ratio of components (B) to (A) should be no
more than about 75:25. Such a preferred thermoplastic elastomer
which is subsequently re-processed generally has a tensile strength
and elongation similar to the corresponding values for the original
TPSiV (i.e., the thermoplastic elastomer is little changed by this
re-processing). Although the amount of silicone elastomer
consistent with the above mentioned requirements depends upon the
particular polyester resin and other components selected, it is
preferred that the weight ratio of components (B) to (A) is 40:60
to 75:25, more preferably 40:60 to 70:30.
[0078] Mixing is carried out in any device which is capable of
uniformly dispersing the components in the polyester resin or resin
blend, such as an internal mixer or an extruder, the latter being
preferred for commercial preparations, wherein the temperature is
preferably kept as low as practical consistent with good mixing so
as not. to degrade the resin. Depending upon the particular system,
order of mixing is generally not critical and, for example,
components (A), (C) and (D) can be added to (B) at a temperature
above the softening point of (A), catalyst (E) then being
introduced to initiate dynamic vulcanization. However, components
(B) through (D) should be well dispersed in resin (A) before
dynamic vulcanization begins. As previously mentioned, it is also
contemplated that a reinforcing filler-containing silicone
elastomer can be formed in-situ. For example, the optional
reinforcing filler may be added to a mixer already containing resin
(A) and diorganopolysiloxane gum (B') at a temperature below the
softening point of the resin to thoroughly disperse the filler in
the gum. The temperature is then raised to melt the resin, the
other ingredients are added and mixing/dynamic vulcanization are
carried out. Optimum temperatures, mixing times and other
conditions of the mixing operation depend upon the particular resin
and other components under consideration and these may be
determined by routine experimentation by those skilled in the art.
It is, however, preferred to carry out the mixing and dynamic
vulcanization under a dry, inert atmosphere (i.e., one that does
not adversely react with the components or otherwise hider
hydrosilation cure), such as dry nitrogen, helium or argon.
[0079] A preferred procedure according to the instant method
comprises forming a pre-mix by blending dried polyester resin (A),
silicone elastomer (B), stabilizer (IC) and, optionally,
organohydrido silicon compound (D) below the softening point of the
resin (e.g., at ambient conditions). This pre-mix is then melted in
a bowl mixer or internal mixer, preferably using a dry inert gas
purge, at a controlled temperature which is just above the
softening of the resin to about 35.degree. C. above this value and
catalyst (E) is mixed therewith. Mixing is continued until the melt
viscosity (mixing torque) reaches a steady state value, thereby
indicating that dynamic vulcanization of the diorganopolysiloxane
of component (B) is complete. Such a "cold-blend" procedure is
particularly preferred when the melt point of the polyester resin
is above about 280.degree. C., as in the case of, e.g., PCT
resin.
[0080] As noted above, in order to be within the scope of the
present invention, the tensile strength or elongation, or both, of
the TPSiVs must be at least 25% greater than that of a
corresponding simple blend. A further requirement of the invention
is that the TPSiV has at least 30% elongation, as determined by the
test described infra. In this context, the term "simple blend" or
"physical blend" denotes a composition wherein the weight
proportions of resin (A), elastomer (B) and stabilizer (C) are
identical to the proportions in the TPSiV, but no cure agents are
employed (i.e., either component (D) or (E), or both, are omitted
and the gum is therefore not cured). In order to determine if a
particular composition meets the above criterion, the tensile
strength of the TPSiV is measured on dumbbells having a length of
25.4 mm and a width of 3.2 mm and a typical thickness of 1 to 2 mm,
according to ASTM method D 412, at an extension rate of 50 mm/min.
Five samples are evaluated and the results averaged after removing
obvious low readings due to sample inhomogeneity (e.g., such as
voids, contamination or inclusions). These values are then compared
to the corresponding average tensile and elongation values of a
sample prepared from the simple blend composition. When at least a
25% improvement in tensile and/or elongation over the simple blend
is not realized there is no benefit derived from the dynamic
vulcanization and such compositions are not within the scope of the
present invention.
[0081] The thermoplastic elastomer prepared by the above-described
method can then be processed by conventional techniques, such as
extrusion, vacuum forming, injection molding, blow molding or
compression molding. Moreover, these compositions can be
re-processed (recycled) with little or no degradation of mechanical
properties.
[0082] The novel thermoplastic elastomers of the present invention
can be used for fabricating parts and components for automotive,
electronics, electrical, communications, appliance and medical
applications, inter alia. For example, they may be used to produce
wire and cable insulation; automotive and appliance components,
such as belts, hoses, boots, bellows, gaskets, fuel line components
and air ducts; architectural seals; bottle closures; furniture
components; soft-feel grips for hand held devices (e.g. handles for
tools); medical devices; sporting goods and general rubber
parts.
EXAMPLES
[0083] The following examples are presented to further illustrate
the compositions and method of this invention, but are not to be
construed as limiting the invention, which is delineated in the
appended claims. All parts and percentages in the examples are on a
weight basis and all measurements were obtained at about 23.degree.
C., unless indicated to the contrary.
[0084] Materials
[0085] The following materials, listed alphabetically for ease of
reference, were employed in the examples.
[0086] BASE 1 is a silicone rubber base made from 68.78% PDMS 1,
defined infra, 25.8% of a fumed silica having a surface area of
about 250 m.sup.2/g (Cab-O-Sil.RTM. MS-75 by Cabot Corp., Tuscola,
Ill.), 5.4% of a hydroxy-terminated diorganopolysiloxanc having an
average degree of polymerization (DP) of about 8 and 0.02% of
ammonia.
[0087] BASE 2 is a silicone rubber base made from 76.68% PDMS 1,
defined infra, 17.6% of a fumed silica having a surface area of
about 250 m.sup.2/g, 5.7% of a hydroxy-terminated
diorganopolysiloxane having an average degree of polymerization
(DP) of about 8 and 0.02% ammonium.
[0088] CATALYST 1 is a solution of one part of (i) a catalyst
composition consisting essentially of 1.5% of a platinum complex of
1,3-diethenyl-1,1,3,3-tetramethyldisiloxane, 6.0%
tetramethyldivinyldisil- oxane, 92% of a dimethylvinyl ended
polydimethylsiloxane and 0.5% of a dimethylcyclopolysiloxanes
having 6 or greater dimethylsiloxane units diluted in four parts of
(ii) a trimethylsiloxy-terminated polydimethylsiloxane oil having a
viscosity of 1,000 cSt (1,000 m.sup.2/s).
[0089] CATALYST 2 is the catalyst composition of CATALYST 1 which
was not diluted with the polydimethylsiloxane oil.
[0090] IRGAFOS.TM. 168 is a phosphite stabilizer marketed by Ciba
Specialty Chemicals Corporation and described as
tris(2,4-di-tert-butylph- enyl)phosphite.
[0091] IRGANOX.TM. 1010 is a hindered phenol stabilizer marketed by
Ciba Specialty Chemicals Corporation and described as
tetrakis(methylene(3,5-d-
i-tert-butyl-4-hydroxy-hydrocinnamate))methane.
[0092] LCP is a liquid crystalline polyester resin marketed as
VECTRA.TM. E950i by Ticona. Melt point=336.degree. C.
[0093] PCT is a poly(cyclohexylenedimethylene terephthalate)
marketed as THERMX.RTM. 13787 by Eastman Chemical Co., Kingsport,
Tenn. Melt point=291.degree. C.
[0094] PDMS 1 is a gum consisting of 99.81 wt % Me.sub.2SiO units,
0.16% MeViSiO units and 0.03% Me.sub.2ViSiO.sub.1/2 units, wherein
Vi hereinafter represents a vinyl group. Prepared by potassium
catalyzed equilibration of cyclic siloxanes wherein the catalyst is
neutralized with carbon dioxide. This gum has plasticity of about
150.
[0095] PDMS 2 is a gum similar to PDMS 1 but neutralized with both
carbon dioxide and a silyl phosphate and having a plasticity of
about 150.
[0096] PEN is a poly(ethylene naphthalate) marketed as Hipertuf.TM.
40043 by Shell Chemical Company, Akron, Ohio. Melt
point=271.degree. C.
[0097] PET 1 is a poly(ethylene terephthalate), marketed as
Eastapac.TM. 7352 by Eastman Chemical Comp., Kingsport, Tenn. Melt
points=240.5.degree. C. and 252.degree. C.
[0098] PET 2 is a poly(ethylene terephthalate), marketed as
Eastapac.TM. 9663 by Eastman Chemical Comp. Melt point=245.degree.
C.
[0099] PET 3 is a poly(ethylene terephthalate), marketed as
Eastapac.TM. 9921 by Eastman Chemical Comp. Melt point=2350C.
[0100] PET 4 is a poly(ethylene terephthalate), marketed as
Arnite.TM. A04 102 by DSM Engineering Plastics, Evansville, Ind.
Melt points=244 and 253 .degree. C.
[0101] PET 5 is a poly(ethylene terephthalate), marketed as
Arnite.TM. D04 300 by DSM Engineering Plastics. Melt
point=244.degree. C.
[0102] PTT is a poly(trimethylene terephthalate), marketed as
Corterra.RTM. CP 509200 by Shell Chemical Company, Houston, Tex.
Melt point=228.degree. C.
[0103] WESTON.TM. W618G is a distearyl pentaerythritol diphosphite
stabilizer marketed by GE Specialty Chemicals, Morgantown,
W.Va.
[0104] X-LINKER 1 is an SiH-functional crosslinker consisting
essentially of 68.4% MeHSiO units, 28.1% Me.sub.2SiO units and 3.5%
Me.sub.3SiO.sub.1/2 units and has a viscosity of approximately 29
mpa.cndot.s. This corresponds to the average formula
MD.sub.16D'.sub.39M, in which M is (CH.sub.3).sub.3Si--O--, D is
--Si(CH.sub.3).sub.2--O-- and D' is 'Si(H)(CH.sub.3)'O'.
[0105] In some of the following examples, mixing of components was
started at a mixer temperature which was slightly below the melt
point of the polyester resin employed in order to avoid degradation
thereof as the actual temperature increased due to heat generated
by the mixing process. In each case, the actual temperature of the
mixed composition upon completion of vulcanization was above the
resin melt point.
[0106] (Comparative) Example A1
[0107] A physical blend was prepared by first drying PET 1 resin at
150.degree. C. for 5 hours. (analysis confirmed moisture content of
0.001%). One hundred and twenty grams of BASE 1 were mixed at 100
rpm in a Haake Polylab.TM. bowl mixer (310 ml bowl; roller blades)
at a temperature setting of 250.degree. C., and after 4 minutes,
80.0 g of the dried PET 1 resin were added. The mixing torque
increased to 1,500 m-g after a total time of 6 minutes. Torque
remained constant during the final 13 minutes of processing, at
which point a uniform blend was obtained (material
temperature=264.degree. C.; total time of mixing=19 minutes).
[0108] The above material was compression molded at 270.degree. C.
for 4 minutes under approximately 10 ton pressure (99 KPa) in a
stainless steel Endura.TM. 310-2 Coated mold followed by cold
pressing for 4 minutes. The tensile properties were measured on
dumbbells having a length of 25.4 mm, width of 3.18 mm and a
thickness of 1 to 2 mm, according to ASTM method D 412 at
23.degree. C. and an extension rate of 50 mm/min. Five samples were
tested, the results being averaged and presented in Table 1.
[0109] (Comparative) Example A2
[0110] The procedure of Comparative Example A1 was repeated wherein
0.15 g of IRGANOX.TM. 1010 was added to the PET 1/BASE 1 blend
after a mixing time of 8.5 minutes (torque=1,400 m-g). The torque
decreased over the next 10.5 minutes to a level of 1,200 m-g.
(material temperature=263.degree. C.). The resulting physical blend
was molded and tested as in Comparative Example A1 and results are
presented in Table A1.
[0111] (Comparative) Example A3
[0112] The procedure of Comparative Example A2 was repeated wherein
2.29 g of X-LINKER 1 were added to the PET 1/BASE 1/IRGANOX.TM.
1010 blend at approximately 12 minutes into the run. A torque of
1,100 m-g was recorded just after adding the crosslinker as well as
for the remaining 11 minutes of processing (material
temperature=262.degree. C.). The resulting physical blend was
molded and tested as above and results are presented in Table
A1.
[0113] Example A4
[0114] PET 1 was dried at 120.degree. C. for 6 hours to provide a
resin having a moisture content of 0.003%. BASE 1 (120.2 g) was
mixed at 100 rpm/setting of 250.degree. C., as described above.
After 4 minutes, 80.0 g of the dried PET 1 were added and this
combination mixed for 3 more minutes, whereupon 0.15 g of
IRGANOX.TM. 1010 was added. This combination was mixed for 4
minutes and 2.31 g of X-LINKER 1 were added. Mixing was continued
for another 6 minutes and 1.13 g (63 drops) of CATALYST 1 were
added. Within two minutes the torque increased from 1,200 m-g to a
maximum of 6,500 m-g. After the mixing was completed (24 minutes
total) the material temperature was 281 .degree. C. This TPSiV was
molded and tested as above and results are presented in Table
A1.
1TABLE A1 Tensile Strength Elongation Example (MPa) (%) (Comp.) Ex.
A1 1.37 13 (Comp.) Ex. A2 0.92 11 (Comp.) Ex. A3 1.0 9 Ex. A4 12.3
246
[0115] It can be seen from Table A1 that the physical blends had
significantly inferior mechanical properties relative to the TPSiV
of Example A4.
[0116] Examples A5-A7.
[0117] BASE 1 (120.0 g) was mixed at 60 rpm/setting of 250.degree.
C., as described in Example A4 but employing a nitrogen purge at a
flow rate of 10 SCFH (0.00472 m.sup.3/min). After 4 minutes, 80.0 g
of PET 1(dried at 120.degree. C./6 hours) were added and mixing was
continued for another 3 minutes, whereupon 0.16 g of IRGANOX.TM.
1010 was added. This combination was mixed for 5 minutes and then
1.20 g of X-LINKER 1 were added. The combination was mixed for an
additional 6 minutes and 0.565 g (31 drops) of CATALYST 1 was
introduced. Torque increased from 1,200 m-g to a maximum value of
4,100 m-g. Total processing time was 40 minutes and final material
temperature was 270.degree. C. (Example A5).
[0118] The procedures of Example A5 were followed wherein the level
of X-LINKER 1 was varied, as shown in the second column of Table
A2. Process time for Examples A6 and A7 were 30 min. and 26 min.,
respectively. Each resulting TPSiV was molded and tested, as
described above, and the results are shown in Table A2.
2TABLE A2 Tensile Maximum X-LINKER 1: Strength Elongation Torque
Example (Grams) (MPa) (%) (m-g) A5 1.2 5.6 47 4,100 A6 2.3 8.8 120
6,000 A7 4.59 9.6 134 10,000
[0119] Example A8
[0120] One hundred grams of BASE 1 were mixed at 100 rpm/setting of
250.degree. C., as described in Example A4. After 4 minutes, 100 g
of PET 1 (dried at 150.degree. C./5 hours) were introduced and
mixed for another 4 minutes, at which time 0.19 g of IRGANOX.TM.
1010 was added. Mixing was continued for an additional 4 minutes
and then 1.85 g of X-LINKER 1 was added. Six minutes later, 0.94 g
(52 drops) of CATALYST 1 was added and the torque increased from
900 m-g to 4,900 m-g in about 1 minute, at which point processing
was terminated. The resulting material was molded and tested, as
before, the results being presented in Table A3.
[0121] Example A9
[0122] One hundred and forty grams BASE 1 were mixed at 100
rpm/setting of 250.degree. C., as described in Example A4. After 4
minutes, 60 g of PET 1 (dried at 150.degree. C./5 hours) were added
and mixing was continued for another 4 minutes, at which time 0.11
g of IRGANOX.TM. 1010 was added. This combination was mixed for an
additional 4 minutes whereupon 2.67 g of X-LINKER 1 were added
(i.e., same ratio of crosslinker to silicone base as in Examples A4
and A8). Six minutes later, 1.32 g (73 drops) of CATALYST 1 were
added. Torque increased from 1,300 m-g to 7,000 m-g within about 2
minutes, at which point processing was terminated. The resulting
material was molded and tested, as before, the results being
presented in Table A3.
3 TABLE A3 Tensile BASE 1/PET 1 Strength Elongation Example Weight
Ratio (MPa) (%) A8 50/50 12.6 152 A4 60/40 12.3 246 A9 70/30 9.3
248
[0123] Examples A10-A13
[0124] The procedures of Example A4 were repeated using different
grades of poly(ethylene terephthalate) and employing a nitrogen
purge at a flow rate of 0.00472 m.sup.3/min. Mechanical properties
of the resulting TPSiVs are presented in Table A4.
4 TABLE A4 Tensile Strength Elongation Example Resin (MPa) (%) A10
PET 2 9.2 120 A11 PET 3 8.6 116 A12 PET 4 9.3 110 A13 PET 5 5.3
47
[0125] Example A14
[0126] BASE 2 (120.0 g) was mixed for 3 minutes at 100 rpm/setting
of 250.degree. C., as described above. After another 3 minutes,
80.0 g of PET 1 (dried at 130.degree. C./4.5 hours) were added and
mixing was continued for 4 more minutes, whereupon 0.15 g of
IRGANOX.TM. 1010 was added. This combination was mixed for 5
minutes and then 2.53 g of X-LINKER 1 were added. The combination
was mixed for an additional 6 minutes and 1.24 g (69 drops) of
CATALYST 1 were introduced. Torque increased from 900 m-g to a
maximum value of 6,000 m-g. Total processing time was 21 minutes
and final TPSiV temperature was 267.degree. C. The resulting
material was molded and tested, as before, and exhibited a tensile
of 7.0 MPa and elongation of 91%.
Example A15
[0127] PDMS 2 (120.0 g) was mixed for 4 minutes at 100 rpm/setting
of 250.degree. C., as described above. After another 4 minutes,
80.0 g of PET 1(dried at 130.degree. C. /4.5 hours) were added and
mixing was continued for 3 more minutes, whereupon 0.15 g of
IRGANOX.TM.1010 was added. This combination was mixed for 5 minutes
and then 3.01 g of X-LINKER 1 were added. The combination was mixed
for an additional 6 minutes and 1.50 g (83 drops) of CATALYST 1
were introduced. Torque increased from 600 m-g to a maximum value
of 5,300 m-g. Total processing time was 22 minutes and final TPSiV
temperature was 270.degree. C. The resulting material was molded
and tested, as before, and exhibited a tensile of 4.8 MPa and
elongation of 79%.
[0128] Examples A16-A22
[0129] TPSiVs based on PET 1 were prepared according to the
procedure of Example A4 with the exception that the resin was not
dried (moisture content varied between 0.12 and 0.13%), CATALYST 2
was used at a level of 0.25 g (14 drops) and crosslinker at a level
5.4 g. IRGANOX.TM.1010 stabilizer was either omitted or included,
as indicated in the second column of Table A5. The resulting
compositions were molded and tested, as before, and the mechanical
properties are also presented in Table A5.
5TABLE A5 IRGANOX .TM. 1010 Set Temp. Tensile Elongation Example
Included (.degree. C.) (MPa) (%) (Comp.) Ex. NO 275 4.7 16 A16*
(Comp.) Ex. NO 250 7.1 56 A17* (Comp.) Ex. NO 250 6.4 48 A18
(Comp.) Ex. NO 250 4.8 42 A19 Example YES 250 11 227 A20 (Comp.)
Ex. NO 250 4.3 9 A21 Example YES 250 10 177 A22 *Order of addition
was resin, followed by silicone base.
[0130] It can be seen from Table A5 that TPSiVs which included the
stabilizer had considerably better mechanical properties than
corresponding systems wherein this component was omitted.
[0131] (Comparative) Example B1
[0132] One hundred and twenty grams of BASE 1 were mixed at 100
rpm/setting of 250.degree. C., as described above. After 2 minutes,
80.0 g of PEN (dried at 170.degree. C./6 hours; water
content=0.001%) were added. The torque was 1,200 m-g at 8 minutes
into the run, at which point the resin was fully melted and a
uniform physical blend of silicone and resin was observed. Torque
decreased to 1,000 m-g during the remaining 10 minutes of
processing and final material temperature was 278.degree. C. This
physical blend was molded at 280.degree. C. and tested, as
described above, the results being presented in Table B1.
[0133] (Comparative) Example B2
[0134] A physical blend was prepared as in Comparative Example B1
with the exception that 0.16 g of IRGANOX.TM. 1010 was added to the
PEN/BASE 1 blend at 4 minutes into the run. Torque was 1,200 m-g at
7.5 minutes and then decreased over the next 11.5 minutes to 1,000
m-g, at which time processing was terminated (material temperature
was 278.degree. C.). Mechanical testing results are shown in Table
B1.
[0135] (Comparative) Example B3
[0136] A physical blend was prepared as in Comparative Example B2
with the exception that 2.24 g of X-LINKER 1 were added to the
PEN/BASE 1/ IRGANOX.TM. 1010 blend at 12 minutes into the run.
Torque was 1,000 m-g just after adding the crosslinker and remained
at that level for the remaining 7 minutes of processing. At
completion, material temperature was 276.degree. C. Mechanical
testing results are shown in Table B1.
[0137] Example B4
[0138] One hundred and twenty grams of BASE 1 were mixed at 100
rpm/setting of 250.degree. C., as described in Example B1 and,
after 2 minutes, 80.0 g of PEN (dried at 170.degree. C./4.5 hours)
were added. This combination was mixed for another 2 minutes, 0.16
g of IRGANOX.TM. 1010 was added and mixing was continued for 8
minutes, whereupon 2.33 g of X-LINKER 1 were added. After another 6
minutes of mixing, 1.13 g (63 drops) CATALYST 1 were added. Torque
increased from 1,600 m-g to a maximum of 7,000 m-g. When processing
was complete (20 minutes total), the material temperature was
280.degree. C. Mechanical testing results on this TPSiV are shown
in Table B1.
[0139] (Comparative) Example B5
[0140] A TPSiV was prepared as in Example B4 with the exception
that the IRGANOX.TM. 1010 was omitted. Mechanical testing results
on this TPSiV are shown in Table B1.
6TABLE B1 Tensile Strength Elongation Example (MPa) (%) (Comp.) Ex.
0.6 8 B1 (Comp.) Ex. 0.8 9 B2 (Comp.) Ex. 0.9 9 B3 Example B4 9.9
79 (Comp.) Ex. 8.3 47 B5
[0141] It can be seen from Table B1 that the physical blends
(Comparative Examples B1-B3) had dramatically inferior mechanical
properties relative to the TPSiV according to the invention
(Example B4). Furthermore, these properties were also reduced when
the hindered phenol was not included (Comparative Example B5).
[0142] (Comparative) Example C1
[0143] BASE 1 (144.0 g) was mixed at 100 rpm using a Haake.TM. 9000
bowl mixer (roller blades) at a temperature setting of 240.degree.
C. After 4 minutes, 96.0 g of PTT (dried at 150.degree. C./4;
moisture content=0.002%) were added. At the 7 minute mark, 0.20 g
of IRGANOX.TM. 1010 was added, followed by the addition of 2.71 g
of X-LINKER 1 at 12 minutes. Torque increased from 1,800 m-g to
2,400 m-g during the remaining 24 minutes of processing. The final
physical blend had a temperature of 245.degree. C. This blend was
molded for 4 minutes at 10 tons (99 KPa) and 250.degree. C.,
followed by cold pressing for an additional 4 minutes. Test results
are indicated in Table C1
[0144] Example C2
[0145] BASE 1 (144.0 g) was mixed at 100 rpm using a Haake.TM. 9000
bowl mixer at a temperature setting of 240.degree. C. After 4
minutes, 96.0 g of PTT (dried at 150.degree. C./4 hours; moisture
content=0.002%) were added. At the 7 minute mark, 0.20 g of
IRGANOX.TM. 1010 was added and mixed for an additional 5 minutes,
at which point 2.74 g of X-LINKER 1 were introduced. This
combination was mixed for another 6 minutes and then 1.35 g (75
drops) of CATALYST 1 were added, whereupon the torque increased
from 2,200 m-g to a maximum value of 12,000 m-g. After a total
process time of 20 minutes the resulting TPSiV temperature was
261.degree. C. This composition was molded and tested as described
in (Comparative) Example C1 and results are given in Table C1.
[0146] Example C3
[0147] BASE 1 (168.0 g) was mixed at 100 rpm using a Haake.TM. 9000
bowl mixer at a temperature setting of 240.degree. C. After 4
minutes, 72.1 g of PTT (dried at 150.degree. C./4 hours; moisture
content=0.002%) were added. At the 7 minute mark, 0.15 g of
IRGANOX.TM. 1010 was added and mixed for an additional 5 minutes,
at which point 3.2 g of X-LINKER 1 were introduced. This
combination was mixed for another 6 minutes and then 1.58 g (88
drops) of CATALYST 1 were added, whereupon the torque increased
from 2,600 m-g to a maximum value of 10,000 m-g. After a total
process time of 20 minutes the resulting TPSiV temperature was
254.degree. C. This composition was molded and tested as described
in (Comparative) Example C1 and results are given in Table C1.
7TABLE C1 Tensile Strength Elongation Example BASE 1/PTT Ratio
(MPa) (%) (Comp.) Ex. C1 60:40 1.8 7 (Physical Blend) Ex. C2 60:40
15.2 192 Ex. C3 70:30 10.7 154
[0148] (Comparative) Example D1
[0149] BASE 1 (144.0 g) was mixed for 3 minutes at 100 rpm and a
temperature setting of 20.degree. C. using roller blades and a
nitrogen purge flow rate of 0.5 SCFM (0.0142 m.sup.3/min.),
whereupon 0.36 g of IRGANOX.TM. 1010 was added. At the 6 minute
mark, 2.72 g of X-LINKER 1 were added followed by 96.0 g of PCT
resin (dried at 150.degree. C./7.5 hours), the latter being added
12 minutes into the run. This combination was mixed for an
additional 5 minutes and the resulting "cold blend" was then
removed from the mixer.
[0150] The above described cold blend (240 g) was charged to a
mixer and mixed at 100 rpm at a temperature setting of 270.degree.
C. for 11.5 minutes using a nitrogen purge (0.0142 m.sup.3/min.).
The resulting physical blend was molded and tested, the mechanical
properties being presented in Table D1.
[0151] Example D2
[0152] BASE 1 (144.0 g) was mixed for 3 minutes at 100
rpm/temperature setting of 20.degree. C., as described above, using
a nitrogen purge flow rate of 0.5 SCFM (0.0142 m.sup.3/min.) in a
Haake.TM. 9000 mixer (310 ml volume, roller blades) whereupon 0.37
g of IRGANOX.TM. 1010 was added. At the 6 minute mark 2.67 g of
X-LINKER 1 were added followed by 96.0 g of PCT resin (dried at
100.degree. C./6 hours; moisture content=0.025%), the latter being
added 12 minutes into the run. Mixing was continued for an
additional 4 minutes and the resulting "cold blend" removed.
[0153] The above-described cold blend (240.0 g) was mixed at 100
rpm/temperature setting of 270.degree. C. (under nitrogen at 0.0142
m.sup.3/min.) for 7 minutes and 1.35 g (75 drops) CATALYST 1 were
then introduced. Torque increased from 1,800 m-g to a maximum of
9,800 m-g. Upon completion (total process time=9.5 minutes) the
material temperature was 295.degree. C. The resulting TPSiV was
molded and tested, the mechanical properties being presented in
Table D1.
[0154] (Comparative) Example D3
[0155] A composition having the same proportions of ingredients as
described in Example D2 was prepared without benefit of the cold
blend procedure. The resulting TPSiV was molded and tested, as
described above, the mechanical properties being presented in Table
D1.
[0156] Example D4
[0157] A TPSiV based on PCT was prepared by mixing 120.2 g of BASE
1 and 1 g of IRGANOX.TM. 1010 at 100 rpm, set temperature of
295.degree. C. and N.sub.2 flow of 0.014 m.sup.3/min in a Haake.TM.
9000 Internal mixer. Eighty grams of PCT (dried at 100.degree. C.
for 8 hours to provide a resin having a moisture content of 0.013%)
were added and this combination was mixed for about 6 minutes,
whereupon 4.58 g of X-LINKER 1 were added. Mixing was continued for
another 4 minutes and 2 g of CATALYST 1 were added. Within one
minute the torque increased from 2,200 m-g to a maximum of 14,000
m-g. The resulting material was molded and tested as above and the
results are shown in Table D1.
8TABLE D1 Tensile Strength Elongation Example (MPa) (%) (Comp.) Ex.
D1 Not Measurable Not Measurable Ex. D2 6.3 60 (Comp.) Ex. D3 6.8
21 Example D4 9.8 38
[0158] These examples illustrate the type of routine
experimentation sometimes needed to determine the appropriate level
of stabilizer commensurate with a TPSiV having an elongation of at
least 30%. They also illustrate the advantage of the
above-described cold-blend procedure when the resin melt point
approaches the 300.degree. C. limit of the invention.
[0159] (Comparative) Example E1
[0160] In a first procedure, BASE 1(166.6 g) was mixed at 100
rpm/setting of 250.degree. C. in a Polylab.TM. 2 bowl mixer (300 ml
bowl, roller blades). After 2 minutes, 0.6 g of IRGAFOS.TM. 168 was
added. After another 6 minutes of homogenization, 3.76 g of
X-LINKER 1 was added. Torque remained steady (2,750-3,000 m-g)
until the addition of 52 drops of CATALYST 1. A minute after
addition of catalyst solution, torque rose from 2,800 to 4,900 m-g
and subsequently dropped to 3,500 m-g. This illustrates the
observation that this phosphite stabilizer prevents a mixture of
silicone base and crosslinker from crosslinking prematurely under
the above conditions. However, incorporation of this stabilizer
does allow the silicone to crosslink after addition of catalyst, as
in the case of stabilization with hindered phenol according to the
invention.
[0161] In a second procedure, 120 g of BASE 1 were mixed at 100
rpm's using a Haake Polylab.TM. bowl mixer at a temperature setting
of 250.degree. C. for 2 minutes prior to adding 0.61 g of
IRGAFOS.TM. 168. After about a minute of homogenization, 80.0 g of
PET 1 (dried at 150.degree. C. for 7 hours) were added. This
combination was blended for another 9 minutes prior to adding 2.28
g of X-LINKER 1. After another 6 minutes of homogenization, 63
drops of CATALYST 1 were added. Two minute after the addition of
catalyst solution, torque rose from 1,000 to 6,500 m-g. The
resulting TPSiV was molded and tested as described above and
exhibited an elongation of 29% and tensile of 4.9 Mpa.
[0162] (Comparative) Example E2
[0163] The first procedure of (Comparative) Example E1 was repeated
wherein WESTON.TM. W618G stabilizer replaced the IRGAFOS.TM. 168.
In this case, it was observed that the stabilizer did not prevent
premature crosslinking of silicone (i.e., the silicone base
crosslinked without addition of catalyst).
[0164] An attempt to prepare a TPSiV based on PET 1 using the
WESTON.TM. W618G stabilizer in place of IRGAFOS.TM. 168, as
described in (Comparative) Example E1, resulted in a composition
having an elongation of 9% and a tensile of 2.8 MPa.
[0165] (Comparative) Examples F1-F4
[0166] TPSiVs based on LCP resin were prepared according to the
methods described in Example A4 wherein mixing was carried out at a
set point of 336.degree. C. and the amount of IRGANOX.TM. 1010 was
varied, as shown in Table E1. Mechanical test results on samples
molded at 350.degree. C. are also presented in this table.
9 TABLE F1 (Comparative) Example F1 F2 F3 F4 Composition: BASE 1
(g) 120.2 120.2 120.7 120.33 LCP (g) 80.2 80.0 80.1 80.22 IRGANOX
.TM. 1010 (g) 0 0.15 0.5 1.0 X-LINKER 1 (g) 2.3 2.23 2.3 2.24
CATALYST 1 63 drops 63 drops 63 drops 63 drops (drops) Properties:
Tensile Strength (MPA) 7.4 7.4 20.6 17.3 Elongation (%) 8 7 26 24
Ultimate torque (m-g) 4,300 2,800 7,500 6700
[0167] It is seen from Table F1 that a thermoplastic elastomer
according to the invention could not be prepared from the LCP resin
without the use of a stabilizer. Moreover, even the use of a
relatively large proportion of stabilizer did not result in a TPSiV
having an elongation of at least 30%.
* * * * *