FIELD OF THE INVENTION
The present invention relates to thermoplastic vulcanizates
(TPVs) based on low Mooney, optionally hydrogenated nitrile polymers rubber and
polyamides. The present invention also relates to TPVs based on low Mooney, optionally
hydrogenated nitrile terpolymers and polyamides. TPVs prepared according to the
present invention have improved morphology, smaller rubber particle size, and improved
processibility compared to TPVs containing non-low Mooney, optionally hydrogenated
nitrile butadiene rubber. TPVs prepared according to the present invention are readily
formable by molding or extrusion, are recyclable, and display excellent heat and
oil-resistant properties that render them suitable for many industrial and automotive
BACKGROUND OF THE INVENTION
TPVs are two-phase systems wherein cured rubber particles
are finely dispersed in a thermoplastic phase. The mixing temperature must be high
enough to melt the thermoplastic phase and also cure the rubber. The curing of the
rubber phase occurs under conditions of dynamic vulcanization (curing the rubber
during melt mixing), contrary to static curing that typically occurs in a rubber
mold. Shearing must continue to be applied to prevent the agglomeration of the rubber
particles since small rubber particle size is critical in obtaining a product with
high performance. For TPVs to have good performance the following properties are
desired: (a) the surface energies of the two phases must match, (b) the molecular
weight between inter-chain entanglements in the rubber must be low, (c) thermoplastic
should have crystallinity, (d) the rubber should be cured at the mixing temperature,
and (e) both phases must be stable at the mixing temperature.
TPVs are processed by techniques commonly used in the plastics
industry such as injection molding which makes their fabrication more efficient
and cost-effective than thermosets. TPVs have non-Newtonian flow properties and
their viscosity is very shear dependent. At low shear rates, their viscosity increases,
flow diminishes, and they have a high retention of melt integrity and shape retention
when cooled. As the shear rate increases, they become more fluid and can be more
rapidly injected into a mould.
Thermoplastic elastomers find many applications, for example
in coatings, adhesives and in molded and extruded parts. The latter are valued for
their toughness and impact resistance, and find application in automotive parts,
mechanical parts, electrical parts and other uses.
Specific applications include: seals, wire covers, fuel
lines and hoses, cold-air intake tubes, and CVJ boots, pedals, grips, wipers, pipe
seals, electrical moldings, as well as injection molded housing and cabinetry for
Improvements in properties are being constantly sought,
and often for this purpose polymeric materials are mixed or blended.
EP-A1-0 364 859
relates to vulcanizable rubbery compositions containing a polyamide, a
partially hydrogenated nitrile rubber and curatives in the nitrile rubber. The partially
hydrogenated nitrile rubber, admixed with a curing agent, was gradually added to
molten polyamide, with mixing. It is stated that it is preferred to use a polyamide
having a low melting point, such as nylon 12. In a preferred embodiment the composition
includes maleic anhydride or succinic anhydride. The specification states that the
anhydride additive improves mixing between the nylon and the rubber compound. Better
results are obtained in an example in which maleic anhydride is used, but the properties
of the product obtained are not particularly good, and are not adequate for commercial
U.S. Patent No. 4,508,867
relates to vulcanizable rubbery compositions containing a crystalline
polyamide, a synthetic rubbery polymer composed of acrylonitrile or methacrylonitrile,
an &agr;,&bgr;-unsaturated carboxylic acid and butadiene, an additive selected
from the halides of lithium, magnesium, calcium and zinc, an additive selected from
the oxides and hydroxides of magnesium, calcium, barium and zinc and the peroxides
of calcium and zinc and further contains sulfur vulcanization active agents. Nylon
11 is the only polyamide whose use is exemplified.
The descriptive portion of the specification suggests that
the mixing of the polyamide and the synthetic rubbery polymer should take place
at a temperature in the range of from about 50 to about 125°C. In Examples
1 and 2 mixing of nylon 11 and carboxylated nitrile rubber, and other ingredients,
took place at 50°C. In Example 3 mixing took place at 190 to 199°C and
Example 4 does not specify the temperature of mixing. It is believed that the compositions
U.S. Patent No. 4,508,867
do not display adequate heat resistant properties.
WO 03/020820 A1
describes the preparation of heat and oil resistant polymer blends of
polyamides and hydrogenated carboxylated nitrile rubber prepared according to a
single step process.
Co-pending US Patent Application filed on December 12,
2004 entitled "Multistage Process for the Manufacture of Peroxide Cured HXNBR-Polyamide
Thermoplastic Vulcanizates" discloses TPVs having improved morphology and smaller
rubber particle size than those previously discovered.
SUMMARY OF THE INVENTION
The present invention relates to thermoplastic vulcanizates
(TPVs) based on low Mooney, optionally hydrogenated nitrile butadiene rubber and
The present invention also relates to thermoplastic vulcanizate
(TPV) based on low Mooney, optionally hydrogenated nitrile terpolymers and polyamides.
The present invention also relates to a process for preparing
thermoplastic vulcanizates (TPVs) based on low Mooney, optionally hydrogenated nitrile
butadiene rubber or low Mooney, optionally hydrogenated nitrile terpolymers, and/or
mixtures thereof and polyamides. The process according to the present invention
can involve one or more stages.
BRIEF DESCRIPTION OF THE DRAWINGS
DETAILED DESCRIPTION OF THE INVENTION
- Figure 1 illustrates the MPT (Monsanto Processibility Tester) of TPVs prepared
with low Mooney hydrogenated nitrile terpolymers and non-low Mooney hydrogenated
- Figure 2A and AB compare the morphology (TEM: Transmission Electron Microscopy)
of a low Mooney hydrogenated nitrile terpolymer to a non-low Mooney hydrogenated
- Figure 3 illustrates the viscosities of Examples 5 and 6 at different shear
Also, all ranges include any combination of the maximum
and minimum points disclosed and include any intermediate ranges therein, which
may or may not be specifically enumerated herein.
Polyamides useful in the present invention include homopolymers
and copolymers that have repeated amide linkages along a polymer chain. The polyamides
are preferably of high molecular weight and are crystalline or glossy polymers.
Examples include polycaprolactam (nylon 6), polylaurolactam (nylon 12), polyhexamethyleneadipamide
(nylon 6,6), polyhexamethyleneazelamide (nylon 6,9), polyhexamethylenesebacamide
(nylon 6,10), polyhexamethyleneisophthalamide (nylon 6,IP), polyaminoundecanoic
acid (nylon 11), polytetramethyleneadipamide (nylon 4,6) and copolymers of caprolactam,
hexamethylenediamine and adipic acid (nylon 6,66), and also aramids such as polyparaphenylene-terephthalamide.
The majority of the polyamides useful in the present invention have softening points
and melting points in the range of from 160 to 250°C.
As used throughout this specification, the term "nitrile
rubber", "nitrile polymer" or NBR is intended to have a broad meaning and is meant
to encompass a copolymer having repeating units derived from at least one conjugated
diene and at least one &agr;,&bgr;-unsaturated nitrile.
The low Mooney, optionally hydrogenated nitrile rubbers
useful in the present invention and processes for making them are known in the art
and are the subject of
U.S. Patent Nos. 6,673,881
the disclosure of which is incorporated by reference for the purpose of
Jurisdictions allowing for this feature. Such rubbers are formed by the olefin metathesis
of nitrile butadiene rubber with a Ru metathesis catalyst, such as a Grubb's catalyst,
followed optionally by hydrogenation of the resulting metathesized NBR.
Low Mooney nitrile polymers useful in the present invention
have a Mooney viscosity (ML(1 +4) @ 100°C) of below 25, preferably below 20,
more preferably below 15 and most preferably below 10.
Low Mooney hydrogenated nitrile polymers useful in the
present invention have a Mooney viscosity (ML(1+4) @ 100°C) of between 1 and
55, preferably between 5 and 50, more preferably between 10 and 45 and most preferably
between 15-40. Low Mooney hydrogenated nitrile polymers useful in the present invention
have a polydispersity index of less than 2.5.
As used throughout this specification, the term "nitrile
terpolymer rubber" or "LT-NBR" is intended to have a broad meaning and is meant
to encompass a copolymer having (a) repeating units derived from at least one conjugated
diene, (b) at least one &agr;,&bgr;-unsaturated nitrile, (c) repeating units
derived from at least one further monomer selected from the group consisting of
conjugated dienes, unsaturated carboxylic acids; alkyl esters of unsaturated carboxylic
acids, alkoxyalkyl acrylates and ethylenically unsaturated monomers other than dienes
and (d) optionally further copolymerizable monomer(s). If (a) and (c) are conjugated
dienes, it is understood that the nitrile terpolymer rubber comprises repeating
units derived from at least two different conjugated dienes.
The low Mooney, optionally hydrogenated nitrile terpolymers
useful in the present invention and processes for making them are not known in the
art and are the subject of co-pending US Patent Application filed concurrently herewith
and entitled "Process for the Preparation of Low Mooney Nitrile Terpolymers" the
disclosure of which is incorporated by reference for the purpose of Jurisdictions
allowing for this feature. Such rubbers are formed by the olefin metathesis of nitrile
terpolymers with a Ru metathesis catalyst, such as a Grubb's catalyst, followed
optionally by hydrogenation of the resulting metathesized nitrile terpolymers.
Low Mooney nitrile terpolymer rubbers useful in the present
invention have a Mooney viscosity (ML(1+4) @ 100°C) of below 25, preferably
below 20, more preferably below 15 and most preferably below 10.
Low Mooney hydrogenated nitrile terpolymer rubbers useful
in the present invention have a Mooney viscosity (ML(1+4) @ 100°C) of between
1 and 55, preferably between 5 and 50, more preferably between 10 and 45 and most
preferably between 15-40. Low Mooney hydrogenated nitrile terpolymers useful in
the present invention have a polydispersity index of less than 2.5.
The conjugated diene may be any known conjugated diene
in particular a C4-C6 conjugated diene. Preferred conjugated
dienes are butadiene, isoprene, piperylene, 2,3-dimethyl butadiene and mixtures
thereof. Even more preferred C4-C6 conjugated dienes are butadiene,
isoprene and mixtures thereof. The most preferred C4-C6 conjugated
diene is butadiene.
The &agr;,&bgr;-unsaturated nitrile may be any known
&agr;,&bgr;-unsaturated nitrile, in particular a C3-C5
alpha,beta-unsaturated nitrile. Preferred C3-C5 &agr;,&bgr;-unsaturated
nitriles are acrylonitrile, methacrylonitrile, ethacrylonitrile and mixtures thereof.
The most preferred C3-C5 alpha,beta-unsaturated nitrile is
The unsaturated carboxylic acid may be any known unsaturated
carboxylic acid copolymerizable with the other monomers, in particular a C3-C16
&agr;,&bgr;-unsaturated carboxylic acid. Preferred unsaturated carboxylic acids
are acrylic acid, methacrylic acid, itaconic acid and maleic acid and mixtures thereof.
The alkyl ester of an unsaturated carboxylic acid may be
any known alkyl ester of an unsaturated carboxylic acid copolymerizable with the
other monomers, in particular an alkyl ester of an C3-C16
&agr;,&bgr;-unsaturated carboxylic acid. Preferred alkyl ester of an unsaturated
carboxylic acid are alkyl esters of acrylic acid, methacrylic acid, itaconic acid
and maleic acid and mixtures thereof, such as butyl acrylate, methyl acrylate, 2-ethylhexyl
acrylate and octyl acrylate. Preferred alkyl esters include methyl, ethyl, propyl,
and butyl esters.
The alkoxyalkyl acrylate may be any known alkoxyalkyl acrylate
copolymerizable with the other monomers, preferably methoxyethyl acrylate, ethoxyethyl
acrylate and methoxyethoxyethyl acrylate and mixtures thereof.
The ethylenically unsaturated monomer may be any known
ethylenically unsaturated monomer copolymerizable with the other monomers, preferably
allyl glycidyl ether, vinyl chloroacetate, ethylene, butene-1, isobutylene and mixtures
An antioxidant may be useful in the preparation of TPVs
according to the present invention. Examples of suitable antioxidants include Naugard®
445 (p-dicumyl diphenylamine), Vulkanox® DDA (a diphenylamine derivative),
Vulkanox® ZMB2 (zinc salt of methyl-mercapto benzimidazole), Vulkanox®
HS (polymerized 1,2-dihydro-2,2,4-trimethyl quinoline) and Irganox®
1035 (thiodiethylene bis(3,5-di-tert.-butyl-4-hydroxy) hydroxy cinnamate or thiodiethylene
bis(3-(3,5-di-tert.-butyl-4-hydroxyphenyl)propionate supplied by Ciba Specialty
Suitable peroxide curatives useful in the preparation of
TPVs according to the present invention include dicumyl peroxide, di-tert.-butyl
peroxide, benzoyl peroxide, 2,2'-bis (tert.-butylperoxy diisopropylbenzene (Vulcup®
40KE), benzoyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)-hexyne-3, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane,
(2,5-bis(tert.-butyl peroxy)-2,5-dimethyl hexane and the like can be used. The high
temperature of the polyamide melt influences the selection, however. The best suited
curing agents are readily accessible by means of a few preliminary experiments.
A preferred peroxide curing agent is commercially available under the trademark
Vulcup® 40KE. The peroxide curing agent is suitably used in an amount
of 0.2 to 7 parts per hundred parts of rubber (phr), preferably 1 to 3 phr. Too
much peroxide may lead to undesirably violent reaction. Sulphur, sulphur-containing
compounds and resins can also be used as curatives.
Vulcanizing co-agents can also be used in the preparation
of TPVs according to the present invention. Mention is made of triallyl isocyanurate
(TAIC), commercially available under the trademark DIAK®7 from DuPont
or N,N'-m-phenylene dimaleimide know as HVA-2 (DuPont Dow), triallyl cyanurate (TAC)
or liquid polybutadiene known as Ricon® D 153 (supplied by Ricon
Resins). Amounts can be equivalent to the peroxide curative or less, preferably
Crosslinking density can further be increased by the addition
of an activator such as zinc peroxide (50% on an inert carrier) using Struktol®
ZP 1014 in combination with the peroxide. Amounts can be between 0.2 to 7 phr, preferably
1 to 3 phr.
It is possible to achieve further crosslinking by using
curatives used with carboxylated polymers such as: amines, epoxides, isocyanates,
carbodiimides, aziridines, or any other additive that can form a derivative of a
The ratio of polyamide to low Mooney, optionally hydrogenated
nitrile rubber and/or low Mooney, optionally hydrogenated terpolymer can vary between
wide limits, preferably 90 parts to 10 parts by weight to 10 parts to 90 parts by
weight. More preferable combinations include 40-10 parts polyamide and 60-90 parts
rubber. Properties of the conjugate vary, depending on the ratio of polyamide to
elastomer. The ratio of polyamide to rubber can vary and can be optimized by simple
experimentation by one skilled in the art.
It is possible to include processing oils and extenders
or plasticizers in the TPV according to the present invention. Suitable plasticizers
include those well known for use with nitrile polymers such as the phthalate compounds,
the phosphate compounds, the adipate compounds, the alkyl carbitol formal compounds,
the coumarone-indene resins and the like. An example is the plasticizer commercially
available under the trademark Plasthall 810, or Plasthall TOTM (trioctyl trimellitate)
or TP-95 (di-(butoxy-ethoxy-ethyl) adipate supplied by Morton International. The
plasticizer should be a material that is stable at high temperature and will not
exude from the conjugate. If plasticizer is to be used it is preferred to melt the
polyamide, add a first portion of the hydrogenated carboxylated nitrile rubber,
say about half, mix, then add the plasticizer, mix and then add the remainder of
the low Mooney, optionally hydrogenated, nitrile rubber or low Mooney, optionally
hydrogenated, nitrile terpolymer and continue mixing. The amount of plasticizer
used will depend upon the proposed end use of the TPV, but may be between 1 and
40 phr, preferably between 5 and 20 phr. It is further possible to use a blend of
It is also possible to use a mixture of optionally hydrogenated
low Mooney nitrile rubbers thereof or low Mooney nitrile terpolymers and another
elastomer, for example, a carboxylated nitrile rubber (XNBR), a hydrogenated nitrile
rubber (HNBR) or a nitrile rubber (NBR), a vinyl acetate rubber (EVM) or a ethylene/acrylate
rubber (AEM) or a hydrogenated carboxylated nitrile rubber (HXNBR). Suitable XNBRs
are commercially available from Lanxess Deutschland GmbH under the trademark Krynac®
and suitable HNBRs are commercially available from Lanxess Deutschland GmbH under
the trademark Therban® and suitable NBRs are available from Lanxess
Deutschland GmbH under the trademark Perbunan®. EVM is commercially
available from Lanxess Deutschland GmbH under the trademark Levapren®.
Vamac® D an ethylene acrylic elastomer is commercially available
The present inventive TPV can also contain at least one
filler. The filler may be an active or inactive filler or a mixture thereof. The
filler may be in particular:
or mixtures thereof.
- highly dispersed silicas, prepared e.g. by the precipitation of silicate solutions
or the flame hydrolysis of silicon halides, with specific surface areas of in the
range of from 5 to 1000 m2/g, and with primary particle sizes of in the range of
from 10 to 400 nm; the silicas can optionally also be present as mixed oxides with
other metal oxides such as those of Al, Mg, Ca, Ba, Zn, Zr and Ti;
- synthetic silicates, such as aluminum silicate and alkaline earth metal silicate
like magnesium silicate or calcium silicate, with BET specific surface areas in
the range of from 20 to 400 m2/g and primary particle diameters in the range of
from 10 to 400 nm;
- natural silicates, such as kaolin and other naturally occurring silica;
- glass fibers and glass fiber products (matting, extrudates) or glass microspheres;
- carbon blacks; the carbon blacks to be used here are prepared by the lamp black,
furnace black or gas black process and have preferably BET (DIN 66 131) specific
surface areas in the range of from 20 to 200 m2/g, e.g. SAF, ISAF, HAF, FEF or GPF
- rubber gels, especially those based on polybutadiene, butadiene/styrene copolymers,
butadiene/acrylonitrile copolymers and polychloroprene;
Examples of preferred mineral fillers include silica, silicates,
clay such as bentonite, gypsum, alumina, titanium dioxide, talc, mixtures of these,
and the like. These mineral particles have hydroxyl groups on their surface, rendering
them hydrophilic and oleophobic. This exacerbates the difficulty of achieving good
interaction between the filler particles and the rubber. For many purposes, the
preferred mineral is silica, especially silica made by carbon dioxide precipitation
of sodium silicate.
Dried amorphous silica particles suitable for use in accordance
with the invention may have a mean agglomerate particle size in the range of from
1 to 100 microns, preferably between 10 and 50 microns and most preferably between
10 and 25 microns. It is preferred that less than 10 percent by volume of the agglomerate
particles are below 5 microns or over 50 microns in size. A suitable amorphous dried
silica moreover usually has a BET surface area, measured in accordance with DIN
(Deutsche Industrie Norm) 66131, of in the range of from 50 and 450 square meters
per gram and a DBP absorption, as measured in accordance with DIN 53601, of in the
range of from 150 and 400 grams per 100 grams of silica, and a drying loss, as measured
according to DIN ISO 787/11, of in the range of from 0 to 10 percent by weight.
Suitable silica fillers are available under the trademarks HiSil®
210, HiSil® 233 and HiSil® 243 from PPG Industries
Inc. Also suitable are Vulkasil® S and Vulkasil®
N, from Lanxess Deutschland GmbH.
The TPV according to the present invention can contain
further auxiliary products suitable for use with rubbers, such as reaction accelerators,
vulcanizing accelerators, vulcanizing acceleration auxiliaries, antioxidants, foaming
agents, anti-aging agents, heat stabilizers, light stabilizers, ozone stabilizers,
processing aids, plasticizers, tackifiers, blowing agents, dyestuffs, pigments,
waxes, extenders, organic acids, inhibitors, metal oxides, and activators such as
triethanolamine, polyethylene glycol, hexanetriol, etc., which are known to the
rubber industry. The rubber aids are used in conventional amounts, which depend
inter alia on the intended use. Conventional amounts include from 0.1 to 50 wt.%,
based on rubber. Preferably the TPV contains in the range of 0.1 to 20 phr of an
organic fatty acid as an auxiliary product, preferably a unsaturated fatty acid
having one, two or more carbon double bonds in the molecule which more preferably
includes 10% by weight or more of a conjugated diene acid having at least one conjugated
carbon-carbon double bond in its molecule. Preferably those fatty acids have in
the range of from 8-22 carbon atoms, more preferably 12-18. Examples include stearic
acid, palmitic acid and oleic acid and their calcium-, zinc-, magnesium-, potassium-
and ammonium salts. Preferably the TPV includes in the range of 5 to 50 phr of an
acrylate as an auxiliary product. Suitable acrylates are known from
EP-A1-0 319 320
U.S. Patent Nos. 5,208,294
. Reference is made to zinc acrylate, zinc diacrylate or zinc dimethacrylate
or a liquid acrylate, such as trimethylolpropanetrimeth-acrylate (TRIM), butanedioldimethacrylate
(BDMA) and ethylenglycoldimeth-acrylate (EDMA). It might be advantageous to use
a combination of different acrylates and/or metal salts thereof. Of particular advantage
is often to use metal acrylates in combination with a Scorch-retarder such as sterically
hindered phenols (e.g. methyl-substituted aminoalkylphenols, in particular 2,6-di-tert.-butyl-4-dimethylamino-methylphenol).
It is possible to incorporate other known additives or compounding agents in the
TPV according to the present invention.
The TPVs of the present invention can be prepared according
to a single stage or a multi-stage process. According to a single step process,
the polyamide can be melted and the optionally hydrogenated low Mooney nitrile rubber
or nitrile terpolymer is then added to the melt along with the additives, with stirring
in an intensive mixer such as a Banbury or in a high-shear extruder. The mixing
temperature of a single step process can range from 150°C to 300°C, preferably
from 170°C to 270°C and more preferably from 200°C to 250°C,
depending upon the polyamide grade. Suitable single step processes for use in the
present invention are disclosed in
CA Patent Application No. 2,356,580
Also, the TPV of the present invention can be prepared
according to a multi-stage process, the first stage involves mixing a polyamide
with the optionally hydrogenated low Mooney nitrile rubber or nitrile terpolymer
under high shear with the needed additives. Suitable mixing temperature can range
from 100°C to 300°C, preferably from 150 to 240°C, depending upon
the polyamide grade. In a second stage according to the present invention, the curative
is added to perform dynamic vulcanization and cure the rubber particles under conditions
of high shear. It is important that the curative used be added at temperatures where
it can be incorporated in such a manner that the curing and mixing rates are controlled.
Preferably the curative is added at a temperature below the melting point of the
polyamide incorporated in step 1, more preferably at a temperature in the range
of between 150 to 240°C, most preferably between 180 to 220°C. After curative
addition and dispersion, mixing conditions are adjusted to cause a quick temperature
increase to achieve dynamic vulcanization. This necessitates the careful selection
of the peroxide and the control of the mixing temperatures and shear conditions.
Also according to the present invention, the process for
preparing TPV's can be performed in three stages. The first stage includes preparing
a masterbatch of rubber, stabilizers, fillers, plasticizers, and other needed additives.
The second stage including intimately mixing of the masterbatch from stage one with
a polyamide. The third including dynamically vulcanizing of the blend from stage
two to obtain a TPV according to the present invention.
The invention is further illustrated but is not intended
to be limited by the following examples in which all parts and percentages are by
weight unless otherwise specified.
Comparative Example 1 was a terpolymer of carboxylated
nitrile butadiene rubber (Perbunan® VP KA 8877 available from LANXESS
Corporation) having 33 wt% acrylonitrile; 5 wt% methacrylic acid; and a Mooney viscosity,
ML(1+4) @ 100° C of 31.
Inventive Example 1 was prepared according the process
discussed in detail below via a metathesis reaction with Comparative Example 1.
Preparation of Low- Mooney, optionally hydrogenated terpolymers
The metathesis reactions of Examples 1 and 2 were conducted
with a 15% total solid and MCB (Monochlorobenzene) was used as the solvent. The
Grubb's II catalyst ([1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidiniylidene] dichloro(phenylmethylene)(tricyclohexylphosphine)
and 1-hexene were added to the terpolymer cement and shaken overnight at 25°C
in a glass container.
Comparative Example 2 and Inventive Example 2 were prepared
by hydrogenating the Comparative Example 1 terpolymer and Inventive Example 1 terpolymer
according to the following subsequent process: The following metathesis contents
from the procedure above were then transferred to the reactor in addition to ESBO
(Epoxidized Soybean Oil) for hydrogenation. Hydrogenation reactions were carried
out in a 0.5 US gallon Parr highpressure reactor under the following conditions:
Preparation of TPV Compounds (Examples 3 and 4)
Comparative Example 3
Table 1: Low Mooney Terpolymers
Metathesis Catalyst (phr)
ML(1+4) @ 100C
Hydrogenated Nitrile Terpolymers
2 (Hydrogenated Comp. Ex. 1)
2 (Hydrogenated Inv. Ex. 1)
* Both terpolymers
where hydrogenated to > 99%. This corresponds to RDB (Residual Double Bond content)
In the first step, 60 phr of HXNBR (Comparative Example
2) and 40 phr of polyamide 6 (Durethan® C 38 F) were blended in
the presence of antioxidant Naugard® 445, and process aids: Armeen
18D and Vanfre Vam. The polyamide 6 was melted and the mixture was very well mixed.
In the second stage the peroxide (3.5 phr of Vulcup 40KE and 2.2phr Struktol ZP
1014) were added in a temperature range of between 150-220°C to the blend prepared
from stage 1 and dynamic vulcanization was achieved under high shear conditions.
1 phr of antioxidant Irganox 1035 (thiodiethylene bis(3,5-di-t-butyl-4-hydroxy)
hydrocinnamate or thiodiethylene bis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate
supplied by Ciba Specialty Chemicals was added before the mixing was stopped. The
final temperatures in both stages were around 240°C.
The Brabender mixing conditions for the two stages were
as follows: 75% fill factor; 95 rpm mixing blade speed; the temperature range was
150-240°C; 15-20 minutes total mixing time (stage 1 + 2). Tables 2 and 3 show
the formulations and stress-strain data of the TPVs.
Inventive Example 4
Same mixing procedure as Example 3 above except that Inventive
Example 2 terpolymer (low Mooney HXNBR) was used.
Table 2: Formulation for TPVs
C 38 F
Terpolymer - Comparative
Terpolymer - Inventive
18D is an octadecylamine available from AkzoNobel and is used to reduce compound
stickiness to metal.
Durethan® C 38 F is a polyamide from Lanxess Deutschland GmbH.
Naugard® 445 (p-dicumyl diphenyl amine) is a stabilizer from Uniroyal.
Vanfre VamTM is a phosphate process aid from R.T. Vanderbilt.
Struktol™ ZP 1014 (Zinc Peroxide 50% on inert carrier).
Vulcup® 40 KE(&agr;,&bgr;-bis(t-butylperoxy)diisopropylbenzene),
Irganox® 1035 is a stabilizer (thiodiethylene bis(3,5-di-t-butyl-4-hydroxy)
Table 3: Stress-strain data
Hardness Shore A2
Ultimate Tensile (MPa)
Stress @ 50 (MPa)
Stress @ 100 (MPa)
The data illustrates Example 4 which contains the HXNBR
having a Mooney viscosity of 45 (Inventive Example 2) has very similar physical
properties to Example 3 containing the HXNBR having a Mooney viscosity of 81 of
Comparative Example 2. This indicates that using a lower money nitrile terpolymer
rubbers in such thermoplastic elastomer compositions does not deteriorate the performance
and properties of such compositions.
Figure 1 illustrates the viscosities of the two TPV compounds
at different shear rates. The viscosities were measured at 260°C by MPT (Monsanto
Processibility Tester, Capillary Rheometer). The data shows that Example 4, containing
Inventive Example 2 lower Mooney HXNBR has lower viscosity at all shear rates indicating
better processibility compared to Example 3, containing Comparative Example 2 HXNBR.
This shows that the inventive process of making low Mooney HNBR and the process
of blending them with a polyamide leads to thermoplastic elastomer compositions
with improved flow and processibility characteristics.
Figure 2 illustrates the TEM images (Transmission Electron
Microscope) of Examples 3 and 4. The samples where stained with osmium oxide to
get a color contrast between the rubber and plastic phases. The light and dark domains
correspond to the rubber and plastic phases respectively. The images show that phase
inversion (rubber dispersed in plastic) is achieved in both cases. Note the smaller
rubber particle size and improved morphology of Example 4. In contrast, the image
of Example 3 has larger rubber particle size and a coarser morphology. This shows
that using a lower Mooney nitrile terpolymers leads to better morphology, finer
dispersion, and a larger number of smaller rubber particles. This is especially
important since it is known to those skilled in the art that smaller rubber particle
size and finer dispersion leads to improved mechanical properties of such thermoplastic
Preparation of TPV Compounds
Examples 5 and 6 were prepared according to the process
discussed above, however the following examples contain blends of hydrogenated nitrile
rubber according to table 4.
Table 4: Formulation
C 38 F
AT VP KA 8966
XT VP KA 8889
STRUKTOL ZP 1014
A3407 (HNBR from Lanxess Deutschland GmbH; 34wt% Acrylonitrile; Mooney viscosity,
ML(1+4) @ 100°C = 70)
Therban® AT VP KA 8966 (low Mooney HNBR from Lanxess Deutschland
GmbH; 34wt% Acrylonitrile; Mooney viscosity, ML(1+4) @ 100°C = 39)
Therban® XT 8889 (HXNBR from Lanxess Deutschland GmbH.)
Figure 3 illustrates the viscosities of the Examples 5
and 6 at different shear rates. The viscosities were measured at 260°C by MPT
(Monsanto Processibility Tester, Capillary Rheometer). The data shows that Example
6, containing Therban® AT VP KA 8966 has lower viscosity at all shear rates
indicating better processibility compared to Example 5 containing Therban®
A3407. This illustrates that using an HNBR blend containing a low Mooney HNBR and
the process of blending it with nylon also leads to thermoplastic elastomer compositions
with improved flow and processibility characteristics.
Although the invention has been described in detail in
the foregoing for the purpose of illustration, it is to be understood that such
detail is solely for that purpose and that variations can be made therein by those
skilled in the art without departing from the spirit and scope of the invention
except as it may be limited by the claims.