Note: Descriptions are shown in the official language in which they were submitted.
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Room temperature curing system
Field of the Invention.
The present invention relates to a nitrite polymer composition comprising
at least one carboxylated nitrite rubber polymer, that is optionally
hydrogenated, at least one curing agent, and optionally at least one solvent,
a
process for preparing said polymer composition comprising at least one
hydrogenated carboxylated nitrite rubber polymer, at least one curing agent,
and optionally at least one solvent comprising the steps of hydrogenating at
least one carboxylated nitrite rubber polymer in solution, optionally
purifying
said solution, and admixing it with at least one curing agent and a self
supporting shaped article comprising said compound optionally layered on or
interposed between one or more supporting means. In still another of its
aspects, the present invention relates to a sealant composition comprising
said
nitrite polymer composition.
Back ro4 and of the Invention
Carboxylated hydrogenated nitrite rubber (HXNBR), prepared by the
selective hydrogenation of carboxylated acrylonitrile-butadiene rubber
(nitrite
rubber; XNBR, a co-polymer comprising at least one conjugated diene, at least
one unsaturated nitrite, at least one carboxylated monomer and optionally
further comonomers) and XNBR itself, are specialty rubbers which have very
good heat resistance, excellent ozone and chemical resistance, and excellent
oil resistance. Coupled with the high level of mechanical properties of the
rubber (in particular the high resistance to abrasion) it is not surprising
that
XNBR and HXNBR have found widespread use in the automotive (seals,
hoses, bearing pads) oil (stators, well head seals, valve plates), electrical
(cable sheating), mechanical engineering (wheels, rollers) and shipbuilding
(pipe seals, couplings) industries, amongst others.
Most commercially available curable compositions comprising XNBR
and/or HXNBR require elevated temperatures for curingfcross-linking which
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sometimes is not desirable and/or not possible, in particular when the
intended
use is as adhesive, coating or sealant.
Adhesives (glues) are substances capable of forming and maintaining a
bond between two surfaces, and sealants (caulks) are substances used to fill
gaps or joints between two materials to prevent the passage of liquids, solids
or gases. These two classes of materials are often considered together
because quite frequently a given formulation performs the both functions.
Sealants are available as one-component solvent evaporation curing
products and as chemical curing systems. With one-component solvent
evaporation curing products there is no curing process, the compound gets its
functionality through solvent loss and/or a decrease in temperature. When a
sealant is applied, the solvent evaporates or migrates into porous substrates
and the tough, rubbery compound is left in place. This is in contrast to other
sealant types that cure chemically.
XNBR and/or HXNBR coatings are desirable whenever the very good
heat resistance, excellent ozone and chemical resistance, and excellent oil
resistance provided by the XNBR and/or HXNBR should be transferred to
substrates such as plastics, rubbers, metal, glass and so on.
U.S. Pat. No 4,774,288 discloses a hydrogenated copolymer of a
conjugated diene and an alpha-beta-unsaturated nitrite containing an active
phenol-formaldehyde resin vulcanization system. The disclosure is directed to
the bulk vulcanizate, which is characterized as having good compression set
properties and a good resistance to oils and good resistance to oxidative
attack
in air at elevated temperature aging under oxidizing conditions, however no
mention is made suggesting coatings could be formed on flexible elastomeric
substrates such as natural rubber and polybutadiene which might provide
useful properties.
U.S. Pat. No. 5,314,741 discloses a coating composition including a
latex of highly saturated polymer such as hydrogenated nitrite rubber, highly
saturated styrene-butadiene copolymer, hydrogenated poiybutadiene, or
hydrogenated styrene-vinylpyridine-butadiene terpolymer. The coating is
applied to a substrate and cured in place to yield a desired coated article
reportedly resistant to ozone, oxygen, and UV light. Suitable curatives taught
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are zinc-sulfur cure packages. Elevated temperatures are utilized to affect
curing of these coatings. Moreover, conventional vulcanizing systems high in
sulfur content and low vulcanization accelerator content, or semi-efficient
vulcanizing system having a moderate dosage of sulfur and vulcanizates
accelerator have several drawbacks. Conventional vulcanizing systems
resulting in vulcanizates with good resistance to dynamic stresses (flex life)
are
very sensitive to aging and reversion. Semi-efficient vulcanizing systems
usually give vulcanizates which have a less of a resistance to dynamic
stresses
(flex life), but, in return, they are somewhat more stable to aging and
reversion.
U.S. Pat. No. 5,314,955 discloses a coating composition consisting of a
hydrogenated acrylonitrile-butadiene copolymer, a phenolic resin, a curing
component, and a solvent. This coating solves many of the problems of
adhesion to rubber substrates combined with fatigue resistance and fuel
resistance. One of the drawbacks of this coating composition is that it
requires
a high temperature bake to cure the coating and to promote adhesion to
adjacent metal surfaces. A high temperature bake requires heat soaking of the
entire article to be coated. Some parts such as helicopter rotor bearings
would
be damaged by a high temperature bake, therefore coatings such as taught in
'955 are not practical to apply. The high temperature bake is also costly in
production since it adds a time delay and additional handling of the parts.
US-Appl. No. 2003/0152790-A1 discloses a coating composition
comprising a functionalized hydrogenated acrylonitrile-butadiene copolymer,
(functionalized HNBR), a curing component which contains at least one
isocyanate group, preferably a polyisocyanate, or at least one isocyanate
group and a group which forms crosslinks, and a solvent. As the skilled in the
art is well aware of, isocyanates are harmful substances often linked to
cancer
development.
A need exists for an improved protective coating for flexible elastomeric
substrates which provide improved adhesion to the surface of elastomers, and
improved flex-resistance.
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Summary of the invention
In one of it's aspects, the present invention relates to a nitrite polymer
composition comprising (a) at least one carboxylated nitrite rubber polymer,
that is optionally hydrogenated, (b) at least one compound containing 2 or
more aziridine functional groups, and (c) optionally at least one solvent.
In another one of it's aspects, the present invention relates to a process
for preparing said polymer composition comprising (a) at least one
hydrogenated carboxylated nitrite rubber polymer, (b) at least one compound
containing 2 or more aziridine functional groups, and (c) at least one solvent
comprising the steps of hydrogenating at least one carboxylated nitrite rubber
polymer in solution, optionally purifying said solution, and admixing it with
at
least one compound containing 2 or more aziridine functional groups.
In still another one of it's aspects, the present invention relates to a self-
supported shaped article comprising said nitrite polymer composition
comprising (a) at least one carboxylated nitrite rubber polymer, that is
optionally
hydrogenated, (b) at least one compound containing 2 or more aziridine
functional groups, and (c) optionally at least one solvent optionally layered
on
or interposed between one or more supporting means.
In still another of its aspects, the present invention relates to a sealant
composition comprising said nitrite polymer composition comprising (a) at
least
one carboxylated nitrite rubber polymer, that is optionally hydrogenated, (b)
at
least one compound containing 2 or more aziridine functional groups, and (c)
optionally at least one solvent.
Brief Description of the Drawings
Fig. 1 shows the RPA 2000 Tan Delta curves @ 100 °C for Examples 1-
6.
Description of the Invention
As used throughout this specification, the term "carboxylated nitrite
polymer" or XNBR is intended to have a broad meaning and is meant to
encompass a copolymer having repeating units derived from at least one
conjugated diene, at least one alpha-beta-unsaturated nitrite, at least one at
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least one monomer having a carboxylic group and optionally further one or
more copolymerizable monomers.
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-Cs conjugated dienes are butadiene, isoprene and mixtures
thereof. The most preferred C4-Cs conjugated diene is butadiene.
The alpha-beta-unsaturated nitrite may be any known alpha-beta
unsaturated nitrite, in particular a C3-C5 alpha-beta-unsaturated nitrite.
Preferred C3-C5 alpha-beta-unsaturated nitrites are acrylonitrile,
methacrylonitrile, ethacrylonitrile and mixtures thereof. The most preferred
C3-
C5 alpha-beta-unsaturated nitrite is acrylonitrile.
The monomer having at least one carboxylic group may be any known
monomer having at least one carboxylic group being copolymerizable with the
nitrite and the diene.
Preferred monomers having at least one carboxylic group are
unsaturated carboxylic acids. Non-limiting examples of suitable unsaturated
carboxylic acids are fumaric acid, malefic acid, acrylic acid, methacrylic
acid
and mixtures thereof.
Preferably, the copolymer comprises in the range of from 40 to 85
weight percent of repeating units derived from one or more conjugated dienes,
in the range of from 15 to 60 weight percent of repeating units derived from
one or more unsaturated nitrites and in the range of from 0.1 to 15 weight
percent of repeating units derived from one or more monomers having at least
one carboxylic group. More preferably, the copolymer comprises in the range
of from 55 to 75 weight percent of repeating units derived from one or more
conjugated dienes, in the range of from 25 to 40 weight percent of repeating
units derived from one or more unsaturated nitrites and in the range of from 1
to 7 weight percent of repeating units derived from one or more monomers
having at least one carboxylic group.
Optionally, the copolymer may further comprise repeating units derived
from one or more copolymerizable monomers, such as alkyiacrylate, styrene.
Repeating units derived from one or more copolymerizable monomers will
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replace either the nitrite or the diene portion of the nitrite rubber and it
will be
apparent to the skilled in the art that the above mentioned figures will have
to
be adjusted to result in 100 weight percent.
Hydrogenated in this invention is preferably understood by more than
50 % of the residual double bonds (RDB) present in the starting nitrite
polymer/NBR being hydrogenated, preferably more than 90 % of the RDB are
hydrogenated, more preferably more than 95 % of the RDB are hydrogenated
and most preferably more than 99 % of the RDB are hydrogenated.
The present invention is not restricted to a special process for preparing
the hydrogenated carboxylated NBR. However, the HXNBR preferred in this
the invention is readily available as disclosed in WO-01/77185-A1. For
jurisdictions allowing for this procedure, WO-01/77185-A1 is incorporated
herein by reference.
The XNBR as well as the HXNBR which forms a preferred component of
the polymer compound of the invention can be characterized by standard
techniques known in the art. For example, the molecular weight distribution of
the polymer was determined by gel permeation chromatography (GPC) using a
Waters 2690 Separation Module and a Waters 410 Differential Refractometer
running Waters Millennium software version 3.05.01. Samples were dissolved
in tetrahydrofuran (THF) stabilized with 0.025% BHT. The columns used for
the determination were three sequential mixed-B gel columns from Polymer
Labs. Reference Standards used were polystyrene standards from American
Polymer Standards Corp.
The inventive polymer composition further comprises at least one
compound containing 2 or more aziridine functional groups. Compounds
containing 2 or more aziridine functional groups are known to the skilled in
the
art and any of these should be suitable for the present invention. However,
compounds of formula (I)
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R'
N
'~.N~R (I)
R'
~N~
O
in which R is hydrogen, C~ to C5o hydrocarbon that may be saturated or
unsaturated, cyclic or non-cyclic, and may further comprise heteroatoms and
each R' is independently hydroxyl, or C1 to C5o hydrocarbon that may be
saturated or unsaturated, cyclic or non-cyclic, and may further comprise
heteroatoms. Preferred are compounds with R = H or CH3 and R' = OH or
CH3. These compounds are commercially available from Bayer Inc. under the
tradenames PFAZc~ and XAMA~.
Although the inventive carboxylated nitrite polymer composition
does not require the presence of solvent, the absence of solvent does requires
extra care to prevent undesired cross-linking during mixing. Therefore, the
inventive polymer composition preferably further comprises at least one
solvent. The solvent is not critical to the result and may be any solvent that
does dissolve the, optionally hydrogenated, carboxylated nitrite polymers) and
the compounds) containing 2 or more aziridine functional groups. Suitable
examples of such solvents are ketones such as methylethyl ketone,
methylisobutyl ketone, and diisobutyl ketone; acetates such as butyl acetate;
toluene, xylene and their derivatives; or chlorinated aromatic hydrocarbons
such as monochlorobenzene. The concentration of the solution is not critical
and must be such as to allow convenient application or processing of the
solution.
The carboxylated nitrite polymer compositions of the present invention
can be cured to form substantially clear or transparent films/shaped
articles/coatings when pigments are excluded. Alternatively, optional and
preferred dyes or pigments can be readily incorporated. Colored coatings
provided in accordance with the invention provide outstanding color and
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coating physical properties for long-term weathering uses. An extensive list
of
organic and inorganic pigments suitable for adding to rubber can be found in
the current volume of the Rubber Blue Book, published by Lippincott & Peto
Publications and well known to those versed in the art of formulating
elastomers. As a brief overview, inorganic pigments such as iron oxide (rust
red), chrome oxide (green), titanium dioxide or zinc oxide (white),
ultramarine
blue, and aluminum powder (silver) are used to make opaque coatings.
The inventive carboxylated nitrite rubber composition further optionally
comprises at least one filler. The filler may be an active or an inactive
filler or a
mixture thereof. The filler may be in particular:
- 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 AI, 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;
- metal oxides, such as zinc oxide, calcium oxide, magnesium oxide
and aluminum oxide;
- metal carbonates, such as magnesium carbonate, calcium
carbonate and zinc carbonate;
- metal hydroxides, e.g. aluminum hydroxide and magnesium
hydroxide;
- 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
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from 20 to 200 m2/g, e.g. SAF, ISAF, HAF, FEF or GPF carbon
blacks;
- rubber gels, especially those based on polybutadiene,
butadiene/styrene copolymers, butadiene/acrylonitrile copolymers
and polychloroprene;
or mixtures thereof.
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 Bayer AG.
Often, use of carbon black as a filler is advantageous. Usually, carbon
black is present in the polymer composite in an amount of in the range of from
20 to 200 parts by weight, preferably 30 to 150 parts by weight, more
preferably 40 to 100 parts by weight. Further, it might be advantageous to use
a combination of carbon black and mineral filler in the inventive polymer
composite. In this combination the ratio of mineral fillers to carbon black is
usually in the range of from 0.05 to 20, preferably 0.1 to 10.
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The carboxylated nitrite rubber composition may advantageously further
comprise other natural or synthetic polymers) containing functional groups
capable of reacting with the polyaziridine compound, such as carboxylated
alpha olefin-vinyl acetate and alpha olefin-vinyl acrylate copolymers (e.g.
carboxylated EVA or EVAc). Careful blending with conventional HNBR often
reduces cost of the polymer composite without sacrificing the processability.
The amount of conventional HNBR and/or other natural or synthetic rubbers
will depend on the process condition to be applied during manufacture of
shaped articles and is readily available by few preliminary experiments.
The rubber composition according to the invention can contain further
auxiliary products for rubbers, such as antioxidants, foaming agents, anti-
aging
agents, heat stabilizers, light stabilizers, ozone stabilizers, processing
aids,
plasticizers, tackifiers, blowing agents, waxes, extenders" 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 are e.g. from 0.1 to 50 wt.%, based on rubber.
In another one of it's aspects, the present invention relates to a process
for preparing a polymer composition comprising (a) at least one hydrogenated
carboxylated nitrite rubber polymer, (b) at least one compound containing 2 or
more aziridine functional groups, and (c) at least one solvent comprising the
steps of hydrogenating at least one carboxylated nitrite rubber polymer in
solution, optionally purifying said solution, and admixing it with at least
one
compound containing 2 or more aziridine functional groups.
The XNBR must be hydrogenated to result in a partially or fully
hydrogenated nitrite polymer (HXNBR). HXNBR are preferred in the present
invention. Reduction can be effected using standard reduction techniques
known in the art. For example, homogeneous hydrogenation catalysts known
to those of skill in the art, such as Wilkinson's catalyst {(PPh3)3RhCl} and
the
like can be used.
The hydrogenation is performed in solution. The XNBR is either
provided to the reaction vessel in a dissolved state in a suitable solvent and
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hydrogenation catalyst is simply added to the vessel, which is then treated
with
hydrogen to produce the HXNBR.
Usually, Wilkinson's catalyst is used for the hydrogenation step. Details
of this process are known and e.g. can be found in CA-2,357,470.
After the hydrogenation, the HXNBR is recovered from the solution and
dried. While this a suitable step in the inventive process, the HXNBR is
preferably not recovered from solution but is instead used as is to prepare
the
nitrite polymer composition comprising (a) at least one hydrogenated
carboxylated nitrite rubber polymer, (b) at least one compound containing 2 or
more aziridine functional groups, and (c) at least one solvent comprising the
steps of hydrogenating at least one carboxylated nitrite rubber polymer in
solution, optionally purifying said solution, by simply admixing the polymer
solution with at least one compound containing 2 or more aziridine functional
groups and optionally further ingredients.
The ingredients of the final polymer composition are mixed together,
suitably at a temperature that may range from 15 °C to 40 °C.
Normally the
mixing time does not exceed one hour and a time in the range from 2 to 30
minutes is usually adequate. The mixing is suitably carried out in an internal
mixer such as a Banbury mixer, or a Haake or Brabender miniature internal
mixer. A two roll mill mixer also provides a good dispersion of the additives
within the elastomer. An extruder also provides good mixing, and permits
shorter mixing times. It is possible to carry out the mixing in two or more
stages, and the mixing can be done in different apparatus, for example one
stage in an internal mixer and one stage in an extruder. However, it should be
taken care that no unwanted pre-crosslinking (= scorch) occurs during the
mixing stage. For compounding and vulcanization see also: Encyclopedia of
Polymer Science and Engineering, Vol. 4, p. 66 et seq. (Compounding) and
Vol. 17, p. 666 et seq. (Vulcanization).
As the inventive the carboxylated nitrite rubber composition cures at
room temperatures, in particular above 0 °C, more preferred above 20
°C, the
present invention is specifically directed towards a nitrite polymer
composition
comprising (a) at least one carboxylated nitrite rubber polymer, that is
optionally
hydrogenated, (b) at least one compound containing 2 or more aziridine
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functional groups, and (c) optionally at least one solvent curable at
temperatures in the range of from 0-100 °C , in particular 15-65
°C, even more
preferred in the range of from 25-40 °C. The composition will cure
within 2 to
200 hours at room temperature. The cure can be accelerated by exposing the
composition to elevated temperatures, but this is not required.
The priming composition and/or the nitrite polymer composition can be
applied to a substrate (for example a tape substrate) by many different
methods, including solvent coating, solvent spraying, emulsion coating, low
pressure coating or other processes known to the person skilled in the art.
Suitable substrates include metal, glass, wood, stone, plastic, in particular
polyolefin films (e.g. polyethylene and polypropylene films), in particular
corona-treated polyolefin films, and paper saturated with elastomer. The
suitable coating weight is in the range from 0.1 to 5 mg/cm2, preferably from
0.2 to 1.0 mg/cm2, and more preferably from 0.3 to 0.5 mg/cm2. When the
priming layer has been applied to a substrate, it is then preferably dried.
This
drying preferably takes place at elevated temperature, under reduced pressure,
or both.
A further preferred method for the production of coated substrates is co-
extrusion coating, which is normally carried out in a coating device with a
solution of the nitrite polymer composition that is applied via a flat-
sheeting die
to a substrate that may consist of one or more polymer layers. The composite
that is thereby formed is then cured in a curing/press roll unit and smoothed.
The composite strip material is then coiled in a corresponding coiling
machine.
In another preferred embodiment, the inventive composition may
be prepared by simply mixing the ingredients by hand with a spatula or the
like
or by mechanical mixing or shaking. The final composition is typically applied
to a substrate by dipping, spraying, wiping, brushing or the like, after which
the
composition is allowed to dry for a period of time typically ranging from 30
minutes to 2 hours, preferably from 45 minutes to 1 hour. The composition is
typically applied to form a dry layer on the substrate having a thickness
ranging
from 0.1 to 5 mm, preferably from about 0.5 to 1.5 mm. The coating
compositions can be applied to substrates which have been vulcanized or to
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uncured substrates and co-cured therewith, at elevated temperatures if
necessary.
Yet another aspect of the invention is a sealant composition comprising
said nitrite polymer composition.
The sealant system is preferably a high solids system, where the
composition is usually provided with a low amounts of solvent as possible. The
sealant composition is applied on or between the materials to seal or glue.
Self-supporting shaped articles, such as tapes are especially useful in
architectural work and for insulating glass sealing. High solids systems
comprising the inventive compound are especially useful as insulation sealants
for glass windows and doors. Further areas of application include: automotive
industry, especially applications under the hood and/or at higher ambient
temperatures, building/construction, bridges, roads, transport, woodworking
and wood bonding, bookbinding, graphic industry, packaging industry,
disposable articles, laminates, shoe manufacture, end customer adhesive
applications, and in the sealant and insulating industry.
The compound of the invention remains flexible, and is especially
recommended for applications at elevated temperatures.
Furthermore, the inventive compound may be used in the manufacture
of a shaped article comprising said inventive polymer compound. Preferred
shaped articles are a seal, hose, bearing pad, stator, well head seal, valve
plate, cable sheating, wheel roller, pipe seal, in place gaskets or footwear
component prepared by injection molding technology. Furthermore, the
inventive polymer composite is very well suited for wire and cable production
tires, bumpers, wiper blades, vibration isolators, rubber mounts, rail track
pad
fasteners, helicopter rotor bearings, chassis mounts, wiper frames, gaskets,
heels, shoe soles, printing rolls, belts, fuel tanks, moldings, facias, and
other
engineered rubber goods.
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EXAMPLES
Basic chemistry
Examples 1-5
Examples 1-5 were based on a 15% (total solids) solution of Therban~
XTT"~ in methyl-ethyl-ketone.
The polyaziridine PFAZ 322 was added to the XT solution as a pure
liquid and mixed for 15 minutes. The samples were dried under vacuum at
room temperature.
Example 6 was mixed on a cold mill (20°C) for 5 minutes and then
tested. Example 1 is for comparison. Formulations are shown in Table 1
Table 1
Comp. Ex.2 Ex.3 Ex.4 Ex.5 Ex.6
Ex. 1
Therban~ XTT"'solution 1000 1000 1000 1000 1000 N/A
Therban~ XTT"~ (polymer 150 150 150 150 150 150
weight in g)
PFAZ 322 (phr) 0 0.5 2.5 5 10 0.5
PFAZ 322 (weight, g) 0 0.75 3.75 7.5 15.0 0.75
PFAZ 322 is a tri-functional azridine available from Bayer.
The solution is stable for at least 1 hour at room temperature.
The dried cured polymer are insoluble (tested in MCB, MEK THF).
Figure 1 shows the Tan delta curves for examples 1-6. Tan delta gives
an indication of the cross-linking density. A lower Tan delta indicates a
higher
elastic modulus resulting from increased cross-linking. As can be seen in
figure 1, an increase in the polyaziridine content results in an increase in
cross-
linking density. Additionally examples 2 and 6 have very similar behavior
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indicating that the cross-linking mechanism can be used using rubber mixing
methods or solution reaction.
