Note: Descriptions are shown in the official language in which they were submitted.
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SCRATCH AND MAR RESISTANT SOFT ETHYLENE ELASTOMER
COMPOSITIONS
Field of the Invention
The invention relates to the field of soft ethylene elastomer compositions and
in
particular to soft ethylene elastomer compositions exhibiting improved scratch
and
mar resistant properties.
Background to the Invention
The manufacture of exterior automotive parts has traditionally involved hard
ethylene
elastomer compounds, which provide good impact and scratch and mar resistance
properties to the automobile exterior. These ethylene elastomers comprise a
majority
of polypropylene, a lesser amount of a rubber toughener (EPDM or EPR rubber)
and a
filler such as talc.
More recently compounds have been developed with added softness. These
compounds called "soft ethylene elastomer compounds" have a polyethylene
plastomer as the major component of the composition and polypropylene as a
minor
component. The addition of a small amount of organic peroxide, optionally with
a co-
agent, changes the melt rheology characteristics of the compound thereby
improving
thermal resistance and processing characteristics of the compound and
providing a
soft characteristic to the compound.
An example of a soft ethylene elastomer compound is disclosed in U.S. Patent
No.
6,506,842 and International Patent Application No. WO 98/32795 to Heck et al.
published July 30, 1998. U.S. Patent No.
6,506,842 and WO 98/32795 disclose a rheology-modified, substantially gel-free
ethylene elastomer composition comprising an ethylene alpha-olefin (EAO)
polymer
or EAO polymer blend and at least one high melting polymer selected from
polypropylene homopolymers and propylene/ethylene (P/E) copolymers. The
composition has at least three of the following four characteristics: a shear
thinning
index (STI) of at least 20, a melt strength (MS) of at least 1.5 times that of
the
composition without rheology modification, a solidification temperature (ST)
of at
least 1 0 C greater than that of the composition without Theology
modification, and an
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upper service temperature (UST) limit of at least 10 C greater than that of
the
composition without rheology modification.
The EAO polymer or EAO polymer blend of the ethylene elastomer is present in
an
amount of 50-90 % by weight of this component, preferably 65-85 % by weight
while
the high melting point polymer is preferably present in an amount of 50-10% by
weight, more preferably 35-15% by weight.
U.S. Patent No. 6,506,842 and WO 98/32795 also disclose a process for
preparing a
rheology-modified, substantially gel-free thermoplastic elastomer composition,
which
includes treatment with an organic peroxide, and manufacture of articles using
these
compositions.
For automotive interior and other applications that require scratch and mar
resistance,
soft ethylene elastomer compositions have been deficient due to their soft
polymeric
nature.
As a result there still remains a need to provide a soft ethylene elastomer
composition
producing compounds with improved scratch and mar resistance properties.
Summary of the Invention
According to one aspect of the invention there is provided a composition
comprising a
soft ethylene elastomer component and an effective amount of filler to impart
improved scratch and mar resistance properties to the composition while not
significantly decreasing the softness of the composition.
According to one aspect of the invention there is provided a composition
comprising a
soft ethylene elastomer component and an effective amount of filler and
compatibilizer to impart improved scratch and mar resistance properties to the
composition while not significantly decreasing the softness of the
composition.
According to another aspect of the invention there is provided a composition
comprising a soft ethylene elastomer component and an effective amount of
filler and
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silicone to impart improved scratch and mar resistance properties to the
composition
while not significantly decreasing the softness of the composition.
According to another aspect of the invention there is provided a composition
comprising a soft ethylene elastomer component and an effective amount of
filler,
silicone, and compatibalizer to impart improved scratch and mar resistance
properties
to the composition while not significantly decreasing the softness of the
composition.
According to a further aspect of the invention there is provided a composition
comprising a soft ethylene elastomer component and an effective amount of mica
and
compatibalizer to impart improved scratch and mar resistance properties to the
composition while not significantly decreasing the softness of the
composition.
According to a further aspect of the invention there is provided a composition
comprising a soft ethylene elastomer component and an effective amount of mica
and
silicone to impart improved scratch and mar resistance properties to the
composition
while not significantly decreasing the softness of the composition.
According to yet a further aspect of the invention there is provided a
composition
comprising a soft ethylene elastomer component and an effective amount of
mica,
compatibalizer and silicone to impart improved scratch and mar resistance
properties
to the composition while not significantly decreasing the softness of the
composition.
Preferred embodiments of the present invention also include a process for
preparing
the composition and an article of manufacture which has at least one component
fabricated from the composition.
The compositions of the present invention have many advantageous properties.
In
particular they are scratch and mar resistant, while not significantly
decreasing the
softness of the composition. The composition also results in the production of
articles
with low gloss.
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Detailed Description of the Invention
In a preferred embodiment, the soft ethylene elastomer component used in the
present
invention is a rheology-modified ethylene elastomer composition comprising
from
about 50 to about 95% by weight of elastomeric ethylene polymers or EAO
polymer
blend and from about 5 to about 50% by weight of a high melting polymer, based
on
the total ethylene elastomer composition.
Elastomeric ethylene polymers that are suitable for use in the ethylene
elastomer
composition include interpolymers and diene modified interpolymers.
Illustrative
polymers include ethylene/propylene (EP) copolymers, ethylene/butylene (EB)
copolymers, ethylene/octene (EO) copolymers, ethylene/alpha-olefin/diene
modified
(EAODM) interpolymers and ethylene/propylene/diene modified (EPDM)
interpolymers. More specific examples include ultra low linear density
polyethylene
(ULDPE) such as AttaneTM manufactured by The Dow Chemical Company,
homogeneously branched linear EAO copolymers such as TafinerTM manufactured by
Mitsui PetroChemicals Company Limited and ExactTM manufactured by Exxon
Chemical Company, and homogeneously branched substantially linear EAO polymers
such as the AffinityTM polymers available from The Dow Chemical Company and
Engage polymers available from DuPont Dow Elastomers L.L.C.
Preferred EAO polymer blends include homogeneously branched linear and
substantially linear ethylene copolymers with a density measured in accordance
with
ASTM D-792 of 0.85-0.92 g/cc, especially 0.85- 0.90 g/cc and a melt index or
I2
(measured in accordance with ASTM D-1238 (190 C/2.16 kg weight) of 0.01-30
preferably 0.05-10 g/10 min. These substantially linear ethylene copolymers or
interpolymers (also known as "SLEPs") are especially preferred.
In addition, the various functionalized ethylene copolymers such as ethylene
vinyl
acetate (EVA), which contain from 0.5-50 wt % units derived from vinyl
acetate, are
also suitable. When using an EVA polymer, those that have an I2 of from 0.01-
500,
preferably 0.05-50 g/10 min are preferred.
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Preferred SLEPs include Engage O polyolefin elastomers and other polymers
produced by The Dow Chemical Company and DuPont Dow Elastomers L.L.C.
The high melting polymer useful in the soft ethylene elastomer component is
preferably a homopolymer of propylene, a copolymer of propylene with an a-
olefin
such as ethylene, 1-butene, 1-hexene or 4-methyl-l-pentene. The polymer may
also be
a blend of a homopolymer and a copolymer, a nucleated homopolymer or a
nucleated
copolymer. It may further be a nucleated blend of a homopolymer and a
copolymer.
The a-olefin is preferably ethylene. The copolymer may be a random copolymer
or a
block copolymer or a blend of a random copolymer and a block copolymer. The
high
melting polymer is preferably selected from polypropylene homopolymers and
polyethylene copolymers with a melt flow rate (MFR) of (230 C and 2. 16 kg
weight)
of 0.3-60 g/10 min, preferably 0.8-40 g/10 min and more preferably 1-35 g/10
min.
A more detailed description of the preferred elastomeric ethylene polymer or
EAO
polymer blend and high melting polymer is provided in U.S. Patent No.
6,506,842 and
WO 98/32795.
The soft ethylene elastomer component is preferably a rheology-modified,
composition with low gel levels that enable the composition to maintain true
thermoplastic behaviour.
The soft ethylene elastomer component is preferably treated with a suitable
organic
peroxide in the manner described in U.S. Patent No. 6,506,842 and WO 98/32795.
Such suitable organic peroxides used for the purposes of this invention have a
half-
life of at least one hour at 120 C. Illustrative peroxides include: a series
of
vulcanizing and polymerization agents that contain a, a'-bis(t-butylperoxy)-
diisopropylbenzene and are available from Geo Specialty Chemicals under the
trade-
mark VulcupTM, a series of agents that contain dicumyl peroxide are available
from
Geo Specialty Chemicals under the trade-mark Di-cupTM, LuperoxTM peroxides
made
by Atofina, North America, or TrigonoxTM organic peroxides made by Moury
Chemical Company.
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Other suitable peroxides include dicymyl peroxide, 2,5-dimethyl-2,5-di-(t
butyl
peroxy)hexane, di-t- butylperoxide, 2,5-di(t-amyl peroxy)-2,5-dimethylhexane,
2,5-
di-(t-butylperoxy)- 2,5-diphenylhexane, bis(alpha-methylbenzyl)peroxide,
benzoyl
peroxide, t -butyl perbenzoate and bis(t-butylperoxy)-diisopropylbenzene.
The peroxide may also be used with a suitable co-agent such as Type I polar co-
agents, which are have a relatively low molecular weight. An example of this
type of
co-agent is trimethylopropane trimethacrylate (TMPTMA) sold by Sartomer under
the
name SR-350. Type II low polarity co-agent may also be useful such as 1,2-
polybutadiene sold by Sartomer under the trade-mark Ricon . The addition of co-
agent may improve the properties of the rheology-modified ethylene elastomer
compound, or reduce the amount of peroxide needed to effect the same level of
rheology modification.
The preferred ratio of peroxide to co-agent used in this invention is in the
range of
about 1:1 to about 1:4 peroxide:co-agent, but may vary depending on the
particular
application.
A more detailed description of the preferred properties of the rheology-
modified
ethylene elastomer composition is provided in U.S. Patent No. 6,506,842 and WO
98/32795. Most preferably the
composition of the present invention has a soft ethylene elastomer component
with an
STI of between 20 and 110 (calculated using a Kayeness capillary melt
rheometer in
which the shear rate is the ratio of melt viscosity at 1 sec -I to that at
1006 sec 1), a MS
of > 1.5, a ST of between 75 and 145 C (calculated using differential
scanning
calorimetry to measure the crystallization temperature of the first peak on
cool-down)
and a UST of between 50 and 160 C (calculated using thermal mechanical
analysis to
determine the temperature at which the penetration probe penetrates
600'microns into
the sample with the temperature being ramped from room temperature at 3 C per
minute).
The soft ethylene elastomer component is combined with an effective amount of
filler
to improve the scratch and mar resistant properties of the soft ethylene
elastomer
component. The filler may be a platy filler, such as mica, talc or clay.
Alternatively,
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the soft ethylene elastomer component may be combined with a hard, spherical,
or
elongated filler such as activated alumina.
Most preferably, the soft ethylene elastomer component is combined with an
effective
amount of the filler mica. The mica is preferably a wet-ground mica of 325
mesh.
Preferably a muscovite mica is used or alternatively a phlogophite mica.
The filler is present in an amount of from about 1 to about 20 % by weight of
the total
composition, preferably between from about 2 to about 15% by weight, more
preferably from about 3 to about 12% by weight, and further more preferably
from
about 4 to about 10% by weight.
The filler may also be combined with a compatibalizer to obtain improved
scratch and
mar resistant properties.
The addition of the filler and compatibalizer into the composition of the
present
invention may be by direct addition to the soft ethylene elastomer component
during
compound manufacture or preferably by addition through a pre-made masterbatch.
If
a masterbatch is used, it is preferably comprised of filler, compatibalizer
and base
resin in which the compatibalizer comprises from about 1 to about 20% of the
total
masterbatch composition, while the filler comprises from about 10 to about 90%
of
the total masterbatch composition. Preferably, the masterbatch comprises from
about
to about 15% compatibalizer and from about 30 to about 60% filler.
The compatiblizer is preferably a functionalised polyolefin comprising maleic
anhydride grafted Engage or equivalent metallocene polyethylene plastomer,
maleic
anhydride grafted ethylene propylene copolymer, maleic anhydride grafted
ethylene
propylene diene monomer, maleic anhydride grafted linear low density
polyethylene,
maleic anhydride grafted very low density polyethylene or maleic anhydride
grafted
polypropylene. The compatibalizer acts as a coupling agent in so far as it
helps to
increase the adhesion of the filler to the soft ethylene elastomer component.
The
compatibalizer has a polar portion that binds to the filler and a non-polar
portion is
compatible with the soft ethylene elastomer component to ensure effective
adhesion
between the filler and the soft ethylene elastomer component. In a preferred
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composition of the present invention, the compatibalizer comprises from about
0.1%
to about 10%, preferably from about 0.25% to about 7% by weight of the
composition.
The base resin in the masterbatch is preferably a carrier resin such as an
Engage@
polyolefin plastomer, linear low density polyethylene, very low density
polyethylene
or ethylene propylene copolymer. Where the base resin in the masterbatch is a
functionalised resin such as ethylene vinyl acetate, or a copolymer of
ethylene and
methylacrylic acid or acrylic acid, the functionalised resin may behave in
part as a
compatibalizer. The base resin in the masterbatch is typically compatible with
the
elastomeric ethylene polymer of the composition.
Preferably the melt viscosity of the compatibalizer and the base resin that is
used in
the masterbatch should be similar or somewhat lower than the melt viscosity of
the
soft ethylene elastomer component to ensure good dispersion.
An example of a mica masterbatch suitable for use in the composition of the
present
invention would comprise 12% maleic anhydride functionalized resin as a
coupling
agent (compatibalizer), 30% mica, and a suitable polyethylene carrier resin.
The composition of the present invention and the masterbatch may also comprise
additional additives without deviating from the invention as claimed. These
additives
may include EAOs that have not been rheology modified, process oils,
plasticizers,
specialty additives and pigments. The specialty additives include flame
retardants;
antioxidants; surface tension modifiers; anti- block agents; lubricants;
antimicrobial
agents such as organometallics, isothtazolones, organosulfurs and mercaptans;
antioxidants such as phenolics, secondary amines, phophites and thioesters;
antistatic
agents such as quaternary ammonium compounds, amines, and ethoxylated,
propoxylated or glycerol compounds; hydrolytic stabilizers; lubricants such as
fatty
acids, fatty alcohols, esters, fatty amides, metallic stearates, paraffinic
and
microcrystalline waxes, silicones and orthophosphoric acid esters; mold
release agents
such as fine-particle or powdered solids, soaps, waxes, silicones, polyglycols
and
complex esters such as trimethylol propane tristearate or pentaerythritol
tetrastearate;
pigments, dyes and colorants; plasticizers such as esters of dibasic acids (or
their
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anhydrides) with monohydric alcohols such as o-phthalates, adipates and
benzoates;
heat stabilizers such as organotin mercaptides, an octyl ester of thioglycolic
acid and a
barium or cadmium carboxylate; ultraviolet light stabilizers such as a
hindered amine,
an o-hydroxy-phenylbenzotriazole, a 2- hydroxy,4-allcoxyenzophenone, a
salicylate, a
cynoacrylate, a nickel chelate and a benzylidene malonate and oxalanilide; and
zeolites, molecular sieves and other known deodorizers. A preferred hindered
phenolic antioxidant is IrganoxTM 1076 antioxidant, available from Ciba-Geigy
Corp.
Additional fillers may also be useful in conjunction with the composition of
the
present invention. Such fillers may include carbon black, glass, metal
carbonates such
as calcium carbonate, metal sulfates such as calcium sulfate, talc, clay or
graphite
fibers. These fillers may impart further scratch and mar resistance properties
to the
composition.
The additional additives, if used, are typically present in an amount of less
than about
45 %, based on the total composition weight. The amount is advantageously from
about 0.00 1 to about 20 %, preferably from about 0.01 to about 15 % and more
preferably from about 0.1 to about 10%.
Most preferably a silicone additive is added to the composition to provide
enhanced
scratch and mar resistant properties. Silicone is added in an amount of 0.10
to 2.50%,
preferably 0.20 to 1.00%, most preferably 0.25 to 0.6%. The amount of silicone
additive that is added to the composition will be less than the amount of
filler in the
composition.
The amount of silicone to be added to the composition will depend in part on
the fluid
viscosity of the silicone to be added. The fluid viscosity is a standard
viscosity
measured at 25 C. Preferably higher molecular weight silicones, such as
polydimethylsiloxane, may be added with a fluid viscosity of at least 1,000
CSt,
preferably at least 10,000 CSt. The silicone maybe added as a masterbatch or
injected as a pure liquid. If in masterbatch form the silicone will typically
comprise
between about 10% and about 50% of the masterbatch depending on the fluid
viscosity of the silicone.
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The silicone may be added to the feed throat of the extruder. However, the
silicone,
which acts as a lubricant in the composition, is preferably added downstream
in the
extruder to the molten soft ethylene elastomer component. ,
Where filler is added as a masterbatch, both the masterbatch and the soft
ethylene
elastomer component may be added to the feed throat of the extruder at the
same time.
The soft ethylene elastomer component may also be added in its individual
components along with the masterbatch. Alternatively, the masterbatch may be
added
directly to the molten soft ethylene elastomer component after it has melted.
Where filler is added to the soft ethylene elastomer component in its pure
form the
filler is preferably added after or at least at the same time as the
compatibalizer has
already been added to the soft ethylene elastomer component although other
sequences are possible.
Addition to the feed throat will require that the feed throat be kept at a
temperature
cold enough to prevent bridging of components in the feed throat. Subsequent
processing of the composition occurs by mixing at a temperature of from about
180 to
220 C, preferably from about 190 to about 210 C.
At the end of the extrusion process, the molten polymer extrudate must be
cooled to a
low temperature before being solidified so that it can be cut into pellets. If
the molten
polymer extrudate is cut underwater, the water temperature should be
maintained at or
below about 30 C, preferably at or below 15 C.
It will be apparent to those skilled in the art that many types of mixing
equipment may
be used to make the composition of the present invention including a Farrel
Continuous Mixer, single screw or twin screw extruder and buss kneader.
The compositions of the present invention may be formed into articles of
manufacture
such as parts, sheets, or other forms using any one of a number of
conventional
procedures for processing elastomer compositions. The compositions can also be
drawn into films, multi-layer laminates or extruded sheets, compounded with
one or
more organic or inorganic substances, injection-molded into articles such as
knobs,
handles for appliances or consumer goods, used for profile-extruded articles,
or used
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for coated fabrics or other film and sheet applications. The compositions may
be
useful in the manufacture of automobile interior parts, automobile exterior
parts,
consumer goods with soft touch grips and consumer appliances with soft touch
surfaces. Other applications may also be possible and are within the knowledge
of the
person skilled in the art.
The compositions of the present invention have surprisingly improved scratch
and
mar resistant properties relative to other soft ethylene elastomer
compositions. The
compositions are also useful in the manufacture of articles with low gloss.
The following examples illustrate, but do not limit the present invention.
Example 1:
All compositions used were made on a twin-screw extruder (38:1 L/D or 50:1
L/D) at
a processing temperature of between 190 and 210 C. The throughput was about
150
lbs/hr at a screw speed of 350 RPM. The melt was pelletized using an
underwater
pelletizer with the cutting water kept cold at about 11-14 C. The mica
masterbatch
was added to the feed throat. The silicone masterbatch was added part way down
the
extruder as a side-feed into the molten polymer.
The compositions were formed into embossed sheets using conventional
processing
means. The embossed sheets had a deep hair cell grain and were pigmented
black.
The embossed side of each of the sheets was tested for the following
properties,
which are set out in Table 2:
(a) shore A hardness of sheet stock under constant load (1 second) was tested
according to ASTM D 2240-00;
(b) % gloss at 60 deg angle using a glossmeter was tested according to ASTM D
523;
(c) degree of scratching was tested using the 5-finger scratch test described
in
Ford FLTM BN at 108-13, where a measurement of 5 indicates the most
severe scratch line and a measurement of 1 indicates that no visible scratch
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lines can be detected on the sheet. Scratch and mar was tested using 1, 2, 3,
6
and 7 Newtons of force.
Of the sheets tested, the "Control" sample is the unmodified composition-
called
Advantech 8800 ATM, commercially available from DuPont. This composition
comprises the following components:
(a) 74.53% by weight of a mixture of low density Engage resins
comprising as the primary component Engage 8100 and as the
secondary component Engage 8842;
(b) 22.97% by weight of polypropylene homopolymer resin with a melt
flow rate at 230 C, using a 2.1 kg weight, of 12 grams/10 minutes;
(c) 2.5 % by weight of Vul-Cup 20P (Geo Specialty Chemicals)
comprising
20% organic peroxide/5% silica/75% polypropylene
Sample A comprised a mica masterbatch. The composition of the masterbatch was:
12% maleic anhydride functionalised resin as a coupling agent
(compatibalizer), 30%
mica, and Engage 8100. The mica comprised 7 % by weight of the final
composition.
Samples B, C and D comprised a mica masterbatch as well as a silicone
masterbatch
additive. The composition of the samples A, B, C, and D are set out below.
Table 1: Composition of Samples
Sample Base Component Additive % wt additive in final
composition
Control Advantech 8800 ATM None ---
A Advantech 8800 ATM mica masterbatch 7 % mica
B Advantech 8800 ATM mica masterbatch 7 % mica, 0.25 %
and silicone silicone
masterbatch
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Sample Base Component Additive % wt additive in final
composition
C Advantech 8800 ATM mica masterbatch 7 % mica, 0.50 %
and silicone silicone
masterbatch
D Advantech 8800 ATM mica masterbatch 7% mica, 0.875 %
and silicone silicone
masterbatch
Table 2: Comparison of properties of the embossed side of extruded sheet stock
Sample Scratch Scratch Scratch Scratch Scratch Gloss Shore A
Test 7N Test 6N Test 3N Test 2N Test 1N 600 Value
Control 3 3 2 1 1 1.2 90.5
A 1 1 1 1 1 0.8 92.5
B 2 1 1 1 1 0.9-1.2 92.6-93.2
C 1 1 1 1 1 0.9-1.1 93.0-93.7
D 1 1 1 1 1 1.0 93.5
Sample A, had the best combined scratch and mar resistance and gloss
properties.
The softness of the composition was not significantly decreased with the
addition of
the mica masterbatch in the composition. The addition of silicone also
resulted in a
composition with improved scratch-and-mar resistance, while maintaining the
softness of the composition. Each of the compositions tested, produced a sheet
with
low gloss.
Example 2:
A sheet comprising Advantech 8800 ATM base resin, 7 % mica and 0.50 % silicone
(sample C) was thermoformed into an article, by preheating and forming the
sheet
into a shape. The embossed side of the sheet was tested against the
thermoformed
article for scratch and mar resistance using the 5-finger scratch test as
described in
Ford FLTM BN at 108-13. The % gloss of the embossed side of the sheet was also
tested against the thermoformed article at a 60 degree angle using a
glossmeter, tested
according to ASTM D 523.
Thermoforming was performed using a Sencorp thermoform machine by placing the
sheet between a top and bottom platen. The temperature of the top platen was
507 F
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and the temperature of the bottom platen was 580 F. The sheet was pre-heated
for 80-
120 seconds and then thermoformed for 18 seconds.
Table 3: Comparison of Properties of Thermoformed and Non-Thermoformed
Sheet
Sample Scratch Scratch Scratch Test Gloss 60
Test 10N Test 7N 5N
Control 4 3 2 1.2
Sample C 2-3 1 1 0.7-0.8
Control 4 3 2 1.6
Thermoformed
Sample C 1-2 1 1 1.3-1.4
Thermoformed
The thermoformed sheet had the same scratch and mar resistance as the non-
thermoformed sheet, when tested under a force of 5 and 7 Newtons, and superior
scratch and mar resistance properties to the control sheets. At 10 Newtons the
thermoformed sheet showed improved scratch and mar resistance over the non-
thermoformed sheet and superior results to the control sheets. The gloss of
the
thermoformed sheet increased slightly when compared with the gloss of the non-
thermoformed sheet, but was less than the gloss of the thermoformed control
sheet,
which did not comprise mica and silicone.
Example 3
Low viscosity injection molded compositions were prepared on a twin-screw
extruder
(50:1 L/D) at a temperature of between 190 and 210 C. The throughput was
about
150 lbs/hour at a screw speed of 350 rpm. The melt was pelletized using an
underwater pelletizer having a water temperature of about 10-14 C. Mica
masterbatch was added to the composition by addition at the feed throat.
Silicone
masterbatch was also added to the composition by addition part way down the
extruder as a side-feed into the molten polymer.
The compositions were injection molded into air-bag doors at a melt
temperature of
198-216 C using a screw speed of 50 rpm and a mold temperature of about 27
C.
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The air bag doors were tested for scratch and mar resistance using the 5 -
finger
scratch test described in Ford FLTM BN 108-13, where a rating of 5 indicates
the
most severe scratch line and a measurement of 1 indicates that no visible
scratch lines
can be observed. Scratch and mar was tested using a 7 Newton force.
The "control" composition was comprised of the following components:
a) 74.25 % by weight of Engage resin 8130;
b) 24 % by weight of polypropylene homopolymer (nucleated and comprising
antistatic properties) having a melt flow rate of 12 grams/10 minute at 230
C,
using a 2.1 kg weight; and,
c) 1.75 % by weight of Vul-Cup 20P (Geo Speciality Chemicals) masterbatch
comprising 20 % organic peroxide/5% silica/75% polypropylene.
Sample A comprised the "control" composition and 6.8 % weight mica and 0.5 %
weight silicone in the final composition. The composition of the mica
masterbatch
used in Sample A comprised 12 % weight maleic anhydride functionalized resin
as a
coupling agent (compatibilizer), 30 % weight mica, and Engage 8100.
Table 4: Comparison of the scratch and mar properties of the airbag doors
Scratch Test 7N Scratch Test 7N (Sample A)
(Control)
Smooth Side 4 2
Grain Side 3 2
The addition of mica and silicone resulted in a significant improvement of the
scratch
and mar properties compared to the "control" sample.
Various embodiments of the present invention having been thus described in
detail by
way of example, variations and modifications will be apparent to those skilled
in the
art. The invention includes all such variations and modifications as fall
within the
scope of the appended claims.
