Note: Descriptions are shown in the official language in which they were submitted.
9 ~ 6 ~ 3 ~ 6 27980
THERMOPLASTIC E~ASTOMERI~ COMPOSITION,
PRODUCT AND METHOD OF MANUFACTURE
Background of the Invention
Rubbers and elastomers of either natural or synthetic origin
generally require vulcanization in order to obtain useful elastomeric
properties. Before vulcanization, rubbers possess tacky properties and low
strength, which make them of little utility except as rubber cements. The
optimum elastomeric properties are not attained unt:il the rubber has been
subjected to a vulcanization treatment such as by means of heating with sulfur,
sulfur compounds, peroxides, or other means. By contrast, thermoplastic
elastomers in their "green" or unvulcanized state have been developed which can
be utili~ed to make a wide variety of materials and articles having almost any
1~ desired properties. Consequently, such thermoplastic elastomers can be
readily molded into useful articles J thereby saving the time and expense of
vulcanization as well as retaining numerous properties which are not possessed
by vulcanized rubbers or elastomels. A particularly useful group of such
thermoplastic elastomers are conjugated diene/vinyl aromatic block copolymers.
It has been known in the past to extend thermoplastic elastomers with
petroleum base oils such as naphthenic, aromatic and paraffinic oils in ordar
to reduce costs and to improve the elastomeric properties of certain of the
tharmoplastic elastomers. Further, it has also been known to add fillers or
bodying agents to thermoplastic elastomers in order to reduce the cost of the
material and to add bulk and strength to the same. While a vast number of
fillers have been suggested in general terms for use in thermoplastic elasto-
mers, there is, in fact, a limited number of such materials which have been
successfully used and which are used almost universally. For example, fillers
have generally been confined to silicas, carbon blacks, numerous varieties of
china clay and whiting or calcium carbonate. However, it has been found that
these so-called conventional fillars have a tendency to haraen thermoplastic
elastomers and limit their uses in articles where flexibility flnd elasticity
are desirable. This is particularly true when large amounts of such fillers
36
are employed. Likewise, the use of excessive amounts of extender oils results
in a product which has a tendency to bleed or exude a certain amount of the oil.
While the latter is a desirable characteristic in certain uses, in other
instances it is highly undesirable.
There are also many methods of forming or molding thermoplastic
elastomers such as injection or compression molding, vacuum forming and flow
molding, and for applying a coating or sheet of thermoplastic elastomer to
woven or non-woven textiles or other substrates, such as calendering or spread-
ing the elastomer on the substrate as a hot melt. These known processes have
one or more undesirable features such as requiring extreme pressures, being
time-consuming, producing products of poor quality such as poor tear resistance
in laminated objects and, in general, undue multiplication of tha number of
steps required to produce the final product. Because of the reduced pressures
required and the reduction in the processing steps necessary, flow molding is
an attractive means of forming certain varieties of articles. In a flow mold-
ing process, the moldable material in powder, pellet or particle form~ or in
the form of a sheet is placed in a suitable mold, the mold is closed and the
moldable composition heated to a temperature just sufficient to melt and cause
flow of the moldable material into the interstices of the mold. Recently, a
particularly attractive technique of flow molding has been suggested. In
accordance with this procedure the usual flow molding process is carried out
except that rather than using radiant heat to melt and cause flow of the
moldable material, microwave energy is utilized. Heating with microwave energy
has the obvious advantage of substantially shortening the processing time but,
in addition, prevents the deleterious effects which often result from heating
for extended periods of time.
It would, therefore, be desirable to provide a moldable
thermoplastic elastomer composition which retains its property of good
flexibility, to provide an article of manufacture having this desirable
property and particularly to be able to utilize the above-described~ simplified
microwave flow molding *echnique.
3~
It is therefore an object of the present invention to overcome the
above-mentioned shortcomings of the prior art.
Another object of the present invention is to provide an improved
unvulcanized, moldable composition, a simplified method of molding and an
improved molded product.
Another object of the present invention is to provide an improved
unvulcanized, moldable composi*ion including a conjugated diene/vinyl aromatic
block copolymer.
Another and further object of the present invention is to provide an
improved flow molding technique which utilizes microwave energy as a heat
source.
~ et another object of the present invention is to provide an unvul-
canized, molded axticle of manufacture having improved flexibility.
Another object of the present invention is to provide an improved
unvulcanized, moldable thermoplastic elastomer composition containing a filler
material and an extsnder oil, an improved technique for molding such composi-
tion and an improved article of manufacture resulting therefrom.
A further ob~ject of the present invention is to provide an improved
unvulcanized, modable thermoplastic elastomer composition containing large
amounts of filler and extender oil, a simplified technique for molding such
composition and an improved article of manufacture produced thereby.
The above and other objects and advantages of the present invention
will be apparent from the following detailed description.
Summar~ of the Invention
In accordance with the present invention, it has been found that an
improved unvulcanized, moldable composition can be prepared by mixing 100 parts
by weight of a thermoplastic elastomer, at least about 20 parts by weight of an
extender oil per 100 parts by weight of the thermoplastic elastomer and at
least about 10 parts by weight of a solid, hygroscopic filler, having greater
than 1 percent by weight oE absorbed water and capable of retaining a sub-
3i~
stantial portion of such water at temperatures of at least 100C, per 100 partsby weight of the thermoplastic elastomer, the ratio of the oil to the hygro-
scopic filler being from about 0.3 to about 3. It has also been found in
accordance wi-th the present invention that an improved unvulcanized, molded
article of manufacture can be produced from the above composition, particularly
a fabric substrate having said composition bonded thereto. It has further been
found, in accordance with the present invention, that the above-mentioned
unvulcanized, moldable composition can be simply and effectively molded by
disposing the composition in a suitable mold and heating the composition by the
application of mlcrowave energy thereto while applying a pressure below about
200 psi for a time just sufficient to mel-t the composition and cause flow of the
sarne into the interstices of the mold.
The abo~e objects of the present invention and the nature of the
present invention will be clear from the following description of the preferred
embodiments.
Detailed Description of the Invention
The thermoplastic elastomers useful in practicing the present in-
vention are normally solid, block copolymers, characteristicly exhibiting high
tensile strength and elongation in their natural condition, that is, in th~ir
green or unvulcanized state. Particularly useful are linear block or radial
teleblock copolymers. More specifically, useful elastomers are radial tele-
block copolymers of butadiene/styrene. Such copolymers are described in more
detail in U.S. Patents 3,823,109; 3,326,776 and 3,959,545. These polymers are
prepared by methods well known in the art.
The butadiene/styrene copolymers, discussed above, generally contain
about 50 to 90 weight percent butadiene and from 50 to about 10 weight percent
of styrene; preferably, from about 50 to 70 weight percent butadiene and about
S0 to about 30 weight percent styrene. Copolymers particularly useful in
producing compositions in accordance with the present invention are those
having from about 60 to about 70 weight percent butadiene. When less than
about lO percent styrene is employed, the resulting copolymers do not possess
the requisite green tensile strength. On the other hand, more than 50 weight
percent of the styrene in the copolymer results in a compo3ition in which
hardness is increased at the expense of elasticity. Useful copolymers will
generally exhibit a weight average molecular weight in the range of from about
75,000 to about 500,000 but a range of about 100,000 to about 350,000 is
preferable.
It is also within the scope of the present invention to add other
polymers -to the thermoplastic elastomer in amounts up to about 150 parts by
weight of the polymer per 100 parts by weight of the elastomer. Such addi-
tional polymers are generally solid resinous polymers of a vinyl-substituted
aromatlc compound, for example, styrene, alphamethyl styrene, etc., alone or
copolymerized with a monomer such as acrylonitrile or a conjugated diene such
as butadiene. Such homopolymers and copolymers generally have densities in the
range of about 1.04 to about 1.10 gram/cc (ASTM D 792), a tensile strength in
the range of from about 5,000 to about 12,000 psi (34.5-82.7 MPa), ASTM D-638,
and a Shore A hardness ranging from about 35 to about 95 (ASTN D-2240) at about
23C.
The pr~viously mentioned thermoplastic elastomers may also have
certain amounts of the extender oil incorporated therein during their manufac-
ture. For example, the elastomers may have incorporated therein from 50 to 60
parts by weight of oil. Consequently, the amounts of added extender oil re-
ferred to herein, and specifically in the examples, are amounts in addition to
the amounts incorporated in the thermoplastic elastomer during its manufacture
and the amounts of elastomer referred to include the weight of the elastomer
including the oil added during elastomer preparation. Suitable extender oils
include those well known in the art such as naphthenic, aromatic flnd paraffinic
petroleum oils, particularly the naphthenic type.
In accordance with the present invention, the thermoplastic
elastomer composition of the present invention may have added thereto at least
~:~33~
about 10 parts by weight of extender oil per 100 parts by weight of the
thermoplastic elastomer. Preferred amounts of added extender oil include from
about 70 to about 350 parts of oil per 100 parts of thermoplastic elastomer and
ideally about 250 to about 300 parts of oil per 100 parts of thermoplastic
elastomer.
It is frequently desirable to include other additives well known in
the rubber art to the compositions of the present application. Stabilizers,
antioxidants, conventional fillers, reinforcing agents, reinforcing resins,
pigments, fragrances and the like are examples of some such additives. Speci-
fic examples of useful antioxidants and stabilizers include 2-(2'-hydroxy-5'-
methylphenyl) benzotriazole, nickel dibutyldithiocarbamate, zinc dibutyl di-
thiocarbamate, tris(nonylphenyl) phosphite, 2,6-di-t-butyl-4-methylphenol and
the like. Exemplary conventional fillers and pigments include silica, carbon
; black, titanium dioxide, iron oxide and the like. Polypropylene and poly-
styrene are examples of thermoplastic resins which function as reinforcing
agents. A butadiene/acrylonitrile elastomer is an example of an elastomer
which functions as a processing aid.
In addition to the above conventional ingredients/ it has been found,
in accordance with the prèsent invention, that an unvulcanized, moldable com-
position of a thermoplastic elastomer can be produced by adding thereto a
solid, hygroscopic filler, having greater than 1 percent by weight, and prefer-
ably greater than 4.0 percent by weight, of absorbed water and capable of
retaining a substantial portion of such water at temperatures of at least
100C, such as, bentonite clay, particularly the Western type, wood flour,
ground cork, etc., in addition to the usual amounts of the more conventional
fillers and pigments. The hygroscopic filier may be utilized in amounts in
excess of about 45 parts by weight of fillex per 100 parts of thermoplastic
elastomer (phr). These amounts do not include the usual amounts of conven-
tional fillers and pigments which can be used. Preferably, the hygroscopic
filler is utilized in amounts between about 350 and about 500 parts by weight
~..~3~3~
of filler per 100 parts by weight of thermoplastic elastomer and ideally about
400 parts filler per 100 parts thermoplastic elastomer. It has also been
found, in accordance with the present invention, that superior products can be
produced by employing a particular range of extender oil/hygroscopic filler.
Specifically, the desired weight ratios of oil to hygroscopic filler are 0.3
to 3, preferably 0.5 to 1.0 and ideally about 0.75.
The thermoplastic elastomer compositions of the present invention
may be prepared by any means well known in the art for combining such
ingredients, such as solution blending, milling~ internal batch mixing, or
continuous extrusion of a solid form of elastomer and the other ingredients.
rapid and convenient method o~ preparation comprises heating a mixture of the
components to a temperature of about 120C to about 205C, wh:ile separate
specific embodiments preferably involve stirring a mixture of the components at
about 160C to about 205C, preferably about 175C to about 205C or by heating
the mixture without stirring in a temperature range of about 125C to about
200C, preferably about 125C to about 165C. Preferably, the hygroscopic
filler is capable of retaining a substantial portion of its absorbed water at
temperatures above the melt temperature of the composition (usually about
160C) and up to the highest temperature utilized in the preparation of the
composition prior to molding.
One method of preparing a composition comprising a conjugated
di~.ne/vinyl aromatic block copolymer and extender oil involves placing a
mixture of the copolymer and extender oil in suitable container such as a flat
metal pan and heating said mixture, such as in an oven, without agitation at a
temperature which normally falls within the range corresponding to about the
melting point of the elastomer, about 120C, up to about the flash point of the
! oil, about 200C. Normally and preferably, heating is conducted within the
range of about 125C to about 165C. The composition can be fo:rmed of the
mixture within a time of several seconds to several hours but the mixture is
normally maintained at thls temperature Eor abou-c 15 minutes to several hours.
~ ~3 3~36
The -time required is dependent upon such things as the type of the elastomer
and oil employed, the temperature used and the physical size of the particles
of elastomer to be used in preparation of the composition. ~urthermore, the
time required to make a homogeneous mixture can normally be reduced by
physically mixing the rubber and -the oil prior to the heating step.
Additional additives and formula-tions can be added to the elastomer-oil blend
prior to or during the heating step. After the heating step, the composition
is normally cooled prior to use in fabricating articles.
The composition can be further trea~ed if desired or required in
any conventional mixer such as a Banbury~ (~mhart Nachinery Group, Ansonia,
Conn.) mixer or roll mill, particularly if small amounts of undissolved
elastomer remain aE~er the oven heating step or if it is desirable -to add
other ingredients prior to or during the heating step and such have not been
uniformly distributed. The additional treatment, if desired, is normally
co~ducted within the temperature range of about 75C to about ~25C,
preferably maintaining the composition below its melting point for a few
minutes up to several hours, preferably 3 to 15 minutes. A par-ticularly
useful technique is to add the hygrosGopic filler in the beginning of the
mixing cycle in order to take maximum advantage of heating time and to
prevent surface bleeding and overheating when forming the molded articles.
The resultant composition may be in the form of extruded pellets,
; cut dices, preferably as small as possible since smaller pellets provide short
heating times and better flow when utilized in flow molding. Ground pellets
may also be utilized. Where large area objects are to be made, such as in ~he
manufacture of mats, the composition may be provided in sheet form in order to
shorten the heating time and effect better flow during the molding operation.
It has been found, unexpectedly, in accordance with the present i~-
vention that by utilizing a solid hygroscopic filler, as previously discussed,
reduced time for incorporating extender oil, ease of incorporation and ex-
tremely good dispersion are attained. On the other hand, it was found ~hatwhen usirlg conventional iillers, such as calcium carbonate (whiting~ or china
P~ 9
?3~
clay, particularly at high levels, extremely long mixing times were required
and, more importantly, the resultant products were very dry, brittle and
completely unusable. Talc, par-ticularly at high loadings, also resulted in
unexpectably long mixing times and may produce unaccep-tably stiff and boardy
products. By comparisonJ products formed from the composition containing the
hygroscopic fillers exhibited very good rubberiness and other physical
properties.
It has also been found, in accordance with the present invention,
that the composition containing hygroscopic fillers responded much better to
microwave energy heating than mate,rials filled with calcium carbonate, Dixie
clays, talc, etc, The mixing difficulties with the china-type clay included
excessive stickiness in the mixer which made it impossible to conventionally
dump the mixed product.
It has also been found, in accordance with the present invention,
that mixtures in accordance with the present invention respond unexpectedly to
heating by microwave energy. It is known that the thermoplastic elastomers, in
accordance with the present invention, do not~ in and of themselves, respond
well to heating by microwave radiation. However, it has been discovered in
accordance with the present invention that the response of the thermoplastic
elastomers to microwave radiation is significantly improved by the addition of
the hygroscopic fillers. While the present invention is not intended to be
limited by any theory, it is believed that the presence and retention of signi-
ficant amounts of absorbed water by the hygroscopic filler is responsible for
such enhancement of the response of the composition to microwave radiation.
Consaquently, the hygroscopic filler should be capable of retaining a signifi-
cant amount of its abosrbed water at temperatures above the boiling point of
water, preferably above the melt temperature o~ the composition (usually
about 160C) and up to the temperature utilized in the preparation of the
composition for molding and ideally up to the highest -temperature reached in
the molding operation (generally between about 280 and abo~lt ~S0~ [138-
~L~3~36
268C~). If-the absorbed water of the hygroscopic filler is driven off during
preparation of the mixture for flow molding, the improved response to microwave
radiation does not occur, and the advantages during flow molding and of the
resultant product, set forth hereinl are not attained. In any event, tests
have shown that if the hygroscopic fillers are dried before compounding, the
receptivity to microwave radiation is significantly reduced. In addition, if
the water is driven off during flow molding surface pits and/or porosity in the
product result from the evolution of steam. Hence, the compositions of the
present invention containing the hygroscopic fillers, as defined, are not as
sensitive to overheating as iormulations containing nonhygroscopic fillers
With significant amounts of absorbed water which will not be retained during
flow molding. The above-mentioned ability to enhance the response to microwave
radiation is particularly noticeable at high concentrations ~f hygroscopic
filler.
; Undesirable evolution of steam can also be controlled by
incorporating in the mixture appropriate amounts (about 5 to about 25 parts by
weight and preferably 20 parts by weight) of a waterbinding agent like calcium
oxide, preferably in the form of an oil dispersion.
By definition, the microwave region1is that portion of the electro-
magnetic spectrum lying between the far infrared and the conventional radio
frequency portion. While the microwave region is not bounded by definition it
is commonly regarded as extending from 300,000 megacycles to 1,000 megacycles
(l mm to 30 cm in wavelength). In most areas of the world certain frequencies
have been assigned for industrial uses of microwave energy. For example~ in
*he Unlted States the assigned frequencies are 915 and 2,450 megahertz (~Hz),
in Europe assigned irequencies are 896 and 2,450 megahertz and in Japan 40 to
50 megahertz. When a material capable of absorbing microwave energy, rather \
than reflecting the same or being transparent thereto, is tr~ated with micro-
wave energy, heat i.s produced as a result of the absorption of the microwaves.
3~36
While, as previously indicated, the compositions of this invention
respond well to microwave energy, it is preferred that a polar composition be
added as a sensitizer to ~urther enhance the response to microwave energy. Not
all polar compounds have been found effective in enhancing the microwave energy
response of the compos:itions but there are a large number which have been found
so effective. For example, a material selected from among simple and polymeric
alkylene glycols and their mono- and dialkyl ethers, ethanol amines and iso-
propanol amines and their hydrocarbyl-substituted derivatives and mixtures
thereof have been found particularly useful. Exemplary compounds include
ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 1,4-butylene
glycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol,
dipropylene glycol, thiodiethylene glycol, etc., polyethylene glycols having
average molecular weights ranging from about 200 to 6,000 (commercially
available under the trademark "Carbowax" from Union Carbide Corp., ~ew York,
N.Y.) polypropylene glycols having average molecular weights from about 400 to
about 2,000; mixed poly~ethylene~-poly(propylene) glycols having average
molecular weights up to about 6,000 and containing from about 30 to about 90
weight percent e-thylene oxide; the monomethyl, monoethyl, and monobutyl ethers
o ethylene glycol, propylene glycol and diethylene glycol; -the monomethyl and
monoethyl ethers of triethylene glycols; the dimethyl and diethyl ethers o~
diethylene glycol, dipropylene glycol and trimethylene glycol; the
alkanolamines and substituted alkanolamines based on ethanol and isopropanol
such as mono-, di- and -tri-ethanol amine, ~ono-, di- and triisopropylamine,
methylethanolamine, dibutylethanolamine, phenyldiethanolamine, di~2-
ethylhexyl)e~hanolamine, dimethylisopropanolamine, dibutylisopropanolamine,
and the like; and mixtures thereof. Other polar compounds such as
acrylonitrile/butadiene copolymers, acrylonitrile/butadiene blends with
homopolymers o~ polyvinyl chloride and styrene/acrylonitrile copolymers are
also e~fective. Other materials suitable as polarizing agents include glyceryl
diacetate; di(2~hydroxyeth~1) dimethylhydantoin; ionomer resins, particularly
~ 12
3~6
with other polarizing agents and polyphenyleneoxide-polystyrene blends.
Presently preferred compounds include diethylene glycol and triethenolamine
and particularly mixtures thereof and mixtures thereof with polyethylene
glycols.
The polar agent will generally be utilized in a range of from about
0.5 to about 20 parts by weight per 100 parts by weight of thermoplastic
elastomer (phr3 and preferably about 0.75 to about 10 parts by weight per 100
parts by weight of thermoplastic elastomer.
While it has been observed that ~ome pitting and/or porosity results
when utilizing polar sensitizers in the present process, this problem can be
solved by avoiding overheating ~unnece.ssarily long periods of exposure to
microwave energy), reducing the amount of polar sensi-tizer employed and/or
adding a waterbinding agent llke calcium oxide, as previously indicated.
It has also been found, in accordance with the present invention,
that the addition of ethylene/vinyl acetata copolymer provides an unexpectedly
increased response to microwave energy. Specifically, it has been found that
by adding about 25 to about 35 parts by weight, preferably about 30 parts by
weighe~ of such polymer to 100 parts by weight of thermoplastic elastomer the
time required for microwave heating can be reduced by about one-half.
One of the distinct advantages of flow molding, utilizing microwave
energy as a heating source, is the fact that relatively inexpensive molds can
be utllized. For example, molds made of cast liquid silicone compounds may be
utilized due to the fact thet heating is rapid and pressures below about 200
psi can be utilized.
The process of flow molding in accordance with the present invention
is carried out simply by disposing the thermoplastic elastomer moldable com-
position in a suitable mold in pellet form, ground pellet form or sheet form,
applying a release sheet such as Teflon on the top of the composition, closing
the mold and exposing the closed mold to microwave ensrgy while applying a
prsssure up to about 200 psi. ~ suitable microwave unit and one which has been
3~
utilized hereinafter in the specific examples is a KN unit, Model J9 manufac-
tured by Compo Industries, Inc., Waltham, Mass. When a sheet of the moldable
thermoplastic composition is to be bonded to a woven or non-woven fabric, for
example to form a carpeting mat, this is accomplished by placing the moldable
composition in the bottom of the mold as previously mentioned, placing the
fabric, cut to size, on top of the moldable composition, placing a release
sheet on top of the fabric, closing the mold and subjecting the same to micro-
wave energy and pressure as previously described.
The following specific examples illustrate the improved
compositions, techniques of molding and articles of manufacture produced in
accord~nce with the present invention.
EXAMPLE I
Two tests were conducted utilizing two different composltions com-
prising butadiene/styrene radial teleblock copolymers. A 6 inch by 6 inch
sheet of the thermoplastic elastomer composition having a thickness of Q.170
inch was placed in a suitable mold. A carpeting of polyester was cut to the
same lateral dimensions and placed on top of the sheet of thermoplastic elas-
tomer. A release sheet was placed on top of the carpet and the mold closed.
The specimen was then subjected to high frequency microwave energy from a Compo
Industries, Inc. Model J microwave generator having a 10 kilowatt output. The
microwave generator was set at 80 percent power. The following table ssts
forth the overall composition of the polymeric elastomer composition, the
heating times necessary to attain various results and the physical appearance
of the resultant backed carpeting.
Table I
1~ 2*
Butadiene/Styrene Radial Teleblock
(70/30 Bd/St) 100 --
Butadiene/Styrene Radial Teleblock
(60/40 Bd/St) -- 100
Polystyrene 70 35
Alphamethylstyrene Polymer -- 35
Silica 30 30
Naphthenic Oil 300 250
14
3Ei6
Bentonite Clay (Western Type) 400 350
Zinc Stearate 0.~0 0.80
Antioxidant( ~ 0.70 0.70
Ethylene/Vinyl Acstate Copolymer(2) 30 --
Ethylene/Vinyl Acetate Copolymer(3) -- 30
Iron Oxide 2 2
Furnace Black, ASTM N-550 0.5 0.5
Polyethylene Glycol, Molecular Weight
About 540 3 3
Triethanolamine 6 6
943.00843.00
Good bond, but not rubber tear 4 Sec. 6 Sec.
Perfect bond with rubber tear 5-6 Sec. 7-lO Sec.
Too much penetration into carpet 8 Sec. 12 Sec.
*Ingredients are in parts by weight per 100 parts by weight of
the thermoplastic elastomer (phr).
(l) Argus Chemica} Corp., Brooklyn, N.Y., Mark(R) 1589B.
(2) Melting point about 240F tll5C).
~3) Melting point about 220F ~104C).
EXAMPLE II
In another series of tests, yet another composition comprising a
butadiene/styrene radial teleblock copolymer was utilized in two tests. In one
test ethylene/vinyl acetate copolymer having a melting point of about 240F
(115C) was added to the composition whereas in the other test this material
was not employed. The same mold, microwave generator and test procedure was
employed except that in this particular case the molding composition was placed
in the bottom of *he mold and the release sheet directly on top of the molding
composition to thereby form a mat, such as an outdoor mat without carpeting
adhered thereto. It is to be seen as a result of this test that the inclusion
of ethylene/vinyl acetate copolymer reduced the minimum heating time to less
than half of that required when the ethylene/vinyl acetate copolymer was not
employed.
Table II
Outdoor Mat Compound
3* ~*
Butadiene/Styrene Radial Teleblock
~60/40 Bd/St) 100 100
Polystyrene 100 100
Silica 50 50
~0 Naphthenic oil 250 250
Bentonite Clay 350 350
~6~3~
Zinc Stearate 0.8 0.8
Antioxidant(l) 1.0 1.0
Red Iron Oxide 2.0 2.0
Carbon Black 0.5 0.5
Triethanolamine 4 4
Polyethylene glycol~2) 3 3
E-thylene/Vinylacetate Copolymer ~ 30
861.3 891.3
~Excepting thermoplastic elastomer all ingredients are in phr.
(1) N-isopropyl-N'-phenyl-p-phenylenediamine.
(2) Molecular weight of about 540.
EXAMPLE III
Another test was conducted utilizing a bentonite clay from another
manufacturer. The composition tested and the results of this test are set
forth in Table III below.
Table III
Composition 5
Butadiene/Styrene Radial Teleblock~l) 150
Polystyrene 75
Silica 50
Bentonite Clay (350 mesh) 300
Naphthenic Oil 250
Int. Lubricant: Zinc Stearate 5
Ethylene/Vinylacetate Copolymer( ) 25
Stabilizers:
Nickel dibutyldithiocarbamate 0.5
Zinc dibutyldithiocarbamate 0.5
Antioxidant: Low Density Polyethylene( ) 1.0
Paraffin Wax 3
Dessicant(4) 20
Carbon Black 5
Sensitizers(5) 16
901 . O
Specific Gravity 1.29
300% Modulus 160
Tensile Stxength 200
Elongation 480
Shore A Hardness 43
Melt Index, Condition E 100+
*Parts by weight
(1) 60/40 Bd/St + 50 phr oil
(2) Melting point about 240F (115C)
(3) Density of 0.92 g/cc, melt index of 70 (ASTM D 1238-65,
Condition E)
.~3.~ 3~
(4) 80 wt. /~ ground CaO in high flash process oil (Desi Cal,~
Basic Chemicals, Cleveland, Ohio)
(5) Polyethylene glycol (Molecular Wt. about 540) + triethanolamine
in equal proportions.
It has also been found that ground cork is an effective hygroscopic
filler for use in the present invention. Ground cork has the additional ad-
vantage of lowering the weight of the final product.
EXAMPLE IV
Table IV below shows another series of two tests in which the same
bentonite clay as in ~xample III was utilized and a third test in which wood
floux was substituted for part of -the bentonite clay. In addition to the suit-
ability of wood flour as a hygroscopic filler, runs 7 and 8 show that ~ood
results can be obtained in flow molding the compositions of the present inven-
tion without the addition of polar sensitizers and run 6, as compared with runs
7 and 8, shows that overheating should be avoided when polar sensitizers are
added. While it has been found that wood flour is not as effective as bentonite
clay, it does in fact function in the same capacity and is useful in accordance
with the present invention.
Table IV
Composition 6* 7* 8*
Butadiene/Styrene Radial Teleblock~l)150. 150. 150.
High Density Polyethylene100. 100. 100.
Bentonite Clay (350 mesh)300. 300. 200.
Wood Flour (Douglas Fir) - - lOO.
Ethylene-Propylene-Diene Terpoly~er
Elastomer (2) 25. 25. 25.
Antioxidant?~w Density Polyethylene 1. 1. 1.
~ntioxidant 1. 1. 1.
Heat Stabilizer-Zinc Dibutyldithio-
carbamate 1. 1. 1.
Paraffin Wax 2. 2. 2.
Dessicant: CaO dispersed in oil 15. 15. 15.
Int. Lubricant: Zinc Stearate 4. 4. 4.
Napthenic Oil 100. 100. 100.
TiO2 ~pigment~ 6. 6. 6.
Cou~arone Resin 10. 10. 10.
Sensitizers:
Triethanolamine 4 4.
Polyethylene Glycol~ ) 4. - -
40 H.F. Flow-molded ln Compo Industries, Inc. Model J, 10 kw
,,,J/ 17
~"
Machine, Output setting 78.
Time, Sec. 5 5 5
Grid Plate Rectifer, D.C. Milliamperes 0.67 0.62 0.59
Radio Frequency Voltage, D.C.
Microampere~ 78 78 78
Mold Flow GoodV.Good Good
Molding Tlme Before Pitted Surface,
Sec. 7 13 15
*Parts by weight
(1) 52/48 Bd/St. + 60 phr oil
(2) Density of 0.92 g/cc, melt index of 70 ~ASTM D 1238-65,
Condition E)
(3) Argus Chemical Corp, Brooklyn, N.Y., Mark(R) 1589B
(4) Molecular Wt. about 540
EXAMPLE V
In order to illustrate the advantages of the use of bentonite clay as
a filler as opposed to whiting or calcium carbonate another series of tests was
conducted comparing these two materials. ~gain, the same microwave generator,
the same mold and the same general procedure were employed to produce a slab-
type molded sheet.
At the outset it was observed that the whiting compositions werequite difficult to mix and had a sticky, very soft composition.
The results of these tests are set forth in Table V below wherein it
is apparent that the articles molded from the compositions containing bentonite
clay, in essentially the same mesh size as the whiting, were quite flexible
whereas those produced with whiting, as an additive, were stiff and boardy. It
is also apparent that the minimum heating time required was substantially
greater for the compositions containing whiting.
Table V
Compound 9~; 10* 11* 12*
__
Butadiene/Styrene Radial Teleblock
(70/30 Bd/St)** 150 150 1;0 150
Low Dens. Polyethylene(l)100 100 100 100
Silica 50 50 50 50
Naphthenic Oil 200 200 200 200
Zinc Stearate 0.8 0.8 0.8 0.8
Stabili~ers o.7(2) o.7(2~ o.95(3) o 95(3)
Gamma-mercaptopropyltri-
methoxysilane - - 4 4
~3~
Polarizing Agents(4~ 8 8 8 8
Bentonite Clay, 325 Mesh 400 - - 400
Whiting - 400 400
909.5 909.5 913.75913.75
Mixing Observation OK Sticky, Sticky, OK
~. Soft V. Soft
Minimum Heating Time (Seconds)12 20 60 35
Melt Flow, 5Kg at 190C327 589 610 216
Shore A Hardness 63-66 39-45 58-62 72-75
10 Other Physical Properties About Equal
Molded Products Flexible Boardy Boardy Flexible
*All ingredients are in parts by weight.
**Basic copolymers included 50 phr extender oil added during
manufacture.
(1) Density of 0.92 g/cc, melt index of 70 (ASTM D 1238-65,
Condition E).
(2) 0.3 Zinc dibutyldithiocarbamate
0.5 Nickel dibutyldithiocarbamate
(3) 0.4 Zinc dibutyldithiocarbamate
0.55 Nickel dibutyldithiocarbamate
(4~ 4 Triethanolamine
4 Polyethylene glycol of about 540 molecular weight.
EXAMPLE VI
In yet another series of tests, bentonite clay was compared with
whiting in lower concentrations under essentially the same conditions as the
previous examples.
Again, it is to be observed that the products containing the benton-
ite clay were highly flexible whereas those produced from the compositions
containing whiting were stiff. In addition, it can also be observed that again
the minimum heating time for proper molding was substantially greater when
utilizing whiting as opposed to bentonite clay.
Table VI
Compound 13* 14* 15* 16*
Butadiene/Styrene Radial Telebloc~
(60/40 Bd/St) 100 100
Butadiene/Styrene Radial Teleblock
(52/48 Bd/St - 60 phr oil) - - 150 150
Alphamethylstyrene Polymer60 60 40 40
Silica 30 30 30 30
40 Naphthenlc Oil 70 70 75 75
Zinc Steflrate 0.3 0.3 0.75 0.75
Stabilizer(l) 0.5 0.5 0 5 0.5
Ethylene/Vinylacetate Copolymer(2) ~0 20 30 30
Desiccant(3) 15 15 15 15
Sensitizers~4) 3 3 6.5 6.5
Nitrile Rubber (5) - - 8
Bentonite Clay, 325 Mesh 45 - - 58
Whiting 343.8 343.8 413.75 413.75
Mixing Observation OK OK QK OK
Melt Flow, 2160g/190C48.8 102 32.8 13.9
HF Flow~Molded Tensils Slabs, 10kw M~del J Compo-Fit Machine:
Minimum Heating time 15lt 30" 20" 10"
300% Modulus, psi, 20" - - 160 220
Tensile, psi, 20" - - 400 460
Elongation, ~O~ 20" - - 660 640
Hardness, Shore A, 20" - - 62-71 72-79
Nolded Products Flexible Stiff Stiif Flexible
-~Ingredients in phr ~based on 100 parts by weight of thermoplastic
elastomer).
(1) 0.5 Tris(nonylphenyl)phosphîte.
(2) Melting point about 240F.
(3) 80 Wt. % Ground CaO in high flash process oil (Desi Cal~, Basic
Chemicals, Cleveland, Ohio).
(4) 50/50 by weight triethanolamine and polyethylene glycol of
about 540 molecular weight.
(5) Powde~ed butadiene-acrylonitrile elastomer, 50 Mooney viscosity,
NL-4, 210F, (~ycar~ 1452 P-5Ds B.F. Goodrich Chemical Co.,
Cleveland, Ohio).
~XAMPIE VII
The effect of substituting carbon black for all or part of the
hygroseopic filler was evaluated in the tests set forth in Table VII below:
Table VII
Composition 17 18 19 20
Butadiene/Styrene Radial Teleblock(l)140 140 140 140
Polystyrene 75 75 75 75
Silica 45 - 45 45
Bentonite (350 mesh) 300 300150
Carbon Black 45 150 300
Napthenic Oil 250 250250 250
Zinc Stearate 5 5 5 5
Ethylene/Vinylacetate(2) 25 25 25 25
StabiIizers:
Mickel Dibutyldithiocarba~ate0.50.5 0.5 0.5
Zinc Dibutyldithiocarbamate 0.50.5 0.5 0.5
Paraffin Wax 3 3 3 3
Sensitizers(3) 16 16 16 16
Desiccant: CaO dispersed in oil 20 20 20 20
Styrene/Butadiene(4) 15 15_ 15 15
3~36
895 895875 ~95
Calculated Specific Gravity 1.291.2~ 1.26 1.24
HFFM Time, Secs. 5 2 4 6
300% Modulus, psi 110 70 1~0
Tensile Strength, psi 150130 140 300
% Elongation 450 540300 190
Shore A Hardness 30 22 42 35
Melt Index Flow, 325 grams at 190C4.6 37.4 0.65 4.4
Nold Flow @ 2", Rating 1-5, 1 is Best 2 2 3 5
Time for Equivalent Mold Flow, Secs. 2" 2" 8" 8"
Scrub Test on White Paper, Marking Non- Non- Slight Heavy
Oil Bleedout on Brown Paper
After 3 weeks 51ightMedium Slight None
After 6 weeks Medium Heavy Medium Slight
~1) 60/40 Bd/St + 50 phr oil
(2) Molecular weight about 240
(3) Triethanolamine ~ Polyethylene glycol (Molecular Wt.
about 540) in equal portions
(4) Emulsion polymerized flt 41~F containing 50 parts carbon
black per 100 parts rubber.
It is to be observed from Table VII that, while carbon black has the
effect of reducing the bleed out of extender oil, it has a number of disadvan-
tages when compared with bentonite clay. Specifically, when 1/2 of the bentorl-
ite clay was replaced with carbon black the time necessary for molding was
increased and the melt flow of the composition was reduced. When the carbon
black replaced all of the bentonite clay the tensile, modulus and hardness
increased, as did the molding time necessary and mold flow was further reduced.
In addition, a molded sheet of the product produced heavy black marks when
scrubbed on a light colored surface.
EX~MPLE VIII
Yet another series of comparative tests was conducted as set forth in
Table VIII below:
Table VIII
Composition 21 2223 24 25 26
Butadiene/Styrene Radial
Teleblock~l) 150 )
Polystyrene 75 ) SAME
Silica 45 )
Bentonite t350 mesh) 300 )
40 Bentonite t325 mesh) 300 - - - -
36
Royal King~ Clay (Hard China) - - 300
Suprex~ Clay ~Hard China) - - - 300 - -
Gamaco~ Whiting - - - - 300
Paragon~ Clay (Sof-t China) - - - - - 300
Napthenic Oil 250
Zinc Stearate 5
Ethylene Vinylacetate
Copolymer(2) 25 )
Stabilizers:
Nickel Dibutyldithio-
carbamate 0.5)
~inc D~tyldithiocarbamate O.5) SAME
Antioxidant 0.5)
Paraffin Wax 4) 3
Styrene/B~diene( 16
Dessicant 20
Carbon Black 5
~95.5 895.5 895.5 895.5 895.5 895.5
Specific Gravity 1.29 1.29 1.29 1.29 1.29 1.29
Mixing Time, Min. 10 14 14 12 - 1~
Mixing Time, Dumping, Charact. Good Good Poor Fair Would Fair
not mix
Heating Time Grid Plate Rectifier, Max.
Secs.
3 .54 .62 .36 .38 - .36
6 .5~ .56 .36 .36 - .34
Arc Arc
12 - - .36 .36
- - - - - .35
Mold Flow Charact.
Secs.
3 Good Good No Flow No Flow- No Flow
6 Excel- Excel- (Little (Little- (Little
lent lent Flow) Flow) Flow)
Over- Over-
heat heat
12 - - Fair Fair
- - - - - Fair
Physical Properties
30% Modulus, psi 130 130 190 200 - 150
Tensile Strength,psi 200 lg0 200 220 - l70
Elongation, % 460 490 330 390 - 370
Shore A Hardness 34 39 39 34 - 32
(1) 60/40 Bd/St ~ 50 phr oil
(2) Molecular Weight about 240
(3) Argus Chemical Corp., Brooklyn, N.Y., Mark(R) 1589B
(4) Emulsion polymerized at 41F containing 50 parts carbon black
per 100 parts rubber
(5) 80 Wt. % CaO in high flash process oil (~esi Cal, Basic Chemicals,
Cleveland, Ohio)
~Trademark of company indicated on following page
`~ 22
3~
Table IX shows the comparative moisture contents of the fillers
utilized in the previous comparative examples. While the nonhygroscopic Hi Sil
233~ (PPG Industries) (Silica) and Royal King~ (H. M. Royal, Inc.) Clay (Hard
China) exhibit high initial water contents, it is obvious from the previous
examples that these materials were inferior to the hygroscopic fillers of the
present invention, due to the facts that the absorbed water is readily driven
off as soon as the temperature is above the boiling point of water, usually in
the preparation of the compositions prior to molding, and any chemically-bound
water, which is not driven off apparently does not function in the same manner,
in the present process, as does absorbed water.
Table IX
Filler ~E~ ____ % Moisture
__ __ _
1. Royal King Clay (Hard
China) H. M. Royal, Inc. 14.0
2. Western Bentonite H. M. Royal, Inc. 9.0
3. Hi Sil 233 (Silica) PPG Industries 5.3
4. Philblack N550~ (Carbon
Black) Phillips Petroleum 1.0 Max.
5. Wood Flour Wood ~lour, Inc. 5.0-8.0
6. Ground Cork Dodge Cork Company 4.0-9.0
7. Suprex~ Clay (Hard
China) J. M. Huber 1.0 Max.
8. Gamaco~ ~hiting Georgia Narble 1.0 Max.
9. Paragon~ Clay (Soft
China) J. M. Huber 1.0 Max.
Trademark of supplier indicated
Some of the advantages oE the hygroscopic fillers over nonhygroscopic
flllers, such as whiting and china clay, etc. can be summarized as follows:
Shorter mixing times.
No stickiness in the mixing chamber or on roll mills.
Shorter heating time in a high frequency field.
More suitable melt flow, i.e., higher than china clay and lower
than whiting.
Higher hardness than whiting and about the same as china clay.
Equal or slightly better stress/strain properties but considerably
better tear (hand test).
Considerably better flexibility than whiting and especially
china clay.
~hile specific materials, amounts thereof and operating procedures
have been referred to herein, numerous variations and modifications thereof
will be apparent -to one skilled in the art and the present invention is con-
sidered to include such variations and modifications.
p~
~3
