PELLICULE D'EMBALLAGE

PACKAGED ARTICLES

Abrégé anglais

INVENTORS: Theodore A Evans and William A Watts
INVENTION: PACKAGED ARTICLES
Abstract of the Disclosure
A package comprised of an article selected from
unvulcanized rubber, compounding ingredients for unvul-
canized rubber and compounding ingredients for thermo-
plastic polymers wrapped in a protective film composite
compatible with said unvulcanized rubber or thermoplastic
polymer respectively. Said film composite is comprised
of an admixture of (1) an unvulcanized elastomeric block
copolymer and (2) a thermoplastic aromatic group-containing
resin characterized by being soluble in styrene. The
invention is further directed to a method of preparing
the package and to compounding high unsaturation rubber
and thermoplastic polymers prepared by mixing said
package with high unsaturation rubber or thermoplastic
rubber respectively.

Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A packaging film composite having a
thickness in the range of about 0.5 to about 10 mils
comprised of an admixture of (1) about 80 to about
45 weight percent, based on 100 weight percent, of an
unvulcanized elastomeric block copolymer having the
general configuration A - B - A wherein each A is an
independently selected nonelastomeric monovinyl aromatic
hydrocarbon polymer block selected from styrene, .alpha.-methyl-
styrene and vinyl toluene having an average molecular
weight of about 7,000 to about 25,000 and a glass
transition temperature above about 25°C., the total
block A content being from about 20 to about 40 percent
by weight of the copolymer, and B is an elastomeric
conjugated diene polymer block selected from 1,3-butadiene
and isoprene having an average molecular weight from about
30,000 to about 100,000 and a glass transition tempera-
ture below about 10°C., said block copolymer being
further characterized by having a melt viscosity in the
range of about 0.1 to about 10 grams/10 minutes according
to ASTM No. D-1238, (2) about 20 to about 55 weight
percent of a thermoplastic resin selected from at least
one polymer of styrene, .alpha.-methylstyrene, styrene/.alpha.-methyl-
styrene, vinyl toluene, vinyl toluene/.alpha.-methylstyrene,
indene resins, alkyl phenolic resins, petroleum and coal
tar resins, said resins characterized by being soluble
in styrene and by having an intrinsic viscosity of about
0.02 to about 0.50 as determined in toluene at 30°C. and
16

(3) a sufficient amount of an anti-blocking agent.
2. The packaging film composite of claim 1
having a thickness in the range of 0.5 to 10 mils and
characterized by having an anti-block property of less
than about 10 grams, comprised of an admixture of an
unvulcanized radial or linear styrene-butadiene-styrene
elastomeric block copolymer, at least one thermoplastic
resin selected from polymers of styrene, .alpha.-methylstyrene
and styrene/.alpha.-methylstyrene and optionally containing
lubricants, fillers, pigments and stabilizers.
3. In a package of an article wrapped in a
film of an unvulcanized block copolymer, the improvement
in which said package is comprised of (A) an article
selected from at least one of unvulcanized rubber, com-
pounding ingredients for unvulcanized rubber, and
compounding ingredients for thermoplastic polymers in
(B) a packaging film composite of claim 1.
4. The package of claim 3 where said film
composite substantially encompasses said article, has
a thickness in the range of 0.5 to 10 mils, is charac-
terized by having an anti-block property less than about
10 grams, and is comprised of an admixture of an unvul-
canized radial or linear styrene-butadiene-styrene
elastomeric block copolymer, at least one thermoplastic
resin selected from polymers of styrene, .alpha.-methylstyrene
or styrene/.alpha.-methylstyrene and optionally containing
lubricants, fillers, pigments and stabilizers.
5. The package of claim 3 where said article
is an unvulcanized high unsaturation rubber tightly
17

wrapped and optionally heat sealed with said protective
film composite comprised of an admixture of said unvul-
canized elastomeric block copolymer, thermoplastic resin
and optionally containing lubricants, fillers, pigments
and stabilizers.
6. The package of claim 5 wherein said article
is selected from at least one of butadiene/styrene copoly-
mers, polybutadiene and cis-1,4-polyisoprene and where,
in said protective film composite, said block copolymer
is a radial or linear styrene-butadiene-styrene block
copolymer and said thermoplastic resin is selected from
at least one polymer of styrene, .alpha.-methylstyrene and
styrene/.alpha.-methylstyrene.
7. The package of claim 3 wherein said article
is at least one compounding ingredient for unvulcanized
rubber.
8. The package of claim 5 where said film
composite substantially encompasses said article and is
optionally heat sealed and said article is comprised of
at least one compounding ingredient for unvulcanized high
unsaturation rubber selected from resins, fillers,
accelerators, antioxidants, antiozonants, sulfur and
peroxide-type curatives and processing aids.
9. The package of claim 8 where said article
is selected from at least one of hydrocarbon resins,
fillers selected from clay, silicates and calcium
carbonate; accelerators selected from cadmium diethyl-
dithiocarbamate, tetramethyl thiuram disulfide, benzo-
thiazyl disulfide; phenolic, substituted thio ester and
18

amine-type antioxidants; aniline derivative, diamine and
thiourea anti-ozonants; sulfur-providing and peroxide
curatives; iron oxide and titanium dioxide color pigments;
carbon black, zinc oxide and hydrated silicon compound
reinforcing pigments; and polyethylene, silicon dioxide,
pumice and stearate processing aids.
10. The package of claim 7, packaged with said
film composite, optionally heat sealed, comprised of an
unvulcanized elastomeric styrene-butadiene-styrene block
copolymer, a thermoplastic resin selected from at least
one polymer of styrene, .alpha.-methylstyrene and styrene/
.alpha.-methylstyrene and optionally containing lubricants,
fillers, pigments and stabilizers.
11. The package of claim 8 where said article
is at least one compounding ingredient for thermoplastic
polymers.
12. The package of claim 11 where said article
is at least one compounding ingredient for polystyrene.
13. A compounded high unsaturation rubber
prepared by mixing a package of claim 11 wherein said
article is an unvulcanized high unsaturation rubber with
an additional package of claim 11 wherein said article is
at least one compounding ingredient for said unvulcanized
high unsaturation rubber.
14. A compounded thermoplastic polymer prepared
by mixing a thermoplastic polymer with a package of
claim 3 wherein said article is at least one compounding
ingredient for said thermoplastic polymer.
19

15. The compounded thermoplastic polymer of
claim 14 wherein said thermoplastic polymer is polystyrene.
16. A compounded high unsaturation rubber
prepared by mixing an unvulcanized high unsaturation
rubber with a package o f claim 7,
17. The compounded high unsaturation rubber of
claim 15 where said film composite has a thickness in the
range of 0.5 to 10 mils, is characterized by having an
antiblock property of less than about 10 grams, and is
comprised of said elastomeric block copolymer, thermo-
plastic resin and, optionally, containing lubricants,
fillers, pigments and stabilizers.
18. The compounded rubber of claim 17, sulfur
cured.
19. The compounded rubber of claim 17 where
said high unsaturation rubber is selected from at least
one of butadiene/styrene copolymers, polybutadiene and
cis-1,4-polyisoprene and wherein, in said film composite,
said block copolymer is a radial or linear styrene-
butadiene-styrene block copolymer and said thermoplastic
resin is selected from at least one polymer of styrene,
.alpha.-methylstyrene and styrene/.alpha.-methylstyrene.
20. The compounded rubber of claim 17 where
said packaged article is comprised of at least one
compounding ingredient for unvulcanized high unsaturation
rubber selected from resins, fillers, accelerators, anti-
oxidants, antiozonants, sulfur and peroxide-type curatives
and processing aids.

21. The compounded rubber of claim 20 where
said packaged article is selected from at least one of
hydrocarbon resins; fillers selected from clay, silicates
and calcium carbonate; accelerators selected from cadmium
diethyldithiocarbamate, tetramethyl thiuram disulfide
and benzothiazyl disulfide, phenolic, substituted thio-
ester and amine-type antioxidants; aniline derivative,
diamine and thiourea antiozonants; sulfur-providing and
peroxide curatives; iron oxide and titanium dioxide color
pigments; carbon black, zinc oxide and hydrated silicon
compound reinforcing pigments; and polyethylene, silicon
dioxide, pumice and stearate processing aids.
22. The compounded rubber of claim 21 which is
sulfur cured, where said rubber is selected from at least
one of butadiene/styrene copolymers, polybutadiene and
cis-1,4-polyisoprene and where, in said film composite,
said block copolymer is a styrene-butadiene-styrene block
copolymer and said thermoplastic resin is selected from
at least one polymer of styrene, .alpha.-methylstyrene and
styrene/.alpha.-methylstyrene.
23. In a method of preparing a package of an
article wrapped in a film of an unvulcanized block
copolymer, the improvement which comprises (A) wrapping
an article selected from at least one of unvulcanized
rubber, compounding ingredients for unvulcanized rubber,
and compounding ingredients for thermoplastic polymers
by substantially encompassing with a protective film
composite which is compatible therewith said unvulcanized
rubber or thermoplastic polymer, said film having a
21

thickness of about 0.5 to about 10 mils and comprised of
an admixture of (1) about 80 to about 45 weight percent,
based on 100 percent by weight, of an unvulcanized
elastomeric block copolymer having the general configura-
tion A - B - A wherein each A is an independently selected
nonelastomeric monovinyl aromatic hydrocarbon polymer
block selected from styrene, .alpha.-methylstyrene and vinyl
toluene having an average molecular weight of about
7,000 to about 25,000 and a glass transition temperature
above about 25°C., the total block A content being from
about 20 to about 40 percent by weight of the copolymer,
and B is an elastomeric conjugated diene polymer block
selected from 1,3-butadiene and isoprene having an average
molecular weight from about 30,000 to about 100,000
and a glass transition temperature below about 10°C.,
said block copolymer being further characterized by having
a melt viscosity in the range of about 0.1 to about
10 gms/10 min according to ASTM No. D-1238, correspondingly
(2) about 20 to about 55 weight percent of at least one
thermoplastic aromatic group-containing resin selected
from at least one polymer of styrene, .alpha.-methylstyrene,
styrene/.alpha.-methylstyrene, vinyl toluene, vinyl toluene/
.alpha.-methylstyrene, indene resins, alkyl phenolic resins and
petroleum and coal tar resins, said resins characterized
by being soluble in styrene and by having an intrinsic
viscosity in toluene at 30°C. of about 0.02 to about 0.5
and (3) a sufficient amount of an antiblocking agent
and, optionally, (B) heat sealing the film to form the
package.
22

Description

~(173570
~his invention relates to a packaging film com-
posite and to pac~aged unvulcanized rubber and packaged
compounding ingredients for various resins and plastics
therewith. The invention further relates to a method of
compounding rubber and plastics.
Heretofore~ various wrapping materials have been
used for packaging unvulcanized rubber and for packaging
compounding ingredients used for rubber and plastics. For
example~ films of polyethylene have been used for these
purposes.
However, polyethylene films ha~e many times
presented serious dispersion incompatibility difficulties
in the processing and compounding of rubber and various
plastic materials. Defective products and articles prepared
there~rom containing inherent weaknesses and inconsistent
physical properties have occurred because of discrete
polyethylene particle content.
Wrapp~ngs of styrene-butadiene-styrene block
copolymers have been suggested for wrapping bales of rubber
because of their compatability with various rubbers thereby
avoiding the serious disadvantages of polyethylene film.
An example of such a method is found in Canadian Patent
794~200.
However, the solution of one problem has been
found to create new disadvantages in the field of pac~aging
unvulcanized rubber and compounding ingredients therefor.
Such pac~aging or wrapping films are desirably required to
be as thin as reasonably possible yet maintain a substan-
tial and sufficient degree of structural integrity and

~073570
dimensional stability under stress. Film rupture is a
particular potential where large unvulcanized rubber
bales are packaged, stored against similar bales, trans-
ported and thrown about. The generally commercially
available styrene-butadiene-styrene and styrene-isoprene-
styrene block copolymers containing 40 percent or less
bound styrene are typically of insufficient mechanical
strength. Film rupture due to the actual flow of rubber or
plastic during storage can be a problem. Thus, for such
thin films~ serious difficulties, such as excessive rupture~
can arise for restraining the cold flow of packaged unvul-
canized rubber~ or the redistribution of compounding
gredients or for preserving the package integrity under
in-transit shock loads.
Therefore, it is an obiect of this invention to
provide a suitable packaging ~ilm composed of an unvulcan-
ized block copolymer composite ~or packaging unvulcanized
rubber and for packaging various compounding ingredients
therefor as well as to provide a corresponding method for
compounding tha rubber itself.
In accordance with thls invention, it has been
discovered that a packaging film composite for packaging~
or wrapping~ unvulcanized rubber and for compounding ingre-
dients therefor having a thickness in the range of about
0.5 to about 10~ preferably about 0.75 to about 5.0 mils
comprises an admixture of (1) 100 percent by weight of an
unvulcanized elastomeric block copolymer having the general
configuration A - B - A wherein each A is an indepen-
dently selected nonelastomeric monovinyl aromatic

107357~)
hydrocarbon polymer block selected from styrene, a-methyl
styrene and vinyl toluene having an a~erage molecular weight
of about 7,000 to about 25,000 and a glass transition tem-
perature above about 25C., the total block A content beîng
from about 20 to about 40 percent by weight of the copoly-
mer, and B is an elastomeric conjugated diene polymer block
selected from 1,3-~utadiene and isoprene having an average
molecular weight from about 30,000 to about 100,000 and a
glass transition temperature below about 10C., said block
copolymer being further characterized by having a melt vis-
cosity in the range of about 0.1 to about 10 grams/lO min-
utes according to ASTM No. D-1238 and, correspondingly (2)
about 20 to about 55 weight percent of at least one thermo-
plastic aromatic group-containing resin selected from at
least one polymer of styrene~ a-methyl styrene~ styrene/a-
methyl styrene, vinyl toluene, vinyl toluene/a-methyl sty-
rene, indene resins, alkyl phenolic resins, and petroleum
and coal tar resins characterized by having an intrinsic
viscosity in toluene at 30C. of about 0.02 to about 0.5.
It is understood that such film composite desir-
ably contains various typical antiblocking agents, lubri-
cants, fillers, pigments and stabilizers.
The elastomeric block copolymers useful in the
practice of this invention for the packaging of rubber or
various compounding ingredients can be of either the ra-
dial-type or of the linear type. Generally, styrene-
butadiene-styrene block copolymer is desired.
In general, the radial-type block copolymers are
.- .- .. - - . .... - . ... -. .- . : . . . ..

~073570
prepared by coupling AB block polymers with polyfunctional
agents as described in U S Patent 3,281,382.
In general, the linear block copolymer type is
prepared by any of the methods commonly used ~or block
copolymers of styrene and butadiene; for example (1) by
first preparing "living" polystyryl lithium from styrene
and an alkyl lithium and adding this to a mixture of
styrene-butadiene~ (2) by mixing either lithium metal or
a dilithium alkyl (e.g., tetramethylene dilithium), both
of which are reported to grow at both ends~ (3) by pre-
paring polystyryl lithium and sequentially polymerizing
butadiene and then styrene~ or (4) polymerizing butadiene
with polystyryl lithium and coupling with coupling agents
known to those skilled in this art.
The thermoplastic aromatic resins useful in the
practice of this invention ~or packaging rubber or various
compounding ingredients are aromatic resins desirably
selected from styrene~ a-methylstyrene, a-methylstyrene/
vinyl toluene~ a-methylstyrene/styrene, vinyl toluene,
indenes~ modified phenolics and resins ~rom petroleum
and coal-derived monomers, characterized by ha~ing an
intrinsic viscosity in toluene at 30C. of about 0.02 to
about 0.5
In general~ the aromatic resins are prepared
by conventional polymeriæation techniques, well known to
those skilled in the art.
The film composite itself is prepared by (a)
dlssolving the block polymer~ resin, protective agents~
and performance additives in a suitable solvent, (b)

1073570
casting the resultant cement onto a suitable substrate,
(c) drying the film, and (d) removing the film from the
substrate. The film composite can also be prepared by
using melt processing techniques textrusion and calen
dering).
Un~ulcanized rubbercan be advantageously packaged
according to this invention. Representative of the various
unvulcanized rubbers are natural rubber~ synthetic cis-1~4-
polyisoprene, rubbery polymers of 1,3-butadiene, butadiene-
styrene emulsion or-solution formed rubbery copolymers
and copolymers of butadiene and acrylonitrile. All of
these heretofore identified rubbers are of the high unsatu-
ration type. Namely, they contain an appreciable amount
of carbon-to-carbon double bonds therein. Although this
invention is partly directed to the packaging of the
high unsaturation-type rubbers~ the low unsaturation type
can also be packaged if desired. Representative of such
low unsaturation rubbers are butyl rubber, which is typi-
cally a copolymer containing a major amount of isobutylene
and a minor amount of isoprene~ as well as the various
ethylene/propylene copolymers and rubbery terpolymers of
ethylene/propylene and a minor amount of conjugated diene.
Various rubber compounding resins and ingredients
especially resins such as hydrocarbon resins can be
packaged according to this invention and then compounded
with the unvulcanized rubber. Representative of the various
compounding ingredients are fillers, such as clay~ sili-
cates~ calcium carbonate and the like; accelerators~ such
as, for example, cadmium diethyldithiocarbamate, tetra-

1~73570
methyl thiuram disulfide~ benzothiazyl disulfide and the
like; antioxidants, such as the well ~nown substituted
phenolic, substituted thio esters and amine type; anti-
ozonants, such as aniline derivatives, diamines and thio-
ureas; curatives, such as sulfur, sulfur providing com-
pounds and peroxides; ultraviolet agents such as substi-
tuted benzotriazoles and substituted benzophenones; color
pigments, such as iron oxide, titanium dioxides and organic
dyes; reinforcing pigments, such as carbon black, zinc
oxide and hydrated silicon compounds; and processing aids,
such as polyethylenes, silicon dioxide, pumice and stearate.
In order for the film to be useful as a packaging
composite for packaging unvulcanized rubber and various
compounding ingredients, it is necessary to mix with the
composite an anti-block agent to prevent the film from
sticking to itself. ~his additive is particularly required
where the packaged materials are stacked or "containerized"
together in order to prevent them from sticking to each
other and making them virtually impossible to separate
without actually destroying portions of the package and
material. For this purpose, various well-known anti-block
agents can be used~ representative of which are fatty acid
amides~ silicones~ soaps~ waxes~ pigments, vegetable
lecithins, etc.
The block polymer/resin composite film of the
present invention has numerous technical advantages which
will be evident from the following discussion.
Polyethylene film (PE) is generally used to
overwrap bales of rubber to simplify handling and us~.
--6--

~735~70
For most applications, the overwrapped bale is used intact;
thus the bale is charged into a banbury or another suitable
mixer and the PE film is dispersed throughout the rubber
compound during the mixing cycle. However~ in various
applications~ the dispersed PE film has caused defects to
occur in the end-product during use and is, therefore~ not a
suitable overwrap. Films of this in~ention disperse readily
in a rubber compound when mixed using conventional equipment.
Even if complete dispersion is not achieved~ defects in the
subject film ars minimized because of the inherent ability
to co-cure in the rubber matrix.
In other applications~ PE film can present prob-
lems. For the production of high impact polystyrene (HIPS),
polybutadiene tBR) or butadiene/styrene rubber (~BR) is
added directly to the styrene monomer. The overwrap must be
characterized by being soluble in styrene, and~ therefore~
PE film is not considered suitable for this application.
Thus~ HIPS film is used to overwrap SBR or BR for use in
the production of HIPS, which presents an entirely dif-
ferent problem. If the overwrapped ~BR or BR does not meet
rlgid specification limits~ it cannot suitably be used for
the manufacture of HIPS or even used for conventional pur-
pose~ because the HIPS overwrap does not disperse readily in
conventional rubber compounds. However, the composite film
of the present invention~ having an additional enhanced
structural stability~ is soluble in styrene, dispersable in
rubber compounds during conventional mixing cycles~ and
has the ability to co-cure in the rubber matrix. Therefore~
the composite of this invention overcomes the previous

1073570
deficiencies and eliminates a requirement for maintaining
an inventory of two (PE and HIPS) packaging films.
Because of the technical advantages cited above,
the film composite of this invention can readily be used
for the packaging of various compo~nding ingredients for
unvulcanized rubber and various plastics where tl) dis-
persability, (2) ability to co-cure with rubber, or (3)
styrene solubility is a requisite.
Therefore, in further accordance with this inven-
tion, a pac~aged unvulcanized rubber~ particularly a high-
unsaturation rubber as hereinbefore described and parti-
cularly a packaged unvulcanized rubber bale intended for
storage, comprises such unvulcanized rubber substantially
encompassed with an overwrap of the ~ilm composite of this
invention. Indeed, the invention is especially useful for
the storage of large unvulcanized rubber bales. The term
overwrap relates to the film as applied to the unvulcanized
rubber~ especially when in bale form. For bale wrapping,
two sheets of film are generally used. One sheet is applied
to the top of the rectangular shaped bale and the other to
its bottom. The sheets are then wrapped around the sides
of the bale and their peripheries heat sealed together.
In additional accordance with this invention, a
method of compounding rubber is provided, and the corres-
ponding compounded rubber is provided which comprises
mixing~ and the resulting admixture including the sulfur
cured admi~ture, said method comprising mixlng packaged
unvulcanized rubber, particularly hereinbefore described
- - . . . . . . .. .
. .

1~73570
high unsaturation rubber, over wrapped with the film
composite of this invention and conventional compounding
ingredients, particularly such ingredients packaged in the
film composite of this invention, optionally followed by
: 5 sulfur curing said prepared mixture of rubber, packaging
film and packaged compounds.
The practice of this invention is further illus-
trated by reference to the following examples which are
intended to be representative rather than restrictive of
the scope of the invention. Unless otherwise indicated,
all parts and percentages are by weight.
EXAMPLE I
A thermoplastic film composition consisting of
lO0 parts by weight of an unvulcanized elastomeric styrene-
butadiene-styrene bloc~ polymer (SBS) blended with 100
parts by weight thermoplastic a-methyl styrene polymer. In
the block copolymer~ said polystyrene block is a thermo-
plastic polymer portion having a molecular weight in the ~:
range of about lO~000 to about 15~000 and where said diene
20 polymer portion is a rubbery polybutadiene block having amolecular weight in the range of about 60,000 to about
70~000 and further characterized.by having a melt viscosity
of less than 1 gramJ10 minutes according to ASTM No. 1238
and containing about 30 parts by weight polystyrene bloc~
and correspondingly about 70 parts by weight polybutadiene
block. Said ~-methyl styrene resin is characterized by
having an intrinsic viscosity in toluene at 30C. of about
0.13. A small amount of modifiers, antiblock agents and
stabillzers were included in the blend. The composite or
.

10735~7V
blend ltself was prepared by dissolving the ingredients in
tetrahydrofuran at a temperature of about 50oC. The mix-
ture was then cast, dried and removed from the casting
surface to yield a 1 mil film.
A test to evaluate block, or the tendency of the
film to stick to itself, was run by placing two film
samples togèther~ face-to-face, so that a 2-inch by 2-inch~
two-ply specimen was obtained. The specimen was placed
between two metal plates in a horizontal position and a
1.6 pound per square inch pressure was placed on top of
the upper plate. The assembly was placed in a static hot
air oven at about 77C. for about 24 hours. At the end of
this time, the film was tested for resistance to bloc~ing
by measuring the force in grams to separate the films by
pulling them apart at about a 90 angle at a rate of about
20 inches per minute.
Block test results favorably indicated that less
than 10 grams of force was required to separate the two
plies of film.
In addition~ physical property tests were con-
ducted to determine structural integrity of the film,
results of which are shown in the following Table 1.
--10--

~07357C~
_ .
~ U~
m a) h
hh
~1 ~ ~ O ~ O O O O ~ O
~; ~ + ~1
O
U~ h a) C)
~1~ h O ~ O O 1~ 0 1~ 1~ rl
. t~ (~ ,-1 1~ ~ O C;~ ~
~ ~ ~I ~ ~ ~ ~ (U C)
Z1~; ~t + rl
ca .~ -
{~
~ .
O
h
~ ~ ~ O O O O O o oo o ~ " -
O H
~ ~ ~ ~ :
U~ ~
~ a)
O ~_ ~q
a~
~: h S:~ :
H 0 0 ~ O O ~ ~ h
~2;;h ~ Q ~ co ~ ~1
0
.'
+
H _~
m ~ 0 ~ :
h ~ ~1 O O O ~ O O 1
~ U~ o ~ ~ J O C~
~ ~ +

u~ r-l ~rl ~I H ~ Q~ h
o rl h ~ o ~ ~1
h _~ ~o ~ ~0 ~ O ~
P ~0 ~. u~ v
O ~O ~ O Pt O P~ ~ ~ O E~ bD O
h ~QD--~ 0~ O--~ 0~ rl E~ l H`-- 0
p.~ ~ E~ 1 ~ ~ p

~^~
1 ~ 7 3 57 0
The tensile strength (pounds per square inch)
and elongation were determined by ordinary rubber testing
techniques. The Elmendorf tear is a measure of the tear
resistance of the film in grams force at 90 per mil
thickness to cause the tear.
Note that with the thermoplastic resin addition,
all of the tensile yield, modulus, and Elmendorf tear
strength increased although the elongation decreased.
EXAMPLE II
Wrapped bales were prepared of polybutadiene in
the thermoplastic film composition of Example I (100 parts
SBS, lOO parts thermoplastic a-methyl styrene resin). The
1~ inch x 28 inch x 7 inch bales were wrapped and the film
heat sealed on the edges to form the bale envelope. One
bale was stacked on top of another and a pressure of 1.6
pounds per square inch was applied for three weeks. After
this perlod, the bales were easily separated without
adhesion or sticking tendencies. The film did not present
a rupturing problem. From the results of this test~ it
became apparent that the thermoplastic film composition had
structural integrity during application conditions as well
as indicated from the physical property data in Example I.
This test also indlcated that the film composition possessed
th~ proper dimensional stability while under stress.
EXAMPLE III
A thermoplastic film composition consisting of
lOO parts by weight of the styrene-butadiene-styrene of
Example I blended with 75 parts by weight of a-methyl
styrene thermoplastic polymer of Example I with attendant
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~735'70
additives was melt processed into a 0.75 mil film. ~he
film was tested according to the method of Example II with
similar results.
EXAMPLE IV
- 5 An experiment was conducted where films of
Example I and III were evaluated for dispersability in
unvulcanized butadiene/styrene copolymer rubber (SBR). The
dispersion evaluation was conducted by mixing one percent
- of the fllm with SBR on a heated 6 inch x 12 inch mill.
In this case 3.6 grams of film was added to 360 grams of
SBR which had been previously mill massed 30 seconds at a
mill roll gap of 0.010 to 0.015 inch and a mill roll tem-
perature of about 210F. to 212~F. The sheeted rubber mix
was continuously passed through the mill gap until all the
film was visibly dispersed into the rubber. This test is
rather severe since in actual practice the film wrapping on
a bale of rubber is typically only about 0.125 percent of
the individual bale weight. Less than 2.0 minutes mill
time was required to completely disperse the film in the
SBR.
EXAMPLE V
An experiment was then conducted to determine the
effect of the films such as those of E~amples I and III on
the integrity of cured rubber specimens, particularly where
the film is improperly dispersed in the rubber compound. A
typical SBR tire tread stock was sheeted off a mill at
0~050 inch thickness to prepare specimens for evaluation.
A ~ inch x 6 inch template was used to cut two 0.050 inch
tread stock samples and one film sample for each laminate
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~73570
to be tested. The tread stock/film/tread stock laminate,
with a 1~ inch x ~ inch Teflon (TFE), a trademark of the
E. I. du Pont de Nemours & Co.~ strip across the width, was
cured in a press for about 12 minutes at about 3250F. under
pressure. The specimens were removed immediately from the
mold and then permitted to cool to ambient temperature or
about 250C., for evaluation. Each test specimen was care-
fully inspected for voids. Then, an effort was made to
separate the tread stock plies at the film/tread stock
interface. Films prepared from a block polymer/resin
blend of this invention ef~ectively cured in place in the
typical SBR tread stock and defied separation at the film/
tread stoc~ interface, which is equivalent to the results
obtained with a control laminate of SBR stock without any
resin filmO In contradistinction, test specimens similarly
prspared of polyethylene film~SBR and of high impact poly-
styrene film/SB~ contained numerous voids and separated
readily at the film/tread stock interface.
EXAMPLE VI
An experiment was conducted to determine the
solubility of the thermoplastic resin film composite of
Example I in styrene monomer. The solubility of the film
was determined by measurlng the time requ~red to dissolve
5 grams of film in 95 grams of styrene monomer in a
4-ounce bottle at about 250C. The capped bottle was
agitated on a wrist action shaker. The experimental film
was observed to completely dissolve in 35 minutes. These
results are acceptable when compared to the typical speci-
fications of butadiene rubber dissolving time of about
-14-

1~735~0
2 hours maximum time in styrene. These results also show
that the ~ilm could be useful for packaging compounding
- ingredients such as colorants for unsaturated polyester
resin/styrene monomer compositions.
While certain representative embodiments and details
have been shown for the purpose of illustrating the inven-
tion~ it will be apparent to those skilled in this art that
various changes and modifications may be made therein with-
out departing from the spirit or scope of the invention.