High-strength breathable films of block copolymer lattices

The invention is a film having a discontinuous phase of open and closed cells and a continuous organic phase comprising: PA1 (a) one or more block copolymer(s) corresponding to the Formula I: EQU A--B--X.sub.m --(B--A).sub.n (I) wherein each A is a polymer block derived comprising one or more monovinylidene aromatic monomers, each B is a polymer block derived from one or more conjugated dienes, X is the remnant of a multifunctional coupling agent, m is 0 or 1, and n is an integer from 1 to 5, each A polymer block has a weight average molecular weight from 4,000 to 20,000 Daltons, each B polymer block has a weight average molecular weight from 20,000 to 100,000 Daltons, wherein the block copolymers are optionally hydrogenated; and PA1 (b) optionally, an extender which is compatible with the B polymer block, and wherein the organic phase contains from about 5 to about 30 percent by weight of units derived from monovinylidene aromatic monomers and the effective phase volume of the A polymer block in the organic phase is from about 5 to about 20 percent. Also claimed is a process for the preparation of such articles.

BACKGROUND OF THE INVENTION 
The present invention relates to high-strength open cell films prepared 
from aqueous dispersions of block copolymers of vinyl aromatic monomers 
and conjugated dienes, wherein the conjugated diene block may optionally 
be hydrogenated. The invention also relates to a process for the 
preparation of such high strength open cell films. 
High strength solid films prepared from dispersions of block copolymers of 
vinyl aromatic monomers and conjugated dienes, wherein the conjugated 
diene block may optionally be hydrogenated, are disclosed in commonly 
assigned patent applications, WO 94/15997 (equivalent to Ser. No. 170,625, 
filed Dec. 20, 1993) and WO 96-15189 (equivalent to co pending application 
Ser. No. 339,862, filed Nov. 15, 1994). The disclosed films are monolithic 
and are not suitable for applications wherein the rapid transport of gas 
or moisture through the film is required. 
Accordingly, there remains a need to provide films prepared from aqueous 
dispersions of block copolymers having high strength properties and the 
ability to rapidly transport gas or moisture through the film. In 
addition, it would be desirable to provide a process capable of preparing 
strong open cell films having the ability to rapidly transport gas or 
moisture through the film from aqueous lattices of block copolymers that 
use relatively short times and mild temperature conditions for the 
annealing step to thereby avoid significant polymer degradation. It would 
be desirable to provide a process for the preparation of thin elastomeric 
articles having the ability to rapidly transport gas or moisture by film 
deposition from a block copolymer latex that avoids the use of additives. 
What is needed, are stable aqueous dispersions of block copolymers which 
form good films by deposition, wherein the films anneal rapidly at 
moderate temperatures and demonstrate high tensile strengths and rapid 
transport of gas and moisture. For many uses, thin elastomeric films must 
demonstrate resistance to degradation by ozone. What is needed are stable 
aqueous dispersions of block copolymers which form ozone-resistant films, 
and such ozone-resistant films. 
SUMMARY OF THE INVENTION 
Accordingly, the present invention comprises a film having a discontinuous 
phase of open and closed cells and a continuous organic phase comprising: 
(a) one or more block copolymer(s) corresponding to Formula I: 
EQU A--B--X.sub.m (B--A).sub.n (I) 
wherein each A is a polymer block derived from one or more monovinylidene 
aromatic monomers, each B is a polymer block derived from one or more 
conjugated dienes, X is the remnant of a multifunctional coupling agent, m 
is 0 or 1, and n is an integer from 1 to 5, each A polymer block has a 
weight average molecular weight from 4,000 to 20,000 Daltons, each B 
polymer block has a weight average molecular weight from 20,000 to 100,000 
Daltons, wherein the block copolymers are optionally hydrogenated such 
that a portion of the residual olefinic unsaturation derived from the 
conjugated dienes is eliminated and the hydrogenated conjugated diene 
portion contains sufficient branching such that the block copolymer is 
elastomeric; and 
(b) optionally, an extender which is compatible with the B polymer block, 
wherein the organic phase contains from about 5 to about 30 percent by 
weight of units derived from monovinylidene aromatic monomers and the 
effective phase volume of the A polymer block in the organic phase is from 
about 5 to about 20 percent. 
In another embodiment, the invention is a process for preparing a film 
having a continuous organic phase and a discontinuous phase of open and 
closed cells which process comprises: 
(1) forming an aqueous dispersion which comprises an organic phase as 
described hereinbefore, a surfactant in sufficient amount to emulsify the 
organic phase in water; and water, 
(2) frothing the dispersion such that gas bubbles are entrained throughout 
the dispersion; 
(3) depositing a coating of the frothed aqueous dispersion on a surface and 
drying the coating to form a film, 
(4) annealing the film at about 30.degree. C. to about 120.degree. C. for 1 
to 60 minutes; and 
(5) removing the film from the surface. 
Such block copolymers readily form thin films, having open and closed 
cells, by deposition onto solid surfaces from an aqueous dispersion. Such 
films may be dried to form film articles having open and closed cells 
therein, high annealed strength properties using short annealing times and 
mild annealing temperatures and good gas and vapor transmission 
properties. Examples of such articles include breathable gloves, soft 
wound dressings and other thin elastomeric articles. If a tackifier and, 
optionally, other formulants known to one skilled in the art are combined 
with the block copolymer, films having adhesive properties may also be 
prepared. Such films may be deposited onto a thin, flexible substrate for 
use as pressure sensitive tapes, packaging tapes, masking tapes, labels, 
etc. 
DETAILED DESCRIPTION OF THE INVENTION 
The films of the invention contain open and closed cells as a discontinuous 
phase in the continuous organic phase. These cells are in essence voids in 
the polymer film. The size and relative volume percentage of the cells is 
dependent on the processing techniques used and can be controlled by the 
choice of processing techniques. The size and volume percentage of the 
cells can be any size or volume, provided the organic phase is the 
continuous phase and the desired gas or vapor transmission and strength 
properties are achieved. Preferably, the average cross-section of the 
cells is about 0.01 mm or greater, more preferably, about 0.05 mm or 
greater and most preferably, about 0.1 mm or greater. Preferably, the 
average cross-section of the cells is about 20 mm or less, more 
preferably, about 10 mm or less and most preferably, about 5 mm or less. 
Preferably, the volume percentage of the cells is about 20 percent or 
greater of the total film or article, more preferably, about 30 percent or 
greater and most preferably, about 40 percent or greater. Preferably, the 
volume percentage of the cells is about 80 percent or less of the total 
film or article, more preferably, about 70 percent or less and most 
preferably, about 60 percent or less. Preferably, the films of the 
invention have a density of about 0.2 g/cc or greater, more preferably, 
about 0.3 g/cc or greater and most preferably, about 0.4 g/cc or greater. 
Preferably, the films of the invention have a density of about 3 g/cc or 
less, more preferably, about 2 g/cc or less and most preferably, about 1.5 
g/cc or less. Typically, the cells are filled with air or the gas which is 
used to create the cells during the frothing process. Examples of such 
gases includes carbon dioxide, nitrogen, argon, air, and the like. 
It has been discovered that by careful selection of the block copolymer and 
the total volume of the monovinylidene aromatic monomer phase, stable 
aqueous dispersions can be prepared which form strong free-standing films 
having open and closed cells therein upon drying at relatively low 
temperatures. In selecting appropriate block copolymers, the weight 
average molecular weight of the monovinylidene aromatic monomer block must 
be within the limits defined herein. If the chain length is too high, the 
annealing time required to form a high-strength film becomes unacceptably 
long. If the endblock length is too low, the films prepared do not exhibit 
acceptable tensile strengths. The total volume of the monovinylidene 
aromatic monomer (A block) in the organic phase is important in that, if 
the volume of the monovinylidene aromatic monomer phase is too high, 
stable dispersions cannot be formed using a relatively low amount of 
surfactants. If the A block phase volume is too low, the films prepared 
from the block copolymers will not exhibit the required tensile strengths. 
Both linear and radial block copolymers are suitably employed in the 
invention. Most preferably, however, the block copolymers are sequentially 
polymerized triblock copolymers, i.e., in Formula (I), n is equal to 1, 
and m is equal to 0. 
The conjugated diene portion of the block copolymer may be optionally 
hydrogenated to remove the residual unsaturation. The conjugated diene may 
be partially or fully hydrogenated. Preferably, a significant portion of 
the olefinic unsaturation is eliminated by hydrogenation while a 
significant portion of the aromatic unsaturation derived from the 
monovinylidene aromatic monomers is retained. More preferably, about 99 
mole percent or greater of the olefinic unsaturation is eliminated by 
hydrogenation. More preferably, about 90 mole percent or greater of the 
aromatic unsaturation is retained. Even more preferably, about 95 mole 
percent or greater of the aromatic unsaturation is retained, and most 
preferably, about 99 mole percent or greater of the aromatic unsaturation 
is retained. 
In hydrogenated block copolymers the diene block must have sufficient 
branching to prevent formation of crystalline domains to retain the 
elastomeric properties of the block copolymer. As used herein, "branching" 
means after polymerization, lower alkyl or alkenyl substituents are 
pendant from the conjugated diene portion of the block copolymer. For 
example, if isoprene is used to prepare the desired diene block, methyl 
groups are pendant from the chain. Where a straight-chain conjugated 
diene, such as butadiene, is used there must be a sufficient amount of 
1,2-addition to prevent formation of crystalline domains. 1,2-addition 
results when the polymerization occurs through one olefinic bond rather 
than through both olefinic bonds. When polymerization occurs through one 
olefinic bond, an unsaturated group is pendant from the polymer chain. 
Where a straight-chain conjugated diene is used, the 1,2-addition is 
preferably, about 25 mole percent or greater, more preferably, about 30 
mole percent or greater and most preferably, about 35 mole percent or 
greater. If too much branching is present, the resultant polymer is no 
longer elastomeric. Preferably, the 1,2-addition is about 60 percent or 
less and more preferably, about 50 percent or less. The amount of 
1,2-addition for butadiene can be increased by the use of a polar 
co-solvent in the polymerization. Preferably, only a portion of the 
solvent used is polar. A preferred co-solvent for this purpose is 
tetrahydrofuran. "Derived from monomers," as used herein, means that the 
polymer block(s) referred to comprise the residue of the monomers referred 
to in the polymer block. Residue refers to the portion of the monomer 
which remains in the polymer block after polymerization. 
Preferred monovinylidene aromatic and conjugated diene monomers useful 
herein are disclosed in co pending application Ser. No. 469,184 filed, 
Jun. 5, 1995, at page 6, lines 26 to 35 and commonly assigned WO 94/15997 
at page 3, lines 31 to 36, published Jul. 21, 1994 (relevant portions 
incorporated herein by reference). Preferably, the amount of 
monovinylidene aromatic monomer in the organic phase is about 5 percent by 
weight or greater, more preferably, about 6 percent by weight or greater 
and most preferably, about 10 percent by weight or greater. Preferably, 
the amount of monovinylidene aromatic monomer in the organic phase is 
about 30 percent by weight or less, more preferably, about 25 percent by 
weight or less and most preferably, about 20 percent by weight or less. 
Preferably, the monovinylidene aromatic monomer block has a weight average 
molecular weight of about 4,000 Daltons or more, more preferably, about 
5,000 Daltons or more, and most preferably, about 8,000 Daltons or more. 
Preferably, the monovinylidene aromatic monomer block has a weight average 
molecular weight of about 20,000 Daltons or less and more preferably, 
about 15,000 Daltons or less. Preferably, each conjugated diene block (B) 
has a weight average molecular weight of about 15,000 Daltons or greater, 
more preferably about 20,000 Daltons or greater, even more preferably, 
about 25,000 Daltons or greater, most preferably, about 40,000 Daltons. 
Preferably, each B block has a weight average molecular weight of about 
100,000 Daltons or less, even more preferably, about 80,000 Daltons or 
less and most preferably, about 70,000 Daltons or less. Preferably, the 
monovinylidene aromatic polymer block has an effective phase volume in the 
organic phase of about 5 volume percent or greater, more preferably, about 
8 volume percent or greater, even more preferably, about 10 volume percent 
or greater, and even more preferably, about 12 volume percent or greater. 
Preferably, the monovinylidene aromatic polymer block has an effective 
phase volume in the organic phase of about 20 volume percent or less, more 
preferably, about 19 volume percent or less, even more preferably, about 
18.5 volume percent or less and most preferably, about 18 volume percent 
or less. "Organic phase" as used herein, refers to all of the 
organic-based materials in the dispersion, except the surfactant. Such 
materials include the block copolymers and any optional extender. 
A blend of two or more block copolymers may be used in this invention. All 
of the block copolymers used, preferably have A blocks which have weight 
average molecular weights in the range of from, about 4,000 to about 
15,000 Daltons. The composition weighted average monovinylidene aromatic 
monomer content of the blended copolymers is preferably from, about 5 to 
about 30 percent by weight. One or more of the components may have a 
monovinylidene aromatic monomer content outside of the stated range, 
provided the average is within the stated range. In the embodiment, 
wherein one of the block copolymers in such a blend has a monovinylidene 
aromatic monomer content above about 25 weight percent, it is preferred 
that the monovinylidene aromatic monomer content be about 35 weight 
percent or less and, more preferably, about 30 weight percent or less. 
Preferably, the total amount of block copolymer having a monovinylidene 
aromatic monomer content above about 25 percent by weight is about 35 
percent by weight or less and, more preferably, about 30 percent by weight 
or less. The block copolymers can be blended in bulk and thereafter 
emulsified. Optionally, the block copolymers may be emulsified separately 
and the dispersions can be blended. Methods of blending the bulk block 
copolymers or aqueous dispersions of the block copolymers are well known 
in the art. 
In some embodiments of the invention, one or more block copolymers may have 
an effective phase volume of the A block which is greater than preferred. 
In order to reduce the phase volume of the A block, an extender may be 
blended with the block copolymer to reduce the effective phase volume of 
the A block in the organic phase to the required or desired level. 
Extenders useful in the invention are non-volatile organic materials which 
have a greater affinity for the B block than the A block, that is, such 
extenders are soluble in the B block or form a single phase with the B 
block when the extender is mixed with one or more block copolymers. Among 
preferred extenders are hydrocarbon oils, polymers or oligomers derived 
from monomers having olefinic unsaturation compatible with the B block, or 
mixtures thereof. More preferred extenders are the aliphatic hydrocarbon 
and naphthenic oils, with the most preferred class of extender oils being 
the aliphatic hydrocarbon oils. The preferred hydrocarbon oils are 
selected according to the ultimate end use and the cost of such oils. 
Among preferred oils arc Tufflo.TM. 6056 mineral oil (a trademark of 
Atlantic Richfield Company) and Shellflex.TM. 371 mineral oil (a trademark 
of Shell Oil Company). The preferred polymers useful as extenders include 
polyisoprene, polybutadiene, polyisobutylene, polyoctene, polyethylene 
vinyl acetate, polyethylene methacrylate, ethylene-propylene diene 
monomer-based polymers, styrene-butadiene random copolymers, low density 
polyolefins and ethylene-styrene copolymers. Most preferred polymers 
include polyisoprene and polybutadiene. The extenders are present in a 
sufficient amount to achieve the desired effective phase volume of the A 
block. If too much extender is used, the films prepared from the aqueous 
dispersions would not meet the tensile strengths required. The amount of 
extender is preferably about 45 percent by weight or less of the organic 
phase, more preferably, about 40 percent by weight or less and most 
preferably, about 30 percent by weight or less. If present, the extender 
is present in an amount of about 1 percent by weight or greater of the 
organic phase and more preferably, about 5 percent by weight or greater. 
The extender oils can be blended with the block copolymer in bulk and the 
blend can be emulsified. Alternatively, the extender oils and block 
copolymers can be separately emulsified and the dispersions can be blended 
to achieve the desired organic phase composition. In yet another 
embodiment, the extender may be added directly to a dispersion of the 
block copolymers. Methods of performing such blending are well known in 
the art. In the embodiment where the extender is a polymer, the polymer is 
either blended into a solution of block copolymer in organic solvent or 
into a dispersion of the block copolymer. Preferably, the extender is in 
the form of an organic solution or dispersion when blended with the block 
copolymer. 
To achieve the required organic phase composition, a blend of two or more 
copolymers and one or more extenders may be used in combination. 
The percentage of the monovinylidene aromatic monomer block in the block 
copolymer or organic phase, measured as a volume percent, is less than the 
percentage thereof measured by weight. In order to determine the volume 
percent of the monovinylidene aromatic polymer block, the corresponding 
weight percentage of monovinylidene aromatic monomer is divided by a 
correction factor. The correction factor is a value equal to the sum of 
ratios of each monomer's content in weight percent divided by the 
respective density of a homopolymer of such monomer. For a two-component 
block copolymer, this may be expressed as follows in Formula II: 
EQU %(vol.sub.a)=%(wt.sub.a)/D.sub.a /(%(wt.sub.a)/D.sub.a 
+%(wt.sub.b)/D.sub.b)(II) 
where: % (vol.sub.a) is the effective phase volume in percent for the 
monovinylidene aromatic polymer block; 
% (wt.sub.a) and % (wt.sub.b) are the respective weight percent contents of 
monovinylidene aromatic monomer and diene monomer in the block copolymer; 
and 
D.sub.a and D.sub.b are the respective densities of homopolymers, the 
monovinylidene aromatic monomer and diene monomer. 
In those embodiments where an extender is present, the effective phase 
volume of the A block in the organic phase is represented by Formula III: 
EQU %(vol.sub.a)=%(wt.sub.a)/D.sub.a /(%(wt.sub.a)/D.sub.a +%(wt.sub.b)/D.sub.b 
+%(wt.sub.d)/D.sub.d) (III) 
where: % (wt.sub.d) is the weight percent of the extender present, 
D.sub.d is the density of the extender present; and 
the other terms are defined above. 
At lower monovinylidene aromatic monomer effective phase volumes, 
especially for polymers wherein the monovinylidene aromatic monomer block 
molecular weight is relatively low, the tensile properties of the 
resulting films are unacceptably low. At higher monovinylidene aromatic 
monomer effective phase volumes, the dispersion does not readily form 
films, especially at mild temperatures from about 25.degree. C. to about 
90.degree. C. Moreover, films from such polymers require longer periods of 
time under annealing conditions and/or higher annealing temperatures to 
achieve maximum tensile strength properties. Such films are subject to 
polymer degradation resulting in films possessing poor tensile properties, 
especially ultimate tensile strength. 
Preferably, the weight average molecular weight (M.sub.w) of the triblock 
copolymers is about 38,000 Daltons or greater, more preferably, about 
60,000 Daltons or greater, even more preferably, about 76,000 Daltons or 
greater and even more preferably, about 96,000 Daltons or greater, and 
most preferably, about 110,000 Daltons or more. Preferably, the weight 
average molecular weight (M.sub.w) of the triblock copolymers is about 
430,000 Daltons or less, more preferably, about 240,000 Daltons or less 
and most preferably, about 200,000 Daltons or less. In the embodiment 
where the block copolymer is a radial block copolymer, the weight average 
molecular weight is preferably, about 500,000 Daltons or less, more 
preferably, about 400,000 Daltons or less, even more preferably, about 
300,000 Daltons or less, most preferably, about 230,000 Daltons or less. 
Molecular weights are determined by size-exclusion chromatography. 
Commercially available polystyrene standards are used for calibration and 
the molecular weights of copolymers corrected according to Runyon et al., 
J. Applied Polymer Science, Vol. 13, p. 2359 (1969) and Tung, L. H., J. 
Applied Polymer Science, Vol. 24, p. 953 (1979). 
Preferably, the B block of the block copolymers employed herein comprises a 
high 1,4-content polymer of a conjugated diene. By this, is meant, that 
the vinyl functionality of the resulting conjugated diene polymer block is 
preferably below about 10 weight percent for blocks not containing 
butadiene or, in the case of blocks comprising butadiene, preferably below 
about 25 weight percent. 
It is believed (but not agreeing to be bound by such belief) that when the 
monovinylidene aromatic polymer blocks possess the previously stated 
effective phase volume, the monovinylidene aromatic polymer blocks 
coalesce, thereby causing the polymer matrix to possess a particulated or 
spherical morphology instead of a cylindrical or lamellar morphology. Such 
morphology is desirable for the formation of films from dispersions having 
good strength properties and film formation rates. Such morphology, as 
well as the concept of polymer block phase volume, are disclosed in S. L. 
Aggarwal, Block Polymers, Plenum Press, pp. 102-103 (1970). It is further 
believed (but not agreeing to be bound by such belief) that the 
particulated or spherical morphology which is present in the A block is 
the discontinuous phase which facilitates the formation of stable 
dispersions and strong films. 
Block copolymers and techniques for their preparation are well known in the 
art as disclosed in Ser. No. 469,184 filed Jun. 5, 1995, at page 14, line 
14 to page 15, line 22; WO 94/15997 at page 7, line 11 to line 34; and 
U.S. Pat. No. 4,196,154, the teachings of which are incorporated herein by 
reference. 
Surfactants and preferred surfactants useful in the invention are those 
which emulsify the block copolymer(s) and optional extender in water and 
are disclosed in Ser. No. 469,184 filed Jun. 5, 1995, at page 15, line 24 
to page 16, line 8; and WO 94/15997 at page 7, line 35 to page 8, line 10. 
Preferably, the surfactants have an HLB (hydrophobic, lypophobic balance) 
of about 15 or greater and, more preferably, an HLB of about 18 or 
greater. 
The surfactant is present in a sufficient amount to emulsify the block 
copolymer(s) and optional extender(s). If too much surfactant is used to 
prepare the aqueous dispersions, the surfactant will negatively impact the 
tensile properties. Preferably, about 0.5 percent by weight or more of 
surfactant is present and more preferably, 1 percent by weight or more is 
present. Preferably, about 10 percent by weight or less surfactant is 
used, more preferably, about 8 percent by weight is used and even more 
preferably, about 6 percent by weight or less is used. 
To produce an aqueous dispersion (interchangeably referred to herein as a 
dispersion or a latex) the polymer, usually in the form of a solution in 
an organic solvent, is dispersed in water using a suitable surfactant and 
the organic solvent is removed. One suitable procedure is disclosed in 
U.S. Pat. No. 3,238,173 (incorporated herein by reference). Emulsification 
can take place by any of the well-known means for this purpose and the 
specific means utilized does not form an essential aspect of the present 
invention. In one embodiment, the block copolymer and optional extender 
are dissolved in an organic solvent. In such embodiment, a portion of the 
solvent is removed until the solids level is preferably, about 30 percent 
by weight or greater and, more preferably, about 40 percent by weight or 
greater. Preferably, the solids content is as high as possible. The upper 
limit is a practical one, in that the solution must be processable. 
Thereafter, the block copolymer and optional extender are contacted with 
water and surfactant with agitation to emulsify the mixture. Thereafter, 
the remaining solvent is removed by conventional means, such as rotary 
evaporation or vacuum distillation. Preferably, the solids level is about 
20 percent by weight or greater and more preferably, about 28 percent by 
weight or greater. Preferably, the solids level is about 75 percent by 
weight or less, more preferably, about 70 percent by weight or less, even 
more preferably, about 65 percent by weight or less and most preferably, 
about 60 percent by weight or less. Generally, the number average size of 
the resulting latex particles is less than about 5.0 microns and more 
preferably, from about 0.3 to about 2.0 microns. Preferably, the latex 
particles (the dispersed polymer particles in the aqueous medium) are 
spherical in shape. 
The dispersion is frothed by any means which introduces bubbles into the 
emulsion to thereby entrain gas in the emulsion. Such means include 
agitating the emulsion or by bubbling a gas through the emulsion such that 
the emulsion froths. In the embodiment where agitation is used, any means 
of agitation which introduces bubbles into the emulsion is suitable. In 
one preferred embodiment, the agitation is performed by the use of an 
impeller. In this embodiment, the impeller is rotated at a speed so as to 
introduce bubbles and froth the emulsion. In the embodiment, where a gas 
is bubbled through the emulsion, the gases which may be used are any which 
result in the dispersion frothing and which can become entrained in the 
frothed dispersion, and preferably include air, nitrogen, carbon dioxide, 
argon and the like. 
To prepare a film from the frothed dispersion, a suitable form having a 
surface in the shape of the desired resulting product (optionally having a 
surface coating of a suitable substance to promote film removal and/or 
dispersion deposition as previously known in the art) is coated with the 
frothed dispersion and the water is thereafter removed by evaporation. A 
preferred dispersion for use in the manufacture of dipped goods in the 
foregoing manner contains about 20 percent by weight or greater of solids, 
more preferably, from about 25 percent by weight or greater and most 
preferably, about 27 percent by weight or greater. Preferably, the 
dispersion has a solid content of about 70 weight percent or less and more 
preferably, about 60 weight percent or less. A second or further layer may 
be applied in the same manner to achieve thicker films. The film resulting 
from the foregoing procedure may be dried and annealed, if desired, by any 
suitable technique, especially by heating. Preferred temperatures for 
drying and annealing are about 25.degree. C. or greater, more preferably, 
about 30.degree. C. or greater and most preferably, about 50.degree. C. or 
greater. Preferably, the temperatures for drying and annealing the films 
are about 130.degree. C. or less, more preferably, about 120.degree. C. or 
less and most preferably, about 110.degree. C. or less. Preferred times 
for drying and annealing are about 1 minute or greater and more 
preferably, about 4 minutes or greater. Preferred times for drying and 
annealing are about 10 hours or less, preferably, about 60 minutes or less 
and more preferably, 30 minutes or less. At higher temperatures, shorter 
drying and annealing times are required. The drying and annealing steps of 
the process may be conducted simultaneously or separately. For example, 
multiple film layers may be deposited and dried before the resulting 
structure is annealed. 
In one preferred embodiment the films can be prepared using the emulsions 
and processes described in U.S. Pat. No. 5,500,469 (incorporated herein by 
reference) wherein the emulsions have been frothed as described herein. 
Thereafter, the frothed emulsion is placed on a hot surface, such as a 
belt, and the thickness is controlled by a means known to one skilled in 
the art, such as with an adjustable beam. Preferably, the surface is 
heated to a temperature of about 50.degree. C. or greater and more 
preferably, about 60.degree. C. or greater and preferably about 99.degree. 
C. or less and more preferably about 90.degree. C. or less. 
Preferably, the films or elastomeric articles prepared from block 
copolymers which have not been hydrogenated to remove at least 99 percent 
of the residual unsaturation in the conjugated diene block contain an 
antiozonant which prevents or retards degradation due to ozone attack. 
Preferably, the films or elastomeric articles which contain an antiozonant 
do not stain and do not have an unpleasant odor. Preferred antiozonants 
include dialkyl paraphenylenediamines, acetals and styrene-substituted 
phenols. Preferred classes are the acetals and styrene substituted 
phenols. A preferred dialkyl paraphenylenediamine is 
N,N'-di-(2-octyl)p-phenylenediamine, available from R. T. Vanderbilt under 
the trademark Antozite.TM. 1. A preferred acetal is 
bis-(1,2,3,6-tetrahydrobenzaldehyde)-pentaerythrityl acetal available from 
Akrochem Corporation, under the trade name 70TBPA. A preferable 
styrene-substituted phenol is bis-(alphamethylbenzyl)phenol, available 
under the trademark PRODOX.TM. 120 from PMC Specialties Group. The 
antiozonants are used in a sufficient amount to render the films or 
articles of the invention ozone resistant for a period of 1,000 hours. 
Ozone resistance is determined according to the following test. Films 
according to the invention are cut into dumbbell shapes having the gauge 
dimension of 2.5 in. (6.4 cm) (length) by 0.5 in. (1.3 cm) (width). The 
samples are stretched to 100 percent elongation and secured to a hard 
surface at such elongation and exposed to atmospheric ozone. The time from 
the start of the test until the samples break is the ozone resistance. 
"Nonstaining" as used herein, means no transference of a noticeable color 
to white fiberboard during the ozone resistance test. Preferably, the 
antiozonant is present in an amount of about 0.5 percent by weight or 
greater, based on the article or film. Preferably, the antiozonant is 
present in an amount of about 5 percent by weight or less, based on the 
weight of the film or article. The antiozonant can be blended with the 
block copolymer or organic phase in bulk, in solution or in the dispersion 
using techniques well known in the art. Preferably, the antiozonant is 
dissolved in an organic solvent and contacted with a solution of the block 
copolymer or organic phase. Preferably, the same solvent is used for the 
antiozonant as the block copolymer or the organic phase. Preferably, the 
solids level of the antiozonant is the same as the solids level of the 
block copolymer or organic phase as this facilitates formation of a 
homogeneous mixture. 
Preferably, the dispersions and films of the invention contain wax to 
further enhance the ozone resistance. Preferred useful waxes include 
paraffin or microcrystalline waxes having a melting point of from about 
30.degree. C. to about 65.degree. C. Waxes useful in the films and 
dispersions of the invention include 1230 CP Hall No Chek Wax.TM. and 
Mobilcer C Wax.TM. available from Mobil Oil Corporation. Wax is preferably 
present in an amount of about 0.5 percent by weight or greater, based on 
the solids in the dispersion or of the film, more preferably, about 1.0 
percent by weight or greater. Wax is preferably present in an amount of 
about 5.0 percent by weight or less, based on the solids in the dispersion 
or of the film, more preferably, about 4.5 percent by weight or less. 
The film thickness is determined by the ultimate use. The desired film 
thickness for the uses for which the films of the invention may be used 
are well known in the art. Preferably, the films have a thickness of about 
0.03 mm or greater, more preferably, about 0.13 mm or greater and most 
preferably, about 0.20 mm or greater. Preferably, the films are about 3.0 
mm or less and most preferably, about 2.0 mm or less. 
Preferably, the films of this invention are free-standing, which means the 
films do not require a substrate to retain their integrity. 
Films having adhesive properties may be prepared by incorporating a 
suitable tackifier, usually a low molecular weight organic polymer such as 
a polyterpene or similar compound, in the film. Tackifying resins useful 
herein are those known in the art and include hydrogenated rosin esters, 
esters of polyhydric alcohol, phenol-aldehyde resins and hydrocarbon 
resins, which includes polyterpenes. U.S. Pat. No. 5,183,705 provides a 
description of such tackifying resins, relevant portions are incorporated 
herein by reference. Additional formulants such as oils, may also be added 
to modify the adhesive properties of the resulting film. Particularly 
useful oils are hydrocarbon oils, preferably paraffinic and naphthenic 
oils. U.S. Pat. No. 3,935,338 discloses preferred oils useful in adhesive 
formulations, relevant parts incorporated herein by reference. Such oils 
are preferably incorporated in amounts of about 5 to about 20 percent by 
weight of the final adhesive formulation. The tackifiers and other 
formulants may be added to the polymer solution or incorporated into the 
latex. The resulting modified latex may be further concentrated and coated 
onto a substrate, for example, a sheet or a film, such as a masking tape 
backing. The substrate/film combination may thereafter be dried and, 
optionally, annealed to form the final product.

Having described the invention, the following examples are provided as 
further illustration and are not to be construed as limiting. Unless 
stated to the contrary, parts and percentages are expressed on a weight 
basis. Effective phase volumes were calculated using the previously 
disclosed Formulae (II and III). For such calculations, the densities of 
the respective polymers used were polystyrene: 1.047, polyisoprene: 0.91 
and polybutadiene: 0.90. 
EXAMPLE 1 
Films of Styrene-Isoprene-Styrene Block Copolymer 
An aqueous dispersion was formed from a cyclohexane solution of a 
styrene-isoprene-styrene triblock copolymer having a total M.sub.w of 
140,000 Daltons, and a styrene content of 18 weight percent and 17.5 
volume percent (effective phase volume). The surfactant used was Rhodopex 
Co-436.TM., available from Rhone Poulenc, sulfated 
nonylphenoxypoly-(ethyleneoxy) ethanol at a 3 percent by weight level. 
Molecular weights were determined by gel permeation chromatography using 
polystyrene standards and corrected for diene content. The polystyrene 
endblocks had weight average molecular weights of 12,600 Daltons. The 
total polyisoprene block M.sub.w was 114,800 Daltons. The solvent was 
removed and the dispersion concentrated to 52 percent solids by weight. To 
a container filled with this dispersion, a nitrogen purge (15 mL 
volume/minute) was initiated and allowed to continue for 16 hours. During 
this time, the dispersion entrained a significant number of air bubbles. 
When a heated mold was dipped into the dispersion, a uniform breathable 
film was produced. The foamed material was annealed at 90.degree. C. for 
20 minutes in a forced-air oven. When the article was filled with water, 
no holes were detected. However, once a slight pressure was applied, small 
water droplets were displaced to the surface. Air could be blown through 
the film. 
EXAMPLE 2 
A styrene-isoprene-styrene block copolymer having a M.sub.w of 140,000 
Daltons and a styrene weight percentage of 18 percent, 17.5 styrene volume 
percent, and a styrene block molecular weight of 12,600 Daltons was 
dispersed in water as described in Example 1 to a percent solids of 42 
percent by weight. The surfactant used in the dispersion was Dresinate 
731D.TM. acid form of a modified rosin (available from Hercules), having 
an average molecular weight of 302 in an amount of 3 parts per hundred 
parts of block copolymer with an equimolar amount of potassium hydroxide 
to the dispersion. The pH of the dispersion was adjusted to 10.5. 10 grams 
of Rhodopex Co-436.TM. was added to 200 grams of this dispersion and 
blended in a high shear mixer for 10 minutes. The mixer is an overhead 
utility blender operated at 10,000 rpm. The mixing caused the latex to 
expand to 4 times its original volume. The additional volume was due to 
entrained air. An approximately 15 gram amount was poured on a level glass 
plate which was at room temperature. The foam was drawn to 40 mils thick 
using a draw bar. The film was left standing for 2 minutes and then the 
plate and film were placed in a forced-air oven maintained at 90.degree. 
C. for 20 minutes. The plate was removed and allowed to cool. The foam 
produced a breathable film once it was removed from the plate. A second 
sample was prepared by the same procedure except that the foamed 
dispersion was drawn across a glass plate preheated to approximately 
60.degree. C. After treating the second sample as described above, the 
foam structures were compared. In the case where the plate was heated, the 
cell structure appeared to be more open. 
EXAMPLE 3 
A hydrogenated styrene-butadiene-styrene block copolymer having two styrene 
chains with an M.sub.w of 11,700 Daltons and a central hydrogenated 
butadiene chain of 54,000 Daltons available from Shell Chemical Co. under 
the trademark and designation Kraton.TM. G 1652, nominally containing 55 
parts of oil per hundred parts of block copolymer was dissolved in 
cyclohexane to form a 36 percent by weight solids solution. The amount of 
styrene in the organic phase is 19 percent by weight and 18 percent by 
volume. Dresinate.TM. 73D surfactant with an equimolar amount 3 parts per 
hundred of block copolymer of potassium hydroxide was added to the 
dispersion. The pH was adjusted to about 10.5. Approximately 200 grams of 
the dispersion was placed into a container and mixed under high shear 
conditions for 10 minutes. The resulting foam was poured onto a glass 
plate and drawn down to 25 mils (0.64 mm) thick. The foam was placed into 
an oven maintained at 100.degree. C. for 20 minutes. After annealing, the 
foam was removed from the oven, allowed to cool and removed from the 
glass. The foam was breathable and strong. 
EXAMPLE 4 
Dispersions of Example 2 were foamed and poured onto a glass plate. Several 
foams were leveled with bars having differing gaps. After annealing, the 
foam thicknesses were measured, and the original bar thickness and final 
film thickness are listed below for the samples. The data demonstrates 
that films of differing thickness can be prepared. 
______________________________________ 
Bar Gap Bar Gap Thickness 
Thickness 
Sample (mil) (mm) (mil) (mm) 
______________________________________ 
1 50 1.25 12 .3 
2 30 .75 7 .18 
3 20 .50 5 .13 
4 10 .25 3 .08 
______________________________________ 
EXAMPLE 5 
Adhesive Foam 
A dispersion of styrene-butadiene radial block copolymer having 21 weight 
percent styrene, a total weight average molecular weight of 305,000, 4 
arms, a styrene block molecular weight of about 16,000 Daltons and a 
styrene volume percent of 19.5, 3 parts per hundred parts of Dresinate.TM. 
731D surfactant, equimolar amounts of potassium hydroxide, oil and 
tackifier was prepared as in Example 1 and pH adjusted to 10.5. A foam was 
prepared as described in Example 2. The foam was tacky yet still 
breathable. The foam tacked to a metal surface much like a conventional 
pressure sensitive adhesive.