CA1300779C - Block copolymer-polyolefin elastomeric films - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An elastomeric film which includes from at least about 10 percent, by weight, of an A-B-A' block copolymer where "A" and "A' n are each a thermoplastic endblock which has a styrenic moiety and where "B" is an elastomeric poly (ethylene-butylene) midblock and from greater than 0 percent,, by weight, and up to about 90 percent, by weight, of a polyolefin which, when blended with the A-B-A' block copolymer and subjected to an effective combination of elevated temperature and elevated pressure conditions, can be extruded, in blended form, with the A-B-A' block copolymer is disclosed. A method for forming the film is also disclosed.

Description

3 3~

The present invention is generally directed to certain elastomeric films and methods for their formation.

For quite some time those in the art have been attempting to form elastomeric resins into elastomeric films~ In fact, the prior art reveals that experimentation with *RRATON G 1650 and *KRATON G 1652 brand materials has occurred. For example, U.S. patent 4,323,534 to des Marais discloses that it was concluded by those in the art that the *KRATO~ G rubber resins are too viscous to be extruded alone without substantial melt fracture of the product.
However, des Marais does disclose a process which utilizes blends of *KRATON G 1650 or *KRATON G 1652 resins with stearic acid in the formation of fibrous nonwoven webs and films. In order to overcome the stated viscosity problem the *KRATON G 1650 block copolymer or *KRATON G 1652 block copolym~r resin was blended with about 20 percent to 50 percent, by weight r of a fatty chemical such as stearic acid prior to e~tru~ion and meltblowiny or ilm ormation. An extruslon temperature range o 400 to 460 de~rees Fahrenheit is disclosed at column 8, line 64 et.
se~. Unfortunately, the physical properties o the product obtained by this process, for example, a film, were apparently unsatisfactory because, after formation of the ilm, substantially all the fatty chemical is leached out of the ilm by soaking the film in alcohols having a good ability to solubilize the fatty chemical utilized. The leaching of the stearic acid out rom the film is discussed at column 8, line 67 et. seq. In one embodiment, discussed at column 3, lines 8 and 9, the thermoplastic rubber resin is an A-B-A block copolymer wherein B is poly (ethylene-butylene) and the A components are selected from *Trade Mark ?C~`77~31 the group including polystyrene and p~dy (alpha-methylstyrene~.
U.S. Patent 4,305,990 to Kelly discloses that A-B-A
block copolymers having a polybutadiene or polyisoprene midblock and polystyrene endblocks may be extruded as films when blended with an amount of amorphous polypropylene sufficient to enhance the processability of the blend. It is stated in the abstract that the films retain their elastomeric properties and are significantly more processable owing to the presence of the amorphous polypropylene.
Another patent apparently dealing with subject matter stemming from or at least related to the subject matter disclosed in des Marais is U.S. patent 4,355,4~5 to Jones which discloses an undergarment that may be made of a fiber formed by meltblowing a blend of a *KRATON G rubber with stearic acid. The examples are apparently limited to *KRATON G-1652 block copolymers. An extrudable composition, which is stated to be particularly useful at column 4, line 24 et. seq., is a blend o *KRATON G 1652 rubber and 20 percent by weight skearic acid as well as minor amounts of other materials. An extrusion temperature of 390 degrees Fahrenheit for the blend of *KR~TON G 1652 rubber and ~ stearic acid, which is disclosed at column 5, lines 14 and J 19 t iS within the temperature range set forth in the above-mentioned Shell Chemical Company technical bulletins. It is further stated that fibers for making the material can be meltblown as taught in U.S. patent 3,825,380, to Harding which is said to disclose a die configuration suited for meltblowing the fibers. It should also be noted that the procedures of Jones~ as was the case with the procedure of des Marais, indicate the desirability of leaching out the fatty chemical after formation of a fibrous nonwoven web or film from the blend of fatty chemical and *KRATON G. See, for example, column 5, lines 60 et seq.
*Trade Mark ~ .

," --13~

A significant amount of literature has been published with regard to A-B-A' block copolymer sold under the trade designation KRATON by the Shell Chemical Company. For example, Technical Bulletins SC: 38-82 and SC: 39-85 of The Shell Chemical Company of Houston t Texas, in describing polystyrene/poly (ethylene-butylene)/polystyrene elastomeric block copolymer resins sold by it under the trademark KRATON
state that, with respect to the KRATON G 1650 and KRATON G
1652, both of which are block copolymer resins, compounding temperatures of the resin should not be allowed to exceed 525 degrees Fahrenheit, that is 274 degrees Centigrade and that a fire watch should be maintained if the temperature of the resins reaches 475 degrees Fahrenheit, that is 246 degrees Centigrade. With respect to the *KRATON GX 1657 block copolymer resin, Shell Technical Bulletin SC: 607-84 gives a warning not to allow the temperature of the block copolymer resin to exceed 45n degrees Fahrenheit, that is 232 degrees Centigrade, and to maintain a fire watch should that temperature be reached.
Shell Material Safety Data Sheet designated as M5DS number 2,136 states, with respect to KRATON Ç-1657 thermoplastic rubber, that the processing temperature of ~he material should not be allowed to exceed 550 degrees Fahrenheit and thak a ~ire watch should be maintained if that temperature is reached. A Shell Material Safety Data Sheet designated as M5DS 2,031 1 states, with respect to KRATON G-1652 thermoplastic rubber, that the processing temperature of the material should not exceed 550 degrees Fahrenheit and that a fire watch should be maintained if that temperature is reached. Shell Chemical Company Technical Bulletins SC: 68-85 "KRATON Thermoplastic Rubber" and SC: 72-85 "Solution Behavior Of KRATON Thermoplastic Rubbers" give detailed information concerning various thermoplas-tic block copolymer resins which may be obtained from Shell under the trade designation KRATON. The KRATON thermoplastic resins are stated by Shell to be A-B-A block copolymers in which * Trade Mark ~' Y~

' ~3~
.. ~ -- s the "A" endblocks are polystyrene and the "B" midblock is, in KRATON G resins, poly (ethylene-butylene) or, in KRATON D
resins, either polyisoprene or polybutadiene.
Shell Chemical Company Technical Bulletin SC: 198-83, at page 19, gives examples of commercially available resins and plasticizers usable with KRATON rubber resins. The Bulletin distinguishes between rubber phase, B midblock, associating materials and polystyrene phase, A endblock, associating materials. Among the rubber phase associating materials is a qroup of resins which are identified as "Polymerized Mixed Olefin" and a plasticizer identified as "Wingtrack 10" having a chemical base of "mixed olefin".
The present invention overcomes the above-discussed difficulties which have been encountered by those in the art when attempting to form elastomeric A-B-A' block copolymer materials into elastomeric films. For example, leaching of materials out of the elastomeric films formed from the elastomeric block copolymers is avoided. The elastomeric film is ormed from a blend of (1) from at least about 10 percent, by weight, of an A-B-A' block copolymer, where "A" and 'IA"' are each a thermoplastic polymer endblock which includes a ~tyrenic moiety and where "B" is an elastomeric poly ~ethylene-butylene) midblock, with t2) greater than 0 percent, by weight, to about 90 percent, by weight, o a polyolefin which, when blended with the A-B-A' block copolymer and subjected to appropriate, i.e. effective, elevated pressure and elevated temperature conditions, is extrudable, in blended form, with the A-B-A' block copolymer.
Another aspect of the invention resides in a process an elastomeric film from an extrudable composition comprising from at least about 10 percent, by weight, of a A-B-A' block copolymer where "A" and "A"' are each a thermoplastic end block which includes a styrenic moiety and where "B"' is an elastomeric poly tethylene-butylene) midblock, and from greater than 0 percent by weight to about 90 percent by weight of a polyeofin which, when blended with A-B-A' block copolymer and subjected to an effective combination of elevated temperature and elevated pressure conditions, is adapted to be extruded, in blended form, with A-B-A' block copolymer.
The method includes the step of subjecting the extrudable composition to a combination of elevated temperature and elevated lD pressure conditions, sufficient to effect extrusion of the extrudable composition from a film die as a molten film. The method further includes the steps of drawing the molten film to reduce the thickness of the molten film, and cooling the molten film by quenching.
The A-B-A' block copolymer serves to impart elastomeric properties to the films formed from the extruded blend and the presence of the polyolefin in the extruded blend serves to reduce the viscosity of the extruded blend as compared to the viscosity of the neat, i~e. pure, A-B-A' block copolymer and thus enhances the extrudability of the blend.

More speciEically, the "A" and "A"' thermoplastic styrenic moiety containing endblocks oE the block copolymer are selected from the group including polystyrene and polystyrene homologs such as, for example, poly ~alpha-methylstyrene). In some embodiments, the 'IA'' and "A"' thermoplastic styrenic moiety containing endblocks are identical. Preferably, the polyolefin is selected from the group including at least one polymer selected from the group including polyethylene, polypropylene, polybutene, ethylene copolymers, propylene copolymers, butene copolymers or blends of two or more of these materials.
Preferably, the sum of the molecular weight of the polystyrene endblock "A" with the molecular weight of the polystyrene endblock "A"' is from at least about 14 percent to about 29 percent of the molecular weight of the A B-A' block copolymer.

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- 6a -The blend usually includes from at least about 20 percent, by weight, to about 95 percent, by weight, of the block copolymer and from at least about 5 percent, by weight, to about 30 percent, by weiyht, of the polyolefin. For example, the blend may include from about 30 percent, by weight, to about 90 percent, by weight, o~ the block copolymer and from about 10 percen~, by weight, to about 70 percent, by weight, of the polyolefin. Preferably, the blend includes from about 50 percent, by weight, to about 90 percent, by weight, of the block copolymer and from about 10 percent, by weight, to about 50 percent, by weight, of the polyolefin. For example, the blend may include from about 50 percent, by wei~ht, to about 70 percent, by weight, of the blo~k copolymer and from about 30 percent, by weight, to about 50 percent, by weight, of the polyolefin. One exemplary blend includes about 70 percent, by weight, of the block copolym-er, about 20 percent, by weight, of the polyolefin and about - 7 ~

10 percent, by weight, of another material. Another exemplary blend includeS about 60 percent, by weiaht, of the block copolymer, about 30 percent, by weight, o the polyolefin and about 10 percent, by weight, of material.
If a polyethylene i5 utilized as the polyolefin in the blend, the polyethylene preferably has a density of about 0.903 grams per cubic centimet2r. It is also preferred for the polyethylene to have a Brookfield viscosity cP at 150 degrees Centigrade of 8500 and at 190 degrees Centigrade of 10 3300 when measured in accordance with ASTM D 3236, a number average molecular weight (Mn) of about 4,600, a weight average molecular weight (Mw) of about 22,400, a Z average molecular weight (~z) of about 83,300 and a polydispersity (Mw/Mn) o about 4.87.
I a polypropylene is utilized for the polyolefin in the blend, the polypropylene may have a density of about 0.900 grams per cubic centimeter when measured in accordance with AS~M D 792. The polyolefin may also have a meltflow value, obtained in accordance with AST~ D 1238, 20 condition L, of about 35 grams per 10 minutes, a number averaga molecular weight (Mn) o about 40,100, a weight average molecular weigh~ (Mw~ of about 172,000, a Z average molecular weight ~MZ) of about 674,000 and a polydispersity (Mw/Mn) of about 4.29.
If a polybutene i5 utilized as the polyolefin in the blend, the polybutene may be an isobu~ylene-butene copolymer.
; Elastomeric films having a thickness of no greater than about 25 mils may be formed from the extrudable 30 compositions discussed above. Preferably, the elastomeric films have a thickness of not more than about 10 mils, for example, the elastomeric films may have a thickness of no greater than abol~t 3 mils.
Preferably, the elastomeric films are formed by 35 extrusion through a film forming die at a temperature of at least about 125 degrees Centigrade if the polyolefin is a - 8 - ~3~13~

polyethylene or at least about 175 degrees Centigrade if the polyolefin is polypropylene, for example, from about 290 degrees Centigrade to about 345 degrees Centigrade, more specifically, rom about 300 degrees Centigrade to 5 about 325 degrees Centigrade.
The elastomeric film is formed by extruding the extrudable composition from a film-forming die as a molten material, drawing the molten material to reduce the thickness of the molten material to that of a film and 10 cooling the molten film by, for example, ~uenching the drawn molten film in a water bath.
Still other aspects of the present invention will become apparent to those skilled in the art upon review of the following detailed disclosure.
DEFINITIONS

The terms "elastic" and "elastomeric" are used interchangeably herein to mean any material which, upon 20 application of a biasing orce, is stretchable to a stretched, biased length which i9 at least about 125 percent, that is about one and one quarter, o its relaxed, unbiased length, and which, will recover at least 40 percent of its elongation upon release of the 2S stretching, elongating force. ~ hypothetical example which would satisfy this definition of an elastomeric material would be a one (1) inch sample of a material which is elongatable to at least 1.25 inches and which, upon being elongated to 1.25 inches and released, will recover to a 30 length of not more than 1.15 inches. ~any elastic materials may be stretched by much more than 25 percent of their relaxed length and many of these will recover to substantially their original relaxed length upon release of the stretching, elongating force and this latter class of 35 materials is generally preferred for purposes of the present invention.

_ q- ~L3~ i9 As used herein the term "recover" refers to a contraction of a stretched material upon termination of a biasing force following stretchLnq of the mater~al by application of the biasing force. For example, if a 5 material having a relaxed, unbiased length of one (1) inch was elongated 50 percent by stretching to a lenqth of one and one half ~1.5) inches the material would have beer elongated 50 percent and would have a stretched length that is 150 percent of its relaxed length. If this exemplary 10 stretched material contracted, that is recovered to a length of one and one tenth (1.1) inches after release of the biasing and stretching force, the material would have recovered 80 percent (0.4 inch) of its elongation.
As used herein the term ~styrenic moiety" refers to a 15 monomeric unit represented by the formula:

{~ CH2--C~ ~
/c~
CH CH
Il I
CH CH
CH

Ag used herein the term "poly (ethylene-butylene)"
refers to a polymer seqment or block represented by the formula:
~oly~e~hylen~nutyl~nel f~ Cl~ Cll:~H--C~

where x, y and n are positive integers.

~ 3~ ~ ~ 7~

As used herein the term "polystyrene" rerers to a polymer segment or block represented by the formula:
Ch7 -- Ch C ?o~yStyrer~
C H C 1~
C~ CH
CH
where n is a positive integer~
Unless specifically set forth and defined or otherwise 10 limited, the terms "polymer" or ~polymer resin" as used herein generally include, but are not limited to, homopolymers, copolymers, such as, for example, bloc~, graft, random and alternating copolymers, terpolymers, etc.
and blends and modifications thereof. Furthermore, unless 15 otherwise specifically limited, the terms "polymer~ or "polymer resin~ shall include all pos~ible geometrical configurations of the material. These configuration~
include, but are, not limited to, isotactic, syndiotactic and random symmetries.
As used herein the term "consisting essentially of"
does nOt exclude the presence of additional materials which do not significantly affect the elastic properties and characteristics of a given composition. Exemplary material~ o this sort would include, with~ut limitation, 25 pigments, antioxidan~s, stabilizers, surfactants, waxes, 10w promoters, solid solvents, particulates and materials added to enhance processability of the composition.

~IEF DESCRIPTION OF THE DRAWING
Figure 1 is a schematic representation illustrating apparatus for forming elastomeric films in accordance with the present inventionO
Figure 2 is a plan view of the die arrangement 35 illustrated in Figure 1 as viewed from the line 2-2 in Figure 1.

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- , . , !, ' '~ ~

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D~SCRIPTION OF THE P ~ERRED E~IBODIMENTS

It has now been found that a blend of from g-eater than O percent, by weight, to about 90 percent, by wei~ht, 5 of one or more polyolefins with from at least about 10 percent, by weight, of certain A-B-A' block copolymer elastomeric resins can be extruded and formed into films under appropriate, i.e. effective, elevated temperature and elevated pressure conditions to provide satisfactory 10 elastomeric films. Preferably the material is extr~ded through the film die at a temperature of at least about 125 degrees Centigrade if polyethylene is utilized as the polyolefin in the blend or at least about 175 degrees Centigrade if a polypropylene is utilized as the polyolefin 15 in the blend, for example at a temperature of from at least about 290 degrees Centigrade to about 345 degrees Centigrade, more specifically from a temperature of from at least about 300 degrees Centigrade to about 335 degrees Centigrade.
The A-B-A' elastomeric block copolymers which may be utilized generally include A-B-A' block copolymers whère A
and A' are each a thermoplastic polymer endblock which contains a styrenic moiety such as, for example, a poly ~vinyl arene) where, in some embodiments, A may be the same 2S thermoplastic polymer endblock as A', and where B is an elastomeric poly (ethylene-butylene) polymer midblock.
Preferably, the A and A' endblocks are selected from the group of materials including polystyrene or polystyrene homologs such as, for example, poly (alpha-methylstyrene).
30 Materials of this general type, that is KRATON G 1650 and KRATON G 1652, are disclosed in U.S. patents 4,323,534 to des Marais and 4,355,425 to Jones and in the aforementioned Shell brochures which also disclose KRATON GX 1657 materials. Commercially available elastomeric A-B-A' block 35 copolymers having a saturated or essentially saturated poly - 12 - ~3~

(ethylene-butylene) midbloCk o- ,ecmen~ "3" eDresented by the formula:
~oly~etrylen~ou~ ene) ~ n where x, y and n are positive integers and polystyrene endbloc~s or segmentq "A" and "A'~ each represented by the 10 formula:
CH~--CH

CH CH
Il I
CH CH
//
CH
,1 5 polysrlr~na where n is a positive integer which may be of the same or a different integer for the A and A' endblocks, are sometimes referred to as S-EB-S block copolymers and are available 20 under the trade designation KRATON G, ~or example, KRATON G
1650, KRATON G 16i2 and XRATON GX 1657, from the Shell Chemical Company.
A summary of the typical properties, as published by the Shell Chemical Company, of the above-identified KRATON
2S G resins at 74 degxees Fahrenheit is presented below in Table I~

.

., . : , .

- 13 - ~3 TA~3LE I

KRATON G

Tensile Strength, 2 2 10 psi 5ro002 4,500 3,400 300~ Modulus, psil 800 700 350 Elongation, ~1500 500 750 Set at B.reak, ~

Hardness, Shore A 7S 75 65 Specific Gravity 0.91 0.91 0.90 Bro~kfield Viscosity, ~Toluene Solution) cps at 77 ~F1,5003 5503 1,200 25 Melt Viscosity, Melt Index, Condition G, sms/10 min. - - -30 Plasticizer Oil Content~ ~w 0 0 0 Sytrene/Rubber Ratio 28/72 29/71 14/86 Physical FormCrumb Crumb Pellet - 14 - ~3~ 9 1 ASTM method D4l2-tensile test jaw separation speed 10 in.Imin.
2 Typical properties determined on film cast from a toluene solution.
5 3 Neat polymer concentration, 20~w.

4 The ratio of the sum of the molecular weights of the endblocks (A~A') to the molecular weight of the B
midblock. For example, with respect to KRATON G-1650, the sum of the molecular weights of the endblocks (A+A') is 28 percent of the molecular weight of ~he A-B-A' block copolymer.

Generally, the block copolymer resin must be one which is free of polymer segments which chain scission or which 15 crosslink at the temperatures utilized by the process of the present invention because such materials will either tend to plug up the die through which the molten extrudable composition must be extruded or will overly degrade and form unsatisfactory product. Surprisingly, it has been 20 found that, even at hlgh polyolefin contents, such, as, for example, polyolein contents o 30 percent, by weight, films having elastomeric properties can be formed without the necessity of a post formation treatment such as, for example, leaching to xemove the additives rom the film.
The polyolein which is utilized in blending the extrudable composition must be one which, when blended with the A-B-A' block copolymer and subjected to-an appropriate combination of elevated pressure and elevated temperature conditions, as defined herein, is extrudable, in blended 30 form, with the A-B-A' block copolymer. In particular, preferred polyolefin materials include polyethylene, polypropylene and polybutene, including ethylene copolymers, propylene copolymers and butene copolymers.
Blends of two or more of the polyolefins may be utllized.
35 A particularly preferred polyethylene may be obtained from U.S.I. Chemical Company under ~he trade designation - 15 - ~3~79 Petrothene Na601. (Also referred to as PE Na601.) A
polypropylene may be obtained from The Himont Corporation 5 under the trade designation PC-~73. A polybutene may be obtained from Amoco under the trade designation Indopol L-14.
Information obtained from U.S.I. Chemical Company states that the *Na601 is a low molecular weight, low 10 density polyethylene for application in the areas of hot ~ melt adhesives and coatings. U.S.I. has also stated that : the Na601 has the following nominal values: (1) a Brookfield Viscosity, cP at 150 degrees Centigrade of 8500 and at 190 degrees Centigrade of 3300 when measured in 15 accordance with ASTM D 3236; (2) a density of 0.903 grams pe~ cubic centimeter when measured in accordance wi~h ASTM
D 1505; (3) an equivalent Melt index of 2000 grams per ten minutes when measured in accordance with ASTM D 1238; (4) a ring and ball softening point of 102 degrees Centigrade 20 when measured in accordance with ASTM E 28; (5) a tensile of 850 pounds per s~uare inch when measured in accordance with ASTM D 6387 (6) an elongation o 90 percent when measured in accordance with ASTM D 638; (7) a modulus of Rigidity, TF ~45,000) Of -34 degrees Centigrade and (8) a 25 penetration Hardness, (tenths of mm) at 77 degrees Fahrenheit o 3.6.
The Na601 is believed to have a number average molecular weight (Mn) of about 4,600; a weight average molecular weight ~Mw) of about 22,400 and a Z average 30 molecular weight ~Mz) of about 83,300. The polydispersity ~Mw/Mn) of the Na601 is about 4.87.

Mn is calculated by the formula:

35 Mn = Sum[(n)(M_)]
Sum(n) ~rade Mark ~r~ .st "`'` :

- 16 - ~3 Mw is calculated by the formula:

Mw = Sum[(n)(MW)2]
Sumt(n)(MW)]
Mz is calculated by the formula:

Mz = Sum[(n)(MW)3 5um[(n)(MW) ]
where:
MW = The various molecular weights of the individual molecules in a sample, and n = The number of molecules in the given sample which have a given molecular weight o MW.

Typical characteristics of the Himont PC-973 polypropylene as stated by Himont are a density of about 0.900 grams per cubic centimeter measured in accordance 20 with ASTM D 792. A meltflow rate obtained in accordance with ASTM D 1238, Condition L, of about 35 grams per ten (10) minutes. Other characteristics of the PC-973 are a tensile of about 4,300 pounds per square inch (psi) measured in accordance with ASTM D638; a flex modulus of :25 about 182,000 p9i measured in accordance with ASTM D 790,B
and a rockwell hardness, R scale, of about 93 measured in accordance with ASTM D 785A. The PC-973 is believed to have a number average molecular weight (Mn) of about 40,100; a weight average molecular weight (Mw) of about 30 172,000 and a Z average weight (Mz) of about 674,000~ The polydispersity of the PC-973 (Mw/Mn~ is about 4.29.
Amoco literature states that the Amoco - polybutenes are a series of isobutylene-butene copolymers composed predominantly of high molecular weight mono-olefin 35 (95 percent-100 percent) with the balance being ~3'V~7~

isoparaffins. Typical propertles of the L-14 polybutene as stated by Amoco literature are reported in Table II below.

TABLE II

Test Method L-14 ~ . . _ 10 Viscosity D445 cSt at 38C (100F) 27~33 cSt at 99C (210F~ --Flash Point COCC(F)I Min D92 138 (280) API Gravity at 16C (60F) D287 36-39 15 Color APHA
Haze Free, Max. 70 Haze, ~ax. 15 Appearance . VisualNo Foreign Material 20 Viscosity, SUS at 38C ~100F) 139 SUS at 99C ~210F) 42 Average Molecular Weight Vapo~ Phase320 Osmometer Viscosity Index ASTM D567 69 25 ~ire Point COC, C ~F) ASTM D92154 ~310) Pour Point, C ~F) ASTM D97-51 (-60) Specific Gravity 15.6/15.6 C
~60/60F) 0.8373 Density, Lb/Gal 6.97 30 Ref. IndeX~ N20D ~STM-D12181.4680 Acidity, mg KOHlg ASTM D974 0.03 Total sulfur, ppm X-Ray 6 The blend usually includes from at least about 35 20 percent, by weight, to about 95 percent, by weight, of the block copolymer and from at least about 5 percent, by - 18 - ~3~J~

weight, to about 80 percent, by weight, of the polyolefin.
For example, the blend may include from at least about 30 percent, by weight, to about 90 percent, by weight, of the block copolymer and from at least about 10 percent, by 5 weight, to about 70 percent, by weight, of the polyolefin.
Preferably, the blend includes from at least about 50 percent, by weiqht, to about 90 percent, by weight, of the bloc~ copolymer and from at least about 10 percent, by weight, to about 50 percent, by weight, of the polyolefin.
10 For example, the blend may include from about 50 percent, by weight, to about 70 percent, by weight, of the block copolymer and from about 30 percent, by weight, to about 50 percent, by weight, of the polyolefin. One blend includes about 70 percent, by weight, of the block 15 copolymer, about 20 percent, by weight, of the polyolefin and about 10 percent, by weight, of another material.
Another blend includes about 60 percent, by weight, of the block copolymer, about 30 percent, by weightr of the polyolefin and about 10 percent, by weight, of another 20 material.
The preferred ~levated temperatures of extrusion and the presence of the specified polyolefin in the blend reduces the viscosity o~ the blend, as compared to the viscosity o~ the pure, i.e. neat, A-B-A' block copolymer, 25 and thus forms the blend into an extrudable composition which can be utilized to form the elastomeric ilms of the present invention. However, both the block copolymer-resins and the polyolefins must be able to sustain the extrusion temperatures utilized by the method of the 30 present invention without undergoing excessive chain scission or excessive thermal or oxidative degradation. In this regard it is believed that the degree of oxidative degradation sustained by the extrudable composition may be reduced by blanketing the raw pellets of the resins 35 utilized with an inert gas prior to their processing by an extruder. The fact that the amount of oxidative - 1 9 - 1 30Q7';J9 degradation which the block copolymer undergoes dur'ng extrusion may be reduced by blanketing the raw pellets with an inert gas is generally implied by thermogravimetric analyses of KRATON GX 1657 block copolymer resin which were 5 carried out in air and nitrogen. In these analyses samples of the KRATON GX 1657 block copolymer resin, when heated in air, showed a weight loss beginning at about 307 degrees Centigrade whereas a comparison sample heated in nitrogen showed only a weight loss starting at about 375 degrees 10 Centigrade. It is believed that these results indicate that the effects of oxidative degradation on the sample heated in air could be avoided or diminished by blanketing the raw pellets with an inert or, at least, a non-oxidizing gas.
lS Referring now to the drawings where like reference numerals represent like structure or like process steps and, in particular, to Figùre 1 which schematically illustrates apparatus for forming an elastomeric film in accordance with the present invention, it can be seen that 20 a blend (not shown) of ~a) from at least about 10 percent, by weight, of an A-9-A' block copolymer where A and A' are both thermoplastic polymer endblock~ containing a styrenic moiety such as, for example, a poly (vinyl arene) and where 3 is an elastomeric poly (ethylene-butylene) midblock, with 25 (b) from greater than 0 percent, by weight, to about ~0 percent ! by weight, of a polyolefin which, when blended with the A-B-A' block copolymar and- subjected to an effective combination of elevated temperature and elevated pressure conditions, is extrudable in blended form with the 30 A-B-~' block copolymer, is supplied in, for example, pellet form to a hopper 10 of an extruder 12. The components of the blend may be supplied in pellet or other form. The components (i.e., pellets) may be blanketed with an inert or, at least, non-oxidative gas while in the hopper 10.
- 35 This is believed to reduce the effects of oxidative degradation on the blend by both reducing the contact of - 20 - ~3~

the blend with normal atmosphere while in the hopper 10 and also increasing the likelihood that any gas that is drawn into and through the extruder 12 will be the iner- gas as opposed to oxygen-containing normal atmosphere. The blend 5 usually includes from at least about 20 percent, by weight, to about 95 percent, by weight, of the block copolymer and from about 5 percent, by weight, to about 80 percent, by weight, of the polyolefin. For example, the blend may include from about 30 percent~ by weight, to about 10 90 percent, by weight, of the bloc~ copolymer and from about 10 percent, by weight, to about 70 percent, by weight, of the polyolefin. Preferably, the blend lncludes from about 50 percent, by weight, to about 90 percent, by weight, of the block copolymer and from about 10 percent, 15 by weight, to about 50 percent, by weight, of the polyolefin. For example, the blend may include from about 50 percent, by weight, to about 70 percent, by weight, of the bloc~ copolymer and from about 30 percent, by weight, to about 50 percent, by weight, of the polyolefin. One of 20 the hereinafter discussed examples includes about 60 percent, by weight, of the block copolymer, about 30 percent, by weight, of the polyolefin and about 10 percent, by weight, o another material. The other hereinafker discussed example includes about 70 percent, by 25 weight, of the block copolymer, about 20 percent, by weight, o the polyolein and about 10 percent, by weight, of another material.
The temperature of the blend is elevated within the extruder 12 by a conventional heating arrangement (not 30 shown) to melt the blend and pressure is applied to the blend by the pressure-applying action of a turning screw (not shown~, located within the extruder, to form the blend into an extrudable composition. Preferably the blend is heated to a temperature of at least about 125 degrees 35 Centigrade if polyethylene is utilized as the polyolefin in the blend or at least about 175 degrees Centigrade if - 21 - ~3~

polypropylene i5 utilized as the polvolefin in the blend, for example, to a temperature of from at least about 290 degrees Centigrade to about 345 degrees Centlarade, more specifically, to a temperature of from at least about 300 5 degrees Centigrade to about 335 degrees Centigrade. The combination of eleva~ed temperature and elevated pressure conditions which effect extrusion of the composition will vary over wide ranges. For example, at higher elevated temperatures, lower elevated pressures will result in 10 satis~actory extrusion rates and, at higher elevated pressures of extrusion, lower elevated temperatures will effect satisfactory ex~rusion rates.
The extrudable composition is then forwarded by the pressure applying action of the turning screw to a film die 15 14. The rate of rotation of the turning screw is adjusted so that the blend is under at least about 100 pounds per square inch, gage (psi,g) of pressure in the film die 14.
Preferably, the blend is under from about 100 psi,g to about 500 psi,g of pressure in the film die 14. For 20 example the blend may be under rom about 200 psi,g to about 350 psi,g of pressure in the ilm die 14, more specifically from about 27S psi,g to about 325 psi,g of pressure in the film die 14. The elevated temperature of the extrudable composition is maintained in the film die 14 25 by a conventional heating arrangement tnot shown). The die 14 has a die slot opening 16 which generally extends a distance 18 which is approxima~ely equal to the width of the film 20 which is to be formed by the process. The slot 16 of the die 14 has a gap 22, usually adjustable, which 30 controls the thickness of the molten material 24 which is extruded from the slot 16 of the die 14. After the molten material 24 exits the slot 16 of the die 14 it is cooled by, for example, quenching in a bath of cooling water 26.
A wind-up roller 28, which is rotating as indicated by the 35 arrow 30 in Figure 1, collec~s the final elastomeric film product 20 which has a thic~ness that is 10ss than the ~.3~7'~

thickness of the freshly extruded molten material 24 due to the fact that the peripheral surface speed of the wind-up roller 28 is adjusted so that it is faster than the s~eed of extrusion of the molten material 24 from the die 14. As 5 a result of the fact that the peripheral surface speed of the wind-up roller 28 is greater than the speed of extrusion of the molten material 24, the molten material 24 is stretched, that is drawn down, as is known in the art, upon its exit from the slot 16 of the die 14. The drawing 10 down of the molten material 24 generally occurs after extrusion of the molten material 24 from the die 14 and prior to entry of the molten material 24 into the water bath 26 since the water bath 26 will cool and set the molten material 24 at the drawn down film dimensions. The 15 film 20 is transported within the water bath 26 by being passed under a plurality of transport rollers 32 and is then taken up on the roller 28.
Depending upon the rate of drawing down, the extrudable composition can be extruded as the molten 20 material 24 and then formed into elastomeric ~ilms having a thickness of not greater than about 25 mils, preferably having a thickness of not more than about 10 mils, for example, having a thickness o~ less than about 3 mils.

EXAMPLE I

A three component blend including (1) 60 percent, by weight, of an A-B-A' block copolymer having polystyrene ~A"
and ~AI n endblocks and a poly (ethylene-butylene) "B"
30 midblock (obtained from the Shell Chemical Company under the trade designation K~ATON GX 1657), (2) 30 percent, by weight, of a polyethylene (obtained from U.S.I. Chemical Company under the trade designation PE Na601) and (3) 10 percent, by weight, of a white concentrate of a colorant 35 blend of 50 percent, by weight, titanium dioxide and 50 percent, by weight, of a polypropylene obtained from _ ~3 _ ~3Q077~

Ampacet under the trade d2signation "White 41',1" was blended, at temperatures of from about 140 degrees Centigrade to a~out 210 degrees Centigrade in a Baker-~erkins compounding extruder arrangement including a 5 twin screw compounding extruder number 6000~ and a single screw extruder number 60020. The twin screw extruder was arranged to advance the compounded material to the single screw extruder from which strands of the compounded material were extruded, quenched with water, and chopped lO into segments to provide pellets of the compounded material.
The pellets were then fed and extruded through a 0.75 inch diameter Brabender extruder which had a length/diameter ratio of about 24:1 and had three 15 temperature control zones which were maintained at about 200 degrees Centigrade, about 215 degrees Centigrade and about 225 degrees Centigrade, respectively. After passing through the three temperature control zones, the compounded material was advanced to a film die which had a single 20 temperature control zone that was maintained at about 235 degrees Centigrade and had a die slot of about 4 inches in width and which, while no actual measurement was made, is believed to have been set at a gap, that is opening, of between about 25 and about 50 thousandths of an inch. The 25 compounded material was extxuded through the slot as a molten sheet. The molten sheet was drawn down, that is stretched, by the action of a wind-up roller to reduce its thickness and was then quenched (cooled) by being passed through a bath of cooling water. The thus-formed film was 30 collected on the wind-up roller. Due to the high tackiness of the film it tended to self-adhere and stick together.
Therefore, it was collected on the wind-up roller by interposing a sheet of silicone coated release paper between the adjacent film layers.

EXAMPLE II

A three component blend including (1) 70 percent, by weight, of an A-B-A' block copolymer having polystyrene "A"
5 and "A"' endblocks and a poly (ethylene-butylene) "B"
midblock (obtained from the Shell Chemical Company under the trade designation KRATON GX 1657), (2) 20 percent, by weight, of a polyethylene (obtained from U.S.I. Chemical Company under the trade designation PE Na601) and (3) 10 10 percent, by weight, of a white concentrate of a colorant blend of 50 percent, by weight, titanium dioxide and 50 percent, by weight, of a polypropylene obtained from Ampacet under the trade designation "White 41171" was blended, at temperatures of from about 140 degrees 15 Centigrade to about 210 degrees Centigrade in a Baker-Perkins compounding extr~der arrangement including a twin screw compounding extruder number 60009 and a single screw extruder number 60020. The twin screw extruder was arranged to advance the compounded material to the single 20 screw extruder from which strands of the compounded material were extruded, quenched with water ! and chopped into sesments to provide pellets of the compounded material.
The pellets were then fed and extruded through a 0.75 25 inch diameter ~rabender extruder which had a length/diameter ratio of about 24:1 and had three tempexature control zones which were maintained at about 200 degrees Centigrade, about 215 degrees Centigrade and about 225 degrees Centigrade, respectively. After passing 30 through the three temperature control zones, the compounded material was advanced to a film die which had a single temperature control zone that was maintained at about 235 degrees Centigrade and had a die slot of about 4 inches in width and which, while no actual measurement was made, is 35 believed to have been set at a gap, that is opening, of between about 25 and about 50 thousandths of an inch. The - 25 - ~3QV7~

compounded material was extruded through the slot as a molten sheet. The molten sheet was drawn down, that is stretched, by the action of a wind-up roller to reduce its thickness and was then quenched (cooled) by being passed 5 through a bath of water. The thus-formed film was collected on the wind-up roller. Due to the high tackiness of the film it tended to self adhere and stick together.
Therefore, it was collected on the wind-up roller by interposing a sheet of silicone coated release paper 10 between the adjacent film layers.
Films were successfully formed under the conditions stated in examples 1 and 2. However, during initial trial runs, the films were so tacky that they tended to self-adhere, i.e. stick together, and were not of a highly lS desirable uniformity as a result of surging of the material through the d~e. In an early attempt to overcome the surging problem, the procedures of example 1 were utilized except that the temperatures of the temperature control zones were each reduced by ten (10) degrees. This 20 reduction in temperature had no observable effect on the surging problem. One modiication that was observed as improving the ability to collect the film was to move the wind-up roller closer to the die so that the length of film which was passing through the water quenching (cooling) `~ 25 bath was reduced.
The films formed by the procedures of Examples 1 and 2 demonstrated elastomeric characteristics. In order to investiqate these elastomeric characteristics in both the machine direction (MD) and cross machine direction (CD or 30 TD) five one (1) inch wide (TD) by five (5) inch long (MD) samples were cut from the film for purposes of measuring the machine direction characteristics and five one (1) inch wide (MD) by greater than three (3) inches long (TD) samples were cut from the film to measure the transverse 35 machine direction characteristics. One (1) inch wide machine direction (MD) by five (5) inch long transverse - Z6 - 1 ~ O ~

direction ~TD) samples could not be obtalned because the width of the die slot and thus the maximum possi~le width of the film was only four (4) inches. Therefore, samples for measuring the transverse machine direction 5 characteristics of greater than three (3) inches long but less than four (4) inches long were obtained.
Each of the samples was placed lengthwise in an Instron Model 1122 tensile testex, having an initial jaw separation of three (3) inches, and was elongated, 10 stretched, to 50 percent elongation. That is, one and one-half its unstretched length. The load necessary to achieve this degree of elongation was measured and the sample was maintained at 50 percent elongation for one (1) minute and then the load necessary to maintain the S0 15 percent elonsation of the sample was measured. Next, the elongation of the sample was increased to 100 percent, that is, twice the unstretched length of the sample and the load necessary to achieve the 100 percent elongation was measured. The 100 percent elongation of the sample was 20 maintained for one (1) minute and the load necessary to maintain the 100 percent elongation was then measured.
Thereafter, the load was removed rom the sample for one ~1) minute and the percent of permanent deformation present in the sample after one (1) load free minute was measured~
25 The percent of permanent deformation after periods of three (3) and five (5) load free minutes were also measured.
Thereafter, the sample was elongated to break and the peak load encountered in elongating the sample to break and the percent of elonga~ion, a~ break, as a percent of the 30 unstretched length of the sample, were measured. The data obtained is reported below in Table III.

,...... . .

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) '-1 ` I

U~ Z X ~P dP d~
E~ O ~ ~ oco Z ~ ~ ~ ~ o o ~ ~ u~
c~ ~ m Z
o cr~ o ,~ ~n ~ ~ U

z o ~;
E~ ~ Z
~Z ~ ~ E~ ~`
~1 ~ ~1 C~ Z
~1 0 E-~ tl H
O :~
Z:
H ~ tL) ~S
O ~ a N ~ E ~ ~,~ E E 8 ~

U~ C ~ C ~ X ~ '-C ~ ~ U
æ c ~ ~ ~ o ~ v E~ ~ Q) u~ O .C t~ E~ S ~I E ~
1 H Ei ~ C: ~I C C~ C~ ~ O n~ h H ~ E ~ O ~ (O ~ ~ C au ~ v HdP H a! u7 ~o o ~ a) O ~ ~1 u~
,~ æ o E E E~
o~ z a) ~ 13 S

~ -- ~ ~ ~ o ~ a~ c ~ ~ S U~
o z E ~ u ~ ~ oO ~ U E ~3 ~
_ ~, h ~ 1 ~
~ l C U 3 z ~ e ~
1-~ 0 H ~U O O E3 C a~ C 3 ,¢ ~ ~ o .~ o~ iS O O
d~ ~ ^, o ~ ~ ~ ~ C ~ U ~:
O ~ ~ --~ ` ' ~ O U h ~ ~
H ^ ,~1 h O r~ a~ ta O X ~J rl 3 ~ E~ O~J ~1 0 ,~ ~ ` O h C a) ~ ~ O O
~A O `11~ h O S
~ ~ ~e u ~ u o ~ e au c~ o Z ~ 3 ~ S t/~ ~ Q G^ ~ ~ -~: ,4 ~ _, o ~ 3 ~ ~ C 6 a~ ~
O CS~ ~ o ~ O ~ C ~ 5 J
E~ 0 1111 11 11 ~: 5 E~
X

.

, .

~ 3~t~

Generally5 the elastomeric films of the present invention may also contain known useful additives such as pigments (such as the "White 41171"), plasticizers, antioxidants and the like in addition to the block copolymer and the polyolefin but these additives will usually be present in minor amounts of generally no more than about 15 percent or less, by weight, of the total weight of the film. Importantly, the formation of films of the invention is achieved without having to utilize materials which must be leached out of or otherwise removed from the films.
This case is one of a group of related Canadian patent applications of the applicant. The group includes application Serial No. 514,680, filed July 25, 1986 in the name of M.T.
Morman and entitled "Gathered Nonwoven Elastic Web"; application Serial No. 514,960, filed July 30, 1986 in the name of M.T.
Morman and T.~. Wisneski entitled "Polyolefin-Containing Ex-trudable Compositions and Methods for Their Formation Into Elastomeric Products"; application Serial No. 514,456, filed July 23, 1986 in the name of M.T. Morman and T.J. Wisneski entitled 20 "Elasticized Garment and Method of Malcing the Same"; application Serial No. 514~457~ filed July 23, 1986 in the name of M.T.
Morman and T.J. Wisneski entitled "High Temperature Method of Making Elastorneric Materials and Materials Obtained Thereby";
application Serial No. 514,423, filed July 22, 1986 in the name of M.J. Vander Wielen and ~.D. Taylor entitled "Composite Elastomeric Material and Process for Making the Same".

While the invention has been described in detail with respect to specific preferred embodiments thereof, it will be 30 appreciated that those skilled in the art, upon i , ~

~ ' ~

- 29 - ~3~f~

attaining an understanding of the foregoing, may readily conceive of alterationS to and variations of the preferred embodiments. Such alterations and variations are believed to fall within the scope and spirit of the invention and 5 the appended claims.

:`~ 10 ..

Claims (32)

1. An elastomeric film comprising:
from at least about 10 percent, by weight, of an A-B-A' block copolymer where "A" and "A'" are each a thermoplastic endblock which comprises a styrenic moiety and where "B" is an elastomeric poly (ethylene-butylene) midblock and from greater than 0 percent, by weight, up to about 90 percent, by weight, of a polyolefin which, when blended with the A-B-A' block copolymer and subjected to an effective combination of elevated temperature and elevated pressure conditions is adapted to be extruded, in blended form, with the A-B-A' block copolymer.

2. The elastomeric film according to claim 1, wherein the "A" and "A'" endblocks of the block copolymer are selected from the group consisting of polystyrene and polystyrene homologs.

3. The elastomeric film according to claim 2, wherein the "A" and "A'" endblocks of the block copolymer.
are identical.

4. The elastomeric film according to claim 2, wherein the "A" and "A'" endblocks of the block copolymer are selected from the group consisting of polystyrene and poly (alpha-methylstyrene).

5. The elastomeric film according to claim 1, wherein the polyolefin is selected from the group consisting of at least one polymer selected from the group consisting of polyethylene, polypropylene, polybutene, ethylene copolymers, propylene copolymers and butene copolymers.

6. The elastomeric film according to claim 5, wherein the polyolefin is a blend of two or more polymers selected from the group consisting of polyethylene, polypropylene, polybutene, ethylene copolymers, propylene copolymers and butene copolymers.

7. The elastomeric film according to claim 1, wherein the polyolefin is polyethylene.

8. The elastomeric film according to claim 7, wherein the polyethylene has a density of about 0.903 grams per cubic centimeter.

9. The elastomeric film according to claim 7, wherein the polyethylene has a Brookfield Viscosity cP at 150 degrees Centigrade of 8500 and at 190 degrees Centigrade of 3300 when measured in accordance with ASTM
D 3236, a number average molecular weight (Mn) of about 4,600, a weight average molecular weight (Mw) of about 22,400, a Z average molecular weight (Mz) of about 83,300 and a polydispersity (Mw/Mn) of about 4.87.

10. The elastomeric film according to claim 1, wherein the polyolefin is polypropylene.

11. The elastomeric film according to claim 10, wherein the polypropylene has a density of about 0.900 grams per cubic centimeter when measured in accordance with ASTM D 792.

12. The elastomeric film according to claim 11, wherein the polypropylene has a meltflow value obtained in accordance with ASTM D 1238, Condition L, of about 35 grams per ten minutes, a number average molecular weight (Mn) of about 40,100, a weight average molecular weight (Mw) of about 172,000, a Z average molecular weight of about 674,000 and a polydispersity (Mw/Mn) of about 4.29.

13. The elastomeric film according to claim 1, wherein the polyolefin is polybutene.

14. The elastomeric film according to claim 13, wherein the polybutene is an isobutylene-butene copolymer.

15. The elastomeric film according to claim 1, comprising from at least about 20 percent, by weight, to about 95 percent, by weight, of the A-B-A' block copolymer and from at least about 5 percent, by weight, to about 80 percent, by weight, of the polyolefin.

16. The elastomeric film according to claim 1, comprising from at least about 30 percent, by weight, to about 90, by weight, of the A-B-A' block copolymer and from at least about 10 percent, by weight, to about 70 percent, by weight, of the polyolefin.

17. The elastomeric film according to claim 1, comprising from at least 50 percent, by weight, to about 90 percent, by weight, of the A-B-A' block copolymer and from at least about 10 percent, by weight, to about 50 percent, by weight, of the polyolefin.

18. The elastomeric film according to claim 1, comprising from at least about 50 percent, by weight, to about 70 percent, by weight, of the A-B-A' block copolymer and from at least about 30 percent, by weight, to about 50 percent, by weight, of the polyolefin.

19. The elastomeric film according to claim 1, comprising about 60 percent, by weight, of the A-B-A' block copolymer and about 40 percent, by weight, of the polyolefin.

20. An elastomeric film comprising:
from at least about 10 percent, by weight, to about 90 percent, by weight, of an A-B-A' block copolymer where "A" and "A'" are each a thermoplastic polystyrene endblock, where "B" is an elastomeric poly (ehtylene-butylene) midblock and where the sum of the molecular weight of the "A" endblock with the molecular weight of the "A'" endblock is about 14 percent of the molecular weight of the A-B-A' block copolymer, and from at least about 10 percent, by weight, to about 90 percent, by weight, of a polyethylene having a density of about 0.903 grams per cubic centimeter which, when blended with the A-B-A' block copolymer and subjected to an effective combination of elevated temperature and elevated pressure conditions, is adapted to be extruded, in blended form, with the A-B-A' block copolymer.

21. An elastomeric film comprising:
from at least about 50 percent, by weight, to about 90 percent, by weight, of an A-B-A' block copolymer where "A" and "A'" are each a thermoplastic polystyrene endblock and where "B" is an elastomeric poly (ethylene-butylene) midblock, and from at least about 10 percent, by weight, to about 50 percent, by weight, of a polyethylene having a Brookfield Viscosity cP at 150 degrees Centigrade of 8500 and at 190 degrees Centigrade of 3300 when measured in accordance with ASTM D 3236 and a density of about 0.903 grams per cubic centimeter which, when blended with the A-B-A' block copolymer and subjected to an effective combination of elevated temperature and elevated pressure conditions, is adapted to be extruded, in blended form, with the A-B-A' block copolymer.

22. The elastomeric film according to claim 21, wherein the sum of the molecular weight of A with the molecular weight of A' is from about 14 percent to about 29 percent of the molecular weight of the A-B-A' block copolymer.

23. An elastomeric film consisting essentially of:
from at least about 50 percent, by weight, to about 90 percent, by weight, of an A-B-A' block copolymer where "A" and "A'" are each a thermoplastic polystyrene endblock and where "B" is an elastomeric poly (ethylene-butylene) midblock and from about 10 percent, by weight, to about 50 percent, by weight, of a polyethylene having a Brookfield Viscosity cP at 150 degrees Centigrade of 8500 and at 190 degrees Centigrade of 3300 when measured in accordance with ASTM D 3236 and a density of about 0.903 grams per cubic centimeter which, when blended with the A-B-A' block copolymer and subjected to an effective combination of elevated temperature and elevated pressure conditions, is adapted to be extruded, in blended form, with the A-B-A' block copolymer.

24. The elastomeric film according to claim 23, wherein the the sum of the molecular weight of A with the molecular weight of A' is from about 14 percent to about 29 percent of the molecular weight of the A-B-A' block copolymer.

25. A process for forming an elastomeric film from an extrudable composition comprising from at least about 10 percent, by weight, of an A-B-A' block copolymer where "A"
and "A'" are each a thermoplastic endblock which includes a styrenic moiety and where "B" is an elastomeric poly (ethylene-butylene) midblock, and from greater than 0 percent, by weight, to about 90 percent, by weight, of a polyolefin which, when blended with the A-B-A' block copolymer and subjected to an effective combination of elevated temperature and elevated pressure conditions, is adapted to be extruded, in blended form, with the A-B-A' block copolymer, said process including the steps of:
subjecting the extrudable composition to a combination of elevated temperature and elevated pressure conditions sufficient to effect extrusion of the extrudable composition from a film die as a molten film;
drawing the molten film to reduce the thickness of the molten film; and cooling the molten film by quenching.

26. The process according to claim 25, wherein the polyolefin is polyethylene. and the extrudable composition is subjected to an elevated temperature of at least about 125 degrees Centigrade to effect the extrusion of the extrudable composition from the film die.

27. The process according to claim 25, wherein the polyolefin is polypropylene and the extrudable composition is subjected to an elevated temperature of at least about 175 degrees Centigrade to effect the extrusion of the extrudable composition from the film die.

28. The process according to claim 25, wherein the extrudable composition is subjected to an elevated temperature of from at least about 290 degrees Centigrade to about 345 degrees Centigrade to effect extrusion of the extrudable composition from the film die.

29. The process according to claim 25, wherein the extrudable composition is subjected to an elevated temperature of from at least about 300 degrees Centigrade to about 335 degrees Centigrade to effect extrusion of the extrudable composition from the film die.

30. The process according to claim 25, wherein the film is drawn down to reduce the thickness of the film to less than about 25 mils.

31. The process according to claim 25, wherein the film is drawn to reduce the thickness of the film to less than about 10 mils.

32. The process according to claim 25, wherein the film is drawn to reduce the thickness of the film to less than about 3 mils.