CA1080559A

CA1080559A - Pressure-sensitive adhesive tape

Info

Publication number: CA1080559A
Application number: CA281,015A
Authority: CA
Inventors: Ralf Korpman
Original assignee: Johnson and Johnson
Current assignee: Johnson and Johnson
Priority date: 1976-06-23
Filing date: 1977-06-21
Publication date: 1980-07-01
Also published as: AU518205B2; IT1079059B; NZ184296A; JPS53235A; BR7704063A; AU2629277A; GB1559933A; DE2728346A1; PH13292A; NL190616B; ES459978A1; FR2355893A1; NL190616C; JPS6031233B2; NL7706854A; FR2355893B1; US4024312A; ZA773754B

Abstract

PRESSURE-SENSITIVE ADHESIVE TAPE

Abstract of Disclosure -- A highly conformable adhe-sive tape which comprises a highly extensible and elastic backing film laminated with an adhesive layer to form the tape. The adhesive is a normally tacky and prssure-sensi-tive elastomeric adhesive coated on at least one of the film surfaces. The film possesses a lengthwise elongation to break of at least about 200 percent, and a 50 percent rubber modulus of not above about 2,000 lbs./sq. inch. The tape is easily stretchable and normally may be removed easily from an application surface by stretching the tape lengthwise in a direction substantially parallel to the surface. This characteristic is highly important in medical applications where painless removal is desirable.

Description

The pr~ent lnvention relates to normally tacky and pressure-sensltive adhesive tapes, more particularly to such tapes which comprise a highly elastomerlc normally tacXy and pressure-sen ltive adhesive coated onto a basical-ly nontack~y backing film or sheet.

Prior art pressure-sensitive adhesive tapes of this type generally have had limited extensibillty and elas-ticity due to the properties of the backing sheetR employed.
In fact, tapes made with paper, foil~ or woven or nonwoven $abric backings have exhibited a low level of extensibility and virtually no elasticity although efforts have been made to incorporate extensibility by creping, or the like, and by impregnating papers and nonwovens with r~bbery binders.

. PLastic film-backed pressure-sensitive adhesive tapes have varied somewhat in properties dependlng upon the formulation and phgsical characteristics of the backing.
Highly plasticized films, for instance~ have had fairly high extensibility as compared w~th the unplasticized films. Both films however, have displayed a low order of elasticity.

I have invented a fiIm backed normally tacky and pressure-sensitive adhesive tape which is highly extensible and highly elastic and which normally may be remo~ed easily from an application surface by stretching it lengthwise in a direction ~ubstantiallg parallel to the plane of the sur-faceO

., ~

. 1080SS9 PL-239 The film backlng of my tape is formed from a unique film forming composition comprising elastomeric and thermoplastic A-B-A block copolymers, and the film pos~es~es a lengthwise elon~ation to break of at least about 2003 pre-~erably at least about 300~ percent and a 50 percent rubber modulus of not above about 2,000 lbs./ q. inch. This low rubber modulus appears to be an lmportant ~actor ln insuring easy stretchability and easy removal of the tape at high elongations. In ~act, in tapes used in absorbent dresslngs such as adhesive bandages, the thickness of the backing film is 3uch that when one end of the tape is stretched lengthwise as dèscribed above, the tape and dres~ing are removed without pain from the skin. This 'louchless't removal appears to be a function of both the high extensibility (elongation to break) and easy stretchability (low rubber modulus) of the film-adhe-sive lamlnate, as well as the thickness of the backing ~ilm and the laminate~

The elasticity of the bac~ing f~lm is important ~or conformability and othei purposes. Preferably, the film posses~es an elastic recovery from 50 percent stretch of at least about 75~, and more-preferably at least about 90%~ The backing fllm of this invention also is highly ~lexible and ~ "!
possesses a Gurley stiffness at a thickness o~ 1 mil of not above about one. A further advantage of the tape of th~s ln~
vention is that it remains flexible, extensible and elastic at very low temperatures and thus is highly advantageous for low temperature industrial applications.

p~-239 The backing fllm of my invention 1~ formed from an elastomeric and thermoplastic film forming compos~tion which comprise~ an elastomerlc component and 0-200 parts, preferably 85-200 parts of a resin component per one hun-dred parts by weight of the elastomeric component. The elastomeric component consist9 essentially of linear or radial A-B-A block copolymers wherein the A-blocks are thermoplastlc and the B-blocks are elastomeric, or mlxtures of these llnear or radial A-B-A block copolymers with simple thermoplastic elastomeric A-B block copolymers - In these block copolymers the A-blocks are derived from styrene or styrene h~mologues and the B-blocks are derived from con~u-gated dienes or lower alkenes. The proportion of A-B block copolymers in the mixture of A-B-A and A-B block copolymers should not exceed about 75 percent by weight and lower per-Centages normallg would be used. The resin component con-sists essentially of low molecular weight res~ns, pre~erably having a number average molecular weight not above about 3,000, and which are adapted to associate principally with the thermoplastic A-blocks of the sald block copolymers.

The A-B-A block copolymers of this invention are of the type which consist of A-blocks (end block~) derived, i.e., polymerized, from styrene or styrene homologues; and B-blocks (center blocks) derived from con~ugated dienes, such a~ isoprene or butadiene, or from lower alkenes, such as et~ylene and butylene. Small proportions- o~ other monomers also may enter into the block copolymer themselves. The indi-, vldual A-blocks have a number average molecular weight of at lea~t about 6,ooo, preferably in the range of about 8,ooo - 30,000, and the A-blocks con~titute about 5-5~ per-cent, pre~erably about 10-30 percent, by weight of the block copolymer. The number average molecular weight of the B-blocks for llnear A-B-A block copolymers preferably is in the ran6e of about 45,000 - 180,000 and that of the linear copolymer, itself, preferably 1s in the range of about 75,000 - 200,000.
The number average molecular weight of the rad~al A-B-A block copolymers preierably is ln the range of about 125,000 -400,000. The designation A-B-A includes what are sometimes - called A-B-C block copolymers wherein the end blocks are di~ferent from one another but both are derived from styrene homologues. This applies both to l~near and radial block copolymers.' The term "linear bloc~ copolymer" (or copolymers) includes branched A-B-A copolymers as well as unbranched A-B-A
copolymers.

' The radiaL A-B-A polymers useful in th~s inventlon ; ' are of the type described in United States Letters Patent No. ~ -3,281,383 and conform to the following general formula:
(A-B)nX, wherein A is a thermop}astic block polymerized from styrene or styrene homologues, B is an elastomeric block de-rived from con~ugated dienes or lower al~enes, as indicated above~ X is an organic or inorganic connecting molecule, with a functionality of 2-4 as described in Patent No. 3,281,383 or possibly with a higher functionality as described in the article entltled "New Rubber i9 Backed by Stars" appearing on page 35 o~ the June ll, 1975 issue of Chemical Week.
"n" then is a number corresponding to the functlonality of X

The A-~ block copolymers of this invention al~o are of the type wherein the A-blocks are derived ~rom sty-rene or styrene homologues and the B-blocks are derived from con~ugated dienes or polymers and copolymers derived from lower alkenes, either alone or in con~unction with small proportions of otker monomers. The A-B block copolymers are descrlbed in United Sta~es Letters Patent Nos. 3,519,58~ and 3,787,5~1.

The elastomeric component of the film formlng com-position oi this invention may include small amounts o~
other more conventional elastomers but these should not ex-ceed about 25 percent by weight of the elastomeric com~onent.
These other elastomers may include, highly broken down natu-ral rubbers and ~utadiene-styrene random copolymer rubbers,~yn-thetic'polyisoprene~ chloroprene-rubbers'~ nitrile rubbers~
butyl rubbers, and the like Potentially elastomeric liquid ~ ' polymers also may be employed as additives but normally in '~
lower proportions not above about lO percent by weight of the elastomeric component. ' -The resin component of the backing of this invention, if employed, consists essentially of low molecular weight re~
sins which are adapted to associate principally with, and are principally co~patlble with, the thermoplastic A-blocks of the said block copolymers. These include low molecular weight re-- ~ . ,,, , .- ' 108C)559 PL-239 sins based on poly-alpha-methylstyrene, polystyrene, poly-vinyl toluene and similar arom~tlc re~ins3 a~ well as copoly-mers thereof, coumarone indene and related cycllc compounds.
Preferred resins for this purpose possess a number average ~olecular weight not above about 3,000 although higher mole-cular welght resins in the low molecular welght range also mag be employed.

The film forming composition also may contain relatively small proportions of various other materials such as antioxidants, heat stabilizers and ultraviolet adsorbers, release agents, extenders, fillers and the like. Typical antioxidants are 2,5 ditertiary amyl hydroquinone and ~iter-tiary butyl cresol. Slmilarly, conventional heat stabili-zers such as the zinc salts of alkyl dithiocarbamates may be used. Lecithin is one release material which has been ~ ; -found to be partlcularly suitable in minor amounts in this type of extrudable particulate mixture. However, waxes and various other release agents or slip agents also may be added in this manner. Relatively small proportions, in the neighborhood of 25 parts by weight of the elastomeric compo-nent, o~ vario~s extenders such as higher molecular weight ; polystyrenes, nonreactive phenol-formaldehyde resins, linear polyester resins, polyethylene, polypropylene, etc., also may be included in the film forming composition of this in-vention. Similarly, the particul~te mixture of this inven-tion may include relatively small proportions, say 25 parts ; by weight of the elastomeric component, of fillers and pig-ments such as zinc oxide, aluminum hydrate, clay, calcium ~080559 carbonate, titanium dioxide, carbon black and others.
Many of these fillers and pi~ments also may be used in powdered form as parting agentq to be mixed with thermo-plastic elastomer particles to prevent these particles from agglomerating prior to blending with resin particleq and other materials.
The normally tacky and pre3qure-sensitive adhe-sive of this invention may be a conventional ela~tomeric rubber-reqin adheoive such as that disclosed in United States ~etters Patent No. 2,909,278. However, the adhesive, like the backing film, also may be based upon an A-B-A block co-polymer and therefore not only may be elastomeric but highly thermoplastic and extrudable. In this case the adhesive composition will include a tackifying resin which is adapted to associate principally with the elastomeric B-blocks of the block copolymer employed. Examples of such adhesives and tackifying resins are given in United States Letters Patent No. 3,676,202 -According to a broad aspect of the present invention, -there is provided a highly conformable adhesive tape which comprises a highly extensible and elastic backing film and a normally tacky and pressure-sensitive elastomeric adhesive layer on atleast one of the major surfaces of the film, said film being formed from an elastomeric and the plastic film forming composition which comprises an elastomeric component and 0-200 parts of a resin component per one hundred parts by weight of the elastomeric component, said elastomeric compo-nent consisting essentially of linear or radial A-B-A block copolymers or mixtures of these linear or radial A-B-A co-polymers with simple A-B block copolymers, said A-blocks being derived from styrene or styrene homologues and said B-blocks ~ - 8 -.

~08055'~

being derived from conjugated dienes or lower alkenes, æaidresin component consisting essentially of low molecular weight resins adapted to associate principally with the thermoplastic A-blocks of said block copolymers, and said film possessing: a. a lengthwise elongation to break of at least about 200 percent, b. a rubber modulus of not above about 2,000 pounds per square inch, and c. an elastic recovery from 50 percent stretch of at least about 75 percent, whereby the tape normally may be removed easily by stretching it lengthwise to separate the adhesive from the application sur-face. -other and further feature~ and advantages of the adhesive tape of this invention will appear to one skilled in the art from the following description, examples and claims, taken together with the drawings wherein:
~ igure 1 is a view in perspective of a roll or pressure-sensitive adhesive tape according to one embodiment ~-of this invention.
Figure 2 is a partial sectional view along the line

2-2 of Figure 1.

- 8a -i~.

: ' , .- - , . . . .

1~80559 p~-239 Figure 3 is a ~iew in perqpective of the tape of this invention a~ the tape is stretched longitudlnally for easy removal from an application surface.

Figure 4 i~ an enlarged broken sectional view taken along the line 4-4 of Figure 3.

Refexring to Fi~ures 1 and 2 of the drawings, there is shown a roll of normally tacky and pressure-sensi-tive adhesive tape 11 according to one embodiment of this invention which comprises a highly extensible and elastic backing fllm 12 and a pressure-sensitive adhesive layer 13 coated on one surface of the film. The opposite surface of the film 12 is coated with a release agent, not shown, to assure that the tape 11 will unwind readily after the tape is wound upon itself with the adhesive layer facing inwardly to form a tape roll, as shown in Figure 1.

Figures 3 and 4 ilIustrate an important property -of the tape of this invention, i.e~, its easy removal from an application surface. ~hen the tape 11 is applied to an appli-cation surface 14 as shown in Figures 3 and 4 with the adhe-sive layer 13 adhering to the surface, the tape of this inven-tion may be removed easlly from the surface by stretching the tape longitudinaily by a force applied to its end. The high extensibllity of the tape and its easy stretchability apparently cause the adhesive to release incrementally from the 3urface as the backing film begins to stretch substan tially at the first point oi contact with the surface. This first point of contact which can more properly be called the .
' :

~080559 PL-239 relesse point is Rhown at 15 ln Fi~ure 4 and, o~ course, i9 a ~unction of where the tape is adhered to the applica-tion surface. As this tape ls stretched in the direction lndicated.by the arrow the adheslve will release ~rom the appllcatio~ sur~ace at point 15 and t~e release point will move along the tape away from the direction of pulling as the adhesive releases incrementally ~rom the application ~ -sur~ace.

While the Qimplest ~orm o~ adhesive tape construc-10 . tion is shown in the drawings, it will be apparent to one skilled in the art that this invention em~races various other conventional pressure-sensitive adhesive tape con-structions. For instance, for many applieations, the tape may be marketed on a release liner such as a silicone coated paper. Diaper tapes, adhesive bandages, double-~aced tapes, etc.., normally use such silicone llners. The required re-lease properties ~or the tape construction shown in the draw-ings may be obtained by incorporating a slip agent into the backing film itsel~, as well as by coating a release agent onto the film as described above. .. ... .

The following examples of bac~ing films, adhesives and adheslve tapes according to this invention are given only by way o~ illustration and are not intended to limit the scope of the invention in any way.

~able A gives the film compositions for s~x backing ~ilms of this inventicn, i.e., Examples I-VI, together with the physical characteristics of the films. In these examples, 108~)559 PL-239 all proportlons are expressed in parts per one hundred parts by weight of the total elastomeric component of the fllm unless otherwice indicated.

Film thickness is expressed in ~ils, or thousands of an inch, tensile strength ln pounds per s~uare inch to break the film as measured on an Instron tensile tester with an initial ~aw separation of one inch at a speed of twelve inches per minute, and elongation ls the percentage which the film must be stretched in a gi~en direction to break it, i.e., stretched dimension at break minus normal dimension, o~er normal dimension in that direction, times a hundred. In all c&ses the designation "M.D.rl means "machine direction" lengthwise in the direction of process-ing and "C.D.'r means 'Icross direction.'l Elastic recovery is percentage of immediate re-covery in length after being stretched fifty (50) percent of original length and then released to allow free return.
- It i3 a functlon of the amount of stretch recovered over - the amount of stretch. The amount of stretch equals the length when stretched minus the original length and the amount of stretch recovered equals the length when stretched minus the length after recovery. Rubber modulus is tensile stress in pounds per square inch of initial cross section j measured at one half inch extension per inch o~ length or 50 percent elongation. This also is called 50 percent rubber modulus.
Gurley stiffness is measured as an opposite or inverse measure of flexibility with a standard Gurley stiff-ness tester using 1.0 by 1 5 inch samples with 1/4 inch of . :, , , :

108~559 PL-239 sample ln the ~aw and 1/4 inch overlapping the blade. The measured Gurley stiffnes3 then is converted to sti~fne3s at a thickness of one mil by di~iding the measured stiff-ness by the cube of the measured thickness in mils.

~eat sealability is measured by clamping each film sample in an open sandwich with a sheet of standard iiberboard test material between the ~aws of an Erich International Corporation Bag Sealer at 42 p.9.i. air pres-sure. The fiberboard is Standard Reference Material 1810 speci~ied in United States Department of Commerce Standard for Tape Adhesion Testing No. 16 (M:L-B-131E, Class 2).
One of the ~aws is heated and the other i9 unhea~ed. The boxboard is placed in contact with the heated ~aw and the fi}m in contact with the unheated Jaw. Both ~aws are cooled to amblent temperature by air ~ets-prior to clamping. When the test material is in position between the ~aws, the bot-tom Jaw is heated by an electric heater to seal the film - to the boxboard by heat transferred through the board. The heating tlme period re~uired to heat the lower ~aw to the minimum peak temperature neceasary to permanently heat seal the film to the boxboard, using a clamping period of 4 sec-onds~ then is measured. The minimum peak permanent heat sealing temperature correspond~ng to the time recorded, then is obtained by reference to a time-temperature calibra-tion cur~e for the instrument obtair.ed by measuring tempera-tures ~t the bonding surface of the boxboard. The minimum peak temperature refe~red to is that reached at the time the electric heater is deenergized at the end of the heating ti~e period.

~080559 o o o o t~ ~ N ~ O O d ' ~ t`~ -~1 ~ ~ . o ~ o ~q O O
~ O O ~ ~ U~ O ~ O
_I ~1 0 0 ~ ~ ~ I O 1`
~ ~ d' ~ o -, ~ Ul O o ~ u~ O o o o or~
~ O O ~ O
H ~1 ~1 _I ) d'U~ ~ I` ~`O

H I O O t`~ ~ O O O N Ir) H I O O . ~ O ~ Irl ~ O
H ¦ ~1 _I r-l~) OD n 1`~1 ~1 o U~ O O O O
o 1s) ~ 1~~`1 O N Ct) H I O ~ 1 O d'0 H I ~1 r-l ~I d'~I t` _I ~_I O

O O ~(~'l U') O O O O
'I ~ d'd~ ~) u) t~
~¢ H I _~ ~1 ~1 ~1~1 u~ 1` C~11~ 0 r~
~ _ , ~

~: X C~
O r~
.,~ ~ .
X ,~ ~ :
. ~ .C .~:
u~ Q Q~4 -- Q O ~ ~ ~1 -. ~ U n~ G
O ~ G ::
1~1 ~ $
u ~ a ~ ~ O ~ o I I H Ul bqbq ~ El ^ ^ ~ ~ n U~ H m I nw nwa) r~w ~ ~nw U~
J~ I I ~ a a ~ OOOOX 5~X
.,, ,~ ~ ~ ~ o ~ ~_I ~ o--_I _ _ a.) aJ q J
O O
t~ o ~ ~ ~ .Q O O u~
~ ~I X X U') ,5~ ;E; r/ ~ nw 1:~ ~t * ~ a)a) ~rl ~) ~nW ~ ~ a) c~ ,,,, H C ~ w * ~~) K a r~
O O ~ O O 0 ~ wt5~ w~ rl ~4 0 U O (~U 1~ 0 R
0 U O ~ ,L2 0 0 ~ n~
~ ~ U N ~ E~
m 1~ - 13 -. .
, H ~
.
. t7 O
_1 t ~3-8 ~ ~ oD

H O
H u~ 0 H t`~ ~

Ul O
H, O
Ir~

O
d ~q U
~1 O
~1 ~q ~
~
~ o a u~
u l h ~ ~ ~
~ ~ ~ .

~ ~ U
~1 ~ a~
~:5 ..
~ -~ U
H U~
a) 1 3a -10 80 55g PL-239 It will be seen that the films of all of the abo~e examples are quite elastic, i.e., posses~ an elastic recovery a~ter 50 percent elongation of about 80 percent or more and generally well above 90 percent. In fact, all the ~ilms of the examples have an elastic recovery of over 90 percent except ~or those formulated with the Piccotex poly-alpha-methylstyrene-vinyl toluene resins. Furthermore, all the films possess a low rubber modulus, i.e., below about 2,000 lbs./in. at 50 percent elongation and all but one have a modulus at 50~ elongatlon of not above about 1,000 lbs./in.2.

The films of the examples are not particularly oriented as evidenced from the tensile strength readings in the machlne and cros~-directions and generally possess a high elongation, i.e., at least about 500 percent in both direc-tion~ In fact, there are only two readings below 500 per-cent and these are well above 300 percent~

The films are highly flexible, exhibiting Gurley stif~ness readings as low as 0.2 mg./in.2/mil and no higher than 0.75 mg./ln.2/mil. The maximum permanent heat sealing temperature determined as described hereinbefore ranges between 150F. and 2800F., well below 350F.

TabIe B gives the compositions of three adhesives useful in the pressure-sensitive adhesive tapes of this in-vention. These are the:compositions o~ Examples VII - IX.
All proportions are expressed in parts per one hundred parts by weight o~ the total elastomers in the adhesive composi-tions.

?08~559 PL-239 TABLE B

Ingredients Examples VII VIII IX

Kraton 1107 S-I-S Linear Copolymer 100 40 Solprene 311X S-I Simple Copolymer 60 Raw Natural Rubber 100 Wingtack 95 Tackifier Resin 80 60 DehydrQgenated Rosin Tackifler Resln 85 Particulate Sillca 10 Lanolin 25 Titanium Dioxide 60 Zinc D~butyl Dithiocarba~ate 2 2 . 2 2,5 Di~srti~ry Amyl Hydroquinone 0.5 0.5 0~5 _ .. .

In Examples X - XV, normally tac~y and pressure-sensitlve adhesive tapes of this invention are produced first by coating one ma~or ~urface of each of the fllms of Examples I - Vl with the release agent of x~mple III of United State~ Letters Patent No. 3,502,497, then by apply-ing selected adhesive3 of Example~ VII - IX to the other ma~or surface o~ the film~ as described hereina~ter. Due to the solvent sensitivity and elastic nature of the back-ing, special techniques should be used for coating and slitting the tape. A pre~erred method is to co~t and dry, or extrude, the adhesive onto an nonelastic carrier such as a silicone coated release paper and laminate the film packing to the adhesive, preferably while the adhesive is still hot. The laminated tape with the carrier paper may be slit and used in th~s form either in strips or rolls or the tape may be rolled into log rolls without stretching a~ the liner is removed. ~og roll~ are normally slit on a lathe using an indexing knive which slits one roll at a time ~rom the log roll to form tape rolls with the adhesive layer ~acing inwardly as shown ~n Figure 1 o~ the drawings.

-~osasss The followlng Table C shows the appllcatlon of the adheslve compositions to the release coated backing films of these examples.

TABLE C
Element Examples X XIXII ~III xrv XV
Bac~ing Films I II III IV V VI
Adhesi~e VII VII ~II VII VIII IX -In examples X- XII the adhesi~e is coated onto the backing from a solution o~ 50 percent solids in toluene and then dried to remo~e the toluene before slitting. In Examples XIII and XIV the adhesive is extruded hot onto a silicon coated paper release liner and then tran~ferred to the backing film after cooling and before slitting. The adhesive of Examplo XV is coabed from 30 percent solids in toluene, dried and slit as described hereinbefore. Each Or the resultlng normally tacky and pressure-sensitive ad-hesive tapes of Examples X - XV is highly conformable and ~lexible even at ver~ low temperatures, and is highly ex-tensible, eas~ly stretchable and elastic as i~dicated here-lnb~fore. These tapes are removable easily from application sur~aces merely by stretching them substantially in the di~ection of their length, and when applied to the human skin provide painless or "ouchless" remo~al in the same way.
In the foregoing examples Kraton 1107 copol~mer is a thermoplastic elastomeric A-B-A (st~rene-i~oprene-~080559 PL-239 ~tyrene) blo~k copolymer of this invention offered by the Shell Chemical Company, wherein the styrene content (that of the A-blocks) is about }2-15 percent, closer to 15 per- -cent by weight o~ the block copolymer, and the polymer posses~e~ a solution viscosity of about 2,00~ centipoises at 25 percent solids in toluene at room temperature tusing a.~rook n eld Viscometer with a ~o~ 4 spindle at 60 r.p_m.)J
and a number a~ersge molecular weight of about 110,000 -125,0.00. Kraton 1102 cop~lymer is another A-B-A block copolymer offered by Shell but this is a styrene-butadiene-; styrene copolymer wherein the styrene bloc~s constitute about 30 percent of the-copolymer. The number average mole-cul~-r weight of Eraton 1102 copolymer also ls about 12~,000.

Solprene 420 copolymer i~ a radial styrene-isoprene-styrene block copolymer of the type described hereinbefore whic~ has a number a~erage molecular weight of 240,000 and a styrene content of about 15 p~rcent. Solprene 311X i~ a simpla A-B (styrene-isoprene) block copolymer having 15 per-cent styrene. Both Solprenes ar.e offered by Phillips Petroleum.Company.

Cumar 509 LX resin ~8 a sol~d coumarone indene re-sin of~ered by the Neville Chemical Company, and having a ~oftening point o~ about 145C. Amoco 18-290 resin is a solid poly-alpha-methylstyrene o~fered by Amoco Chemical Com-25 pany, with a so~tening point of about 290F. (143C.).
Piccotex lQ0 and 120 resins are pol~-alpha-methylstyrene-~inyl toluene copolymers offered by Hercules Chemical Company, with melting points of 100C. and 120C., respectively.

-18_ Wingtack* 95 tackifier resin is a solid tackifier resin consisting predominantly of polymerized structures derived from piperylene and isoprene, with the ratio of piperylene to isoprene derived structures being at least about ~ or 9 to 1, and with the remainder being derived from mono-olefins. It appears to contain about 12-15 per-cent unsaturation based upon percentage of units in each molecule having a double bond. The said resin is polymerized from a stream of aliphatic petroleum derivatives in the form of dienes and mono-olefins having 5 or 6 carbon atoms all in accordance with the general teachings of the aforesaid United States Letters Patent No. 3,577,398. This resin possesses a softening point of about 95C. by the ball and ring method, a number average molecular weight of about 1,100 and is offered commercially by Goodyear Tire and Rubber Company.
Having now described the invention in specific detail and exemplified the manner in which it may be carried into practice, it will be readily apparent to those skilled in the art that innumerable variations, applications, modi-fications, and extensions of the basic principles involvedmay be made without departing from its spirit or scope.

*Registered Trademark B

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A highly conformable adhesive tape which com-prises a highly extensible and elastic backing film and a normally tacky and pressure-sensitive elastomeric adhesive layer on a least one of the major surfaces of the film, said film being formed from an elastomeric and thermoplastic film forming composition which comprises an elastomeric component and 0-200 parts of a resin component per one hundred parts by weight of the elastomeric component, said elastomeric compo-nent consisting essentially of linear or radial A-B-A block copolymers or mixtures of these linear or radial A-B-A copoly-mers with simple A-B block copolymers, said A-blocks being de-rived from styrene or styrene homologues and said B-blocks being derived from conjugated dienes or lower alkenes, said resin component consisting essentially of low molecular weight resins adapted to associate principally with the thermoplastic A-blocks of said block copolymers, and said film possessing:
a. a lengthwise elongation to break of at least about 200 percent, b. a rubber modulus of not above about 2,000 pounds per square inch, and c. an elastic recovery from 50 percent stretch of at least about 75 percent, whereby the tape normally may be removed easily by stretching it lengthwise to separate the adhesive from the application surface.

2. An adhesive tape according to Claim 1, wherein the film possesses an elastic recovery from 50 percent stretch of at least about 90 percent.

3. An adhesive tape according to Claim 1, wherein the backing film possesses a Gurley stiffness at a thickness of 1 mil or not above about one.

4. An adhesive tape according to Claim 1, wherein the proportion of the A-B block copolymers in the mixture of A-B-A and A-B block copolymers is not above about 75 percent by weight.

5. A highly conformable adhesive tape which comprises a highly extensible and elastic backing film and a normally tacky and pressure-sensitive elastomeric adhesive layer on at least one of the major surfaces of the film; said film being formed from an elastomeric and thermoplastic film forming composition which comprises an elastomeric component and 85-200 parts of a resin compo-nent per one hundred parts by weight of the elastomeric component, said elastomeric component consisting essentially of linear or radial A-B-A block copolymers or mixtures of these linear or radial A-B-A copolymers with simple A-B block copolymers, said A-blocks being derived from styrene or sty-rene homologues and said B-blocks being derived from conju-gated dienes or lower alkenes, said resin component consist-ing essentially of low molecular weight resins adapted to associate principally with the thermoplastic A-blocks of said block copolymers, and said film possessing:
a. a lengthwise elongation to break of at least about 200 percent, b. a rubber modulus of not above about 2,000 pounds per square inch, and c. an elastic recovery from 50 percent stretch of at least about 75 percent, whereby the tape normally may be removed easily by stretch-ing it lengthwise to separate the adhesive from the applica-tion surface.