CA2126982A1

CA2126982A1 - Removable, low melt viscosity acrylic pressure sensitive adhesives

Info

Publication number: CA2126982A1
Application number: CA002126982A
Authority: CA
Inventors: Albert I. Everaerts; Jeffrey D. Malmer
Original assignee: Individual
Current assignee: 3M Co
Priority date: 1991-12-31
Filing date: 1992-12-18
Publication date: 1993-07-08
Also published as: AU665606B2; JPH07502560A; NO942460L; EP0619830B1; CN1073962A; BR9207011A; US5552451A; JPH07502558A; ES2092806T3; AU3278493A; KR100270155B1; DE69214163T2; DE69214163D1; US5648425A; DE69214164D1; EP0619830A1; TW221061B; BR9206999A; NO942461L; WO1993013148A1

Abstract

The present invention relates to a permanently removable, low melt viscosity acrylic pressure-sensitive adhesive comprising a lower alkylacrylate, a higher alkylacrylate and a crosslinker.

Description

"3~ 7 2~6~ '. rcT/us92/~0776 ~:MOVABI~E :, LOW MELT VI SCOS I TY
ACRYLIr P~:SSURE SENSITIVE AD~EESIVES

Field of Invention --The preaent invention relates to a pe~manently removable, low melt visco3ity acrylic pressure-sen~itive adhesive. In - ~ -partlcular, the pr~sent lnvention relateff to an adhesive comprising a lower alkyl acrylate, a higher alkyl acrylate and a cros~linker.
~ac~rQund of th~ Inven~l~n Removable pro~aur~ sensit~Ye adhe~ive~ (PSA) adhered to a -~
backing, which predictably adhere, yet remaln repeatedly peelable from a varLety of ~ub~trates over a long period of time without damaging o~ marring the substrate, have many commercial uae~. For example, ma~king tapee, removable labels or of~ice notes, protectlve film~ and medical tapes all must quickly aclhere to metal, paper, plastic~ and skin, respectively, but mu~t al~o peel smoothly away from these varied ~ub~trate~ without leaving behind ~ ;
any adhesive residue on or damaging the ~urface of a particular aubatrate.
Ideally, depanding on the ~ub~trate, the removable adhesLve mu~t provide ~ufficlent tack ~or quick ~tick) to quickly fix the adhe~ive to the de~ired subatrate, adequate peel strength to prevent damage of the surface when the adhesive i~ removed, and 25 have the appropr~ate ~ohesive ctrength to control the tran~fer of ~-adhesive tv the ~ub~trate. Cohe~ive strength mu~t also be --~
controlled BO to limit tha cold flow of the adhesive on a surface, a process which leads to an unde~irable building of peel ~trength over time. Balanc~ng ths~e pres~ure ~ensitive adhe~ive ;~
prop2rties, particularly Ln a removable adheaive, pose~
difficultie2 to the formulator.
U.S. Patent No. 3,691,140 5$ilver~ disclo~e~ the u~e of solid, inherently tac~yt pressure-~ensitiv~ adhe~i~e micro~here~ ~ -which, when adhered to a ~r~t subetrate, may when contacted to a nacond ~ubstrate be ea~ily rem~ved from the second Yubatrat0 wlthout del~mlnating th~ f~ret ~ub~trate or the seco~d substrate.
While ~xh~bitlng a high degr~e of removab~llty, microsph~re adhesive~ tend to transfer to ccntact surfaces ~uch the second ~ubstrate.
U.S. ~atent No. 5,045,569 ~Delgado) di~clo~e~ hollQw, inherently tacky pres~ure-een~itive adhe~ive acrylate microspheres which, due to ~heir unique morphology, provide enhanced pe~l~and ~hear strangth and le~8 adhe~i~e tranefer to ~ubBtrate~ than ~repositionabl~ adhesive~ based on ~olid acrylate-based ~,,.

~ ,"',',."

W ~ ~tl~lq7 PC~/US~2/10776 2'~ 2 6 9 3 ~ - 2 -mlcro~phere~. Althou~h hollow m~cr~sphere adhe0Lves ~how le adhoelve tran~fer to ~ub~trst~n, they ~tLll have le~ than an optimum degree of adhesivæ transfer.
In contra~t, U.S. Patent No. 4,599,265 (E~may) d~cloReR an adhesive having a high degree of cohesive ~trength. The adhesive discloe2~ ie an acrylate, ha~ low tack and maintain~ pe~lability from a varlety of ordinary substrate~. Esmay t~achee that through the cro~linklng of the tape'~ adhesive layer and the uBe of low level~ of polar monomer ~up to mole 3% of a etrongly polar monomer, ~uch as acrylic acid~ along with alkyl acrylates having ~de chain3 8-12 carbon~ in len~th in the copolymeric adhesive, the required balance of low tack and high cohe~ive strength can be - --~imparted to th8 removable adhe~ive. One drawbac~ a~ociated with `~-:
the E~may adhe~iv~ i~ excessive adhe~ve bleeding of monomer~
through a ~ubstrate ~uch aB pap4r prior to cur$ng. Such bleeding i~ unde~lrable because of the damage done to the substrate.
U.S. Patent ~o. 4,737,559 (Kallen et al.) de0crLbes another method of cro0~1lnking an adheeive. Kellen et al. teaches the use of a PSA formulation in which the viscous flow, and re~ultant ad~eslon buildup, is controlled through the addition of amall amount of a free radi~ally polymeri2able photocro~elinker ~a mono-ethylenically un~aturated aromatic ketone, mo~t preerably 4-acryloyl-oxy-benzophenone) to at least one alkyl acrylate or m~thacrylate. The Kellen et al. adhe~ive i~ formulated for adhes1on to ~kin.
U.S. Patent No. 3,635,754 (~eede) clisclose~ the u~e of a heat-activated, multi-phase pres~ure-sensitlve adhesive copolymer who~e melting point iB greater than 35C and who~e gla~
tran~it;on emperature (Tg~ iB below 5C. At room temperature, the adhe~ve i~ non-tacky. At that temperature, a crystalline or ordered pha~e and an amorphous or disordered pha~e co-exi~t. At ~kin temperature (approximately 35~C), the copolymer becomes amorphou~ and the adhe~ive i~ tac~y. This phenomenon may be ravex~ed by coolln~ the adhe~ive for removal from a ~ub~trate, ~-35 with the cryBta~ ation o~ ~he B~de chain~ provLding ~ufficient~ ~
coheBive strength to preve~t any tran~fer of adhesive to the ~;
~ubstrate. : ;
European Patent Application Ser~al Number 9O/134~0 (Stewart et al ) dihclo~e~ a temperature activated, pxe~ure-~ensitive adhesive which ie rapidly converted rom non-tacky to tacky over a predet~rmined temperature range. Simllax to the multi-pha~e ~ `~
adhe~ive of ~eQdQ, thl~ te~npar~ture dep~rldent adh~al~e r~lLe~ on the careful ~elec~clon o ~ide chain cry~talllzable monamers, partlcularly tllose monomers which hav~ l~near allphatlc side w~ ~"~ 2 ~ cr/us~ ()77~
~ 3 -chaln~ of at least 10 carbon atom~, includlng cl2-c22 alkyl acrylate~ or methacrylates. Stewart ~t al. speclfy that these compositions, when a mixture of copolymerizable monomers are u~ed, must contAln at lea~t 503 by welght monomera wlth cryatall~zable aide chain~. However, at room temperaturQ, these adhesLve~ are substantially non-tacky.
In usin~ PSA~, lt L~ al~o de~irable to combine these removable qualities wlth the procedural, economic~l and en~ironmantal ~dvantages of a hot melt proce~slble adhesive. To date, most attempts to prepare acrylic hot melt PSAs have been limited becauee such material~ have poor cohe~ive strQngth at room temperature or are to~ viscoua even for uae at high temperature~ -found in current melt proceasing equipment and practices.
Maintaining sufficient cohe~ive ~tr~ngth, a~ noted above, is one critical factor in t;he formulation of permanently removable PSAs.
Typically, the cohe~ive strength of acrylic polymeric PSAs, whlch are not mlcrospheres, may be improvecl in a vari~ty of ways, but each way has its diaadvantagea, aspecially when the formulator wishes to maintain a low melt vi~cosity for the PS~. The molecular welght of the acrylic polymer may be rai~ed to improve cohes$ve strength, but an unavoidable and unacceptable rise in melt viaco0ity aleo re~ulta. Polar monomer content, such a~
acrylic acid, may ~l~o be $ncr~a~ed to improve coheaive strength, a property wh~ch ~ B u~eful in many adh~sLve applicatLone.
25 However, increased polar monomer content also cau~es greater ~ ~;
adheslon buildup, as deacribed by U.S. Patent No. 3,008,850 ~Ulrich). Finally, cohe~ive ~tr~ngth may be enhanced through the covalent cro~lin~ing of the adhesive. Covalent cro~linking, though providing the needed increa~e in c~hesive strength, `
elimin~tes the potential for melt proc~s~lng.
PhysLcal cro~slinking i~ d~0cribed in U.S. Patent N~
4,554,324 (H~man et al.). Husman et al. di~cloYe a hot melt -processible acrylats PSA which gain~ the needed balance of ;~
cohe~ve ~trength, h~gh tack, and low melt viaco~ity through the 3~ chemical modLfica~ion of the ~oft acrylata backbons by grafting re~nforc~ng h~gh Tg polymeric moLet~ to the acrylata chain.
The~e hi~h Tg mo~et~e~ prov~de 9laB~y domain~ which enhance the ~ ;
coheaive strength of the adheai~e at lower te~perature~ without dramatically increa~ng the melt V~BC08ity of tha compo~ition.
Th~ pe81 adhe~ion atrength~ of the exemplified compounds, ho~ever, tend to excead tho~e values wh~ch are req~red for removabilLty ;~
from mo~t ~ubstrates.

''.'' '.- '. '' '' ,' '"' WO ~ 7 PCr/US~2/1077 ~C~J6~ 4 -Thu~, there curr~ntly exiet~ a need for a permanently removable acrylic pre~0ure censiti~e a~he~ive which dieplays a ~uperlor balance of tack, peel ~trQngth and cohe~lve ~trength which may be formulated for removal from a varlety of ~ubstrates without dama~ing or depo~lting adhe~ive re~idue on the ~ub~tate and wlthout building exce~ively in adhesion over time.

Su~marv of the Inventlon Unle~u otherwi~e noted, the t~rm ~acrylate~ i~ Lntended to -.
refer to methacrylatee in addition to acrylates.
The permanently removable, acrylic pres~ure-~en~itive adhe~lve of the lnvention comprieess a) from about lO to about 50 ~ by welght of at le~t one hlqher alkyl acrylate having an alkyl group from 12 to 26 carbon lS atome;
b) from about 50 to about 90 % by weight of at least one lower alkyl acrylate havlng an alkyl group from 4 to 12 atoms wherein ~aid upper and lower alkyl acrylate~ cannot ~imultaneously ha~e alkyl chain~ of 12 carbon atoms; and c) ~uff~cicnt cro~sllnker to impart: enough cohe~i~e strength to the adhe~ve ln order to prevent ~ub~tant~al adho~ive transfer.
In one ~mbodim~nt of the pre~ent invention, the lower alkyl acrylate ha~ an alkyl group which i~ linear a~d ha~
from 4 to 8 carbon atom~.
In another embodiment of the preaent invention, the lower alkyl acrylate ha~ an alkyl group which is branched and has from 4 to 12 carbon atoms.
In ~ preferred embodiment of the pre3ent lnvention, the high 30 alkyl acryl~to ha~ a carbon group which 1~ branched and ha~ from ~:
13 to 26 carbon atoms.
Thl~ lnv~ntion also provide~ for pres~ure-sensltive adhe~ive ~. ~
~heets csated with the permanent~y removable, acrylic adheslve . :
composition~
Further, th~ pre~ant invention disclose~ method~ of making adh~sive coating sheet~ with the acrylic adhesive compo~lt~on o ` th~ pre~ont invent~on.

The permanently r~moYable, lvw mslt vi~co~ity ~cryl~c pra~sur~-~sn~itl~e ~dhes~v~ of th~ invantlon comprise~ ~hr~e co~ponent~: ~l) at l~a~t one lower alkyl acrylate having an alkyl group whlch ~ompri~ fro~ ~bout 4 to l2 cArbon atom~7 ~2~ at ~:
lea~t one h~gh~r alkyl acrylat~ havin~ an alkyl group whlch ~V~ 17 P~r/us~2/ l077 ~ 5 ~ % L 2 6 ~S~
compr~0~ from abo~t 12 ~o 26 carbon atom~ nnd ~3) ~ufficlent cro~alinker to ~mpart cohe~ve ~trength to the adhesive.
The linear or branched lower alkyl acrylate or methacrylate `
e0ters u~eful ln preparLng the removable, low melt viscosity presaure ~en~itive adh~sivs~ of thi~ inventlon are linear or branched monofunctlonal unsaturated acrylate or methacrylate esters of non-tertiary alkyl alcohola, the alkyl group3 of which ha~e from about 4 to about 12 carbon atoma. The~e lower linear and branched acrylate~, a~ i~ well known in the pres~ure ~eneitiv~
adheulve art, provide the ~ropertiee of low glaes tran~ition temp4rature and vi~coela~tic characteristic3 that reeult in materials which are tacky in nature. Ex~mple~ of the 0horter chain, lower alkyl acrylate~ and methacrylates u~ed in the inventLon include, but are not limited to, n-butyl acrylatet -~
lsobutyl acrylate, 2-ethylhexyl acrylate, Leooctyl acrylate, n-octyl acrylate, n-octyl methacrylate, 2-methylbutyl acrylate, l~ononyl acrylate, ~80amyl acrylate, ~sodacyi acrylate, l~odecyl methacrylate, 4-msthyl 2-pentyl acrylate, and mixtur~ thereof. : -Preferred lower acrylate and methacrylate esters of the lnvention include ieooctyl acrylato, n-butyl acrylate, and 2-ethylhexyl acrylat0.
The hlgher alkyl acrylate or methacrylate monomer~ u~eful in preparing the pre~aure sensitive adhe~lves of thi~ lnvent~on are monofunctional uneaturated acrylate or methacrylate esters of non-tertLary alkyl alcohol~, the alkyl groups of which have from about 12 to about 26 carbon atoms. Preferably, the alkyl group~ : ~
have from about 13 t~ about 26 carbon atome. The lonq 3ide chains ---of these acrylate and methacrylate e~ters increa~e ~he entanglement molecular we~ght of the polymer and facilitate the -~
30 melt proce~ing of the polymer. At the concentratLon~ u~ed in -this invsnt~on, no cry~tallization of the ~id~ chains occurs and the re3ulting polymer~ are amorphous. I sub6tantLal crystallization were prs~ent, the modulus of the material would increase and thi3 increa~ed modulus would cau~e a loe~ of pres~ure sensit~ve adhe~Ye tack. The long alkyl chains of the~e acrylate and methacrylat~ e~ter~ al~o lncrease the non-polar character of `~
the adh~siv~, thue reduc~ng the ~ps~flc inter-moleculax int2ract~0n~, ~uGh as hydr~gen bonding, acid-base interaction, and ;
the like, which lead to exse~a~v- adhe3ion build-up betwe~n the ~ d adhesives and eubstr3te~ ~u~oeptible to ~uch interaction~
Examples of the long side ohaLn acrylate and methacrylate est~r~ u~ed in the pre~ent inve~tion include, but are not limited to, lauryl acrylate9 lauryl metha~rylate, i~ot~ldacyl ~crylate, n-tetradecyl acrylate, n-tetradecyl methacrylate, n-hexadecyl ', -' '',.

. .
,.3 ~', ' ','".'~',,, ",'"-,~

W ~ 47 ~Cr/u~)2/l~776 ~ ~ '1.,6~ '~ ' 6 -~cry ~e, n-hexadecyl methacrylate, n-octadecyl acrylatn, n-octad~cyl methacrylate, elcosanyl acrylate, hexacosanyl acrylate and mix~urn~ thereof. Preferrad long ~ide chaln a~kyl acrylate~
and methacrylates include lauryl acrylate, lauryl mothacrylate, octad~cyl acrylate, octad~cyl m~thacrylat~, hexaco~anyl acrylate, eicosanyl acrylate and ~eotridecyl acrylate.
Cros~linkers which enhance the cohesive ~trength of the removable pre~ure sen~ltive adh~ive compo~ition, include, but are not limlted to: multifunctional acrylates and methacrylatee;
trlazine-, benzophenone- and acetophenon~- derived photocro~linking compound~; znd silane~.
Pref~rred cro~slinkers are ~elected according to the procsa~ing method u~ed in preparing the adhe~ves of thi~
in~ention. For compositions which require no further melt processln~ following the initial polymerization, multlfunctional acrylate~ and methacrylate~, ~uch as 1,4butancdlol diacrylate and 1,6-hexanediol diacrylate can be ueed a~ cros~linkers. Additional poly~unctional acrylic monomera which can be u~ed a~ cro~slLnker~
in tho present invention are disclosed in U.S. Pat~nt No.

4,379,201 ~Hellmann et al.), wh~ch iB incorporated herein by reference.
Chromophore-sub~tltuted halomethyl-s-triazine~, ~uch aB
tho~e d~scribed by U.S. Patent Nos. 4,329,384 ~Ve~ley et al.)~
4,330,590 (Vo~ley~; and 4,379,201 (Ye~ley), all of which are incorporated herein by reference, are al~o preferred crosallnking agent~ or composition0 or ~pplication~ which reguire no further melt proce0~ing or solvent ca~t~ng.
Sllane~ can al~o bo used a~ croBBlinkers. Sultabl~ ~Llane~
Lnclud~ trialkoxy ~il2nes having mono-ethylenically unsaturated functionality. Other ~uitable silane~ includ~ ~ilanes hav~ng dialkoxy or monoalkoxy ~ubstituted ~ilan~ groups having mono- -ethylenically un~aturated fun~tionality.
Compositions of the invention which require further ;~
proce~aing and undergo cro~lin~in~ by expo~ure to ul~raviole~
35 radiation following the inltial polymeri~ation may employ ~everal ~`
preferred clasae~ of'cro~slLn~er~ including~
; chromophore-~ubstituted halomethyl ~-txiazines, such a~ tho~e in the Yesley Patent~ de~cribed above, ~11 of wh~ch are incorpcrated herein by reference; mono-ethylenically un~aturated aromatic ketone~, particularly 4~acryloyl-oxy-benzophenone, a~ de~cribed by Xell~n et al. in U.S patent ~o. 4,737,559, which is ~ncorporated herein by r~f~r~nc~.
The pr~eure Ben~it~e adh~iv~ o~ thi~ inv~ntivn ~hculd compxlae from about 10 to about 50 ~ by weight of at least one W~ 131~7 .~ $ ~ /US~2/1(~776 llnear or branched alkyl acrylate or methacrylate having from 12 to 26 carbon atoms; from about 50 to about 90 ~ by weight of at lea~t one linear lower alkyl acrylate (C4-C~ or branched lower alkyl acrylate ~C4-cl2); and 0ufflcient cro~nl~nker to impart S cohe~ive strength to the a~he3ive. More preferably, the novel and unobYious pre~sure sen~ltiva adhesive should comprlse from about 30 to 50~ by weight higher linear or branched alkyl acrylate or -~
methacrylate e~ters having alkyl groups from 12 to 26 carbon atome; from about 50 to about 70~ by weLght lLnear or branched lower acrylate or methacrylste having al~yl group~ from about 4 to 12 carbon atoms and from about 0.05 to l.O~ and pref~rably, from about O.l to about 0.5~ by weight cro~alink~r. The adhe~i~e should have enough tack to adhere to a contact ~urface and have ' ~-aufflcLent peel adhesion to allow a ~ub0trate coated with the lS adhe~Lve to be easily removed from a contact surface.
The photoproce~ ble adheEi~ve~ can be polymerlzed using any ~olution polymerlzation method. ~n the preferred method, the monomers along with the solvent and cros~linker are charged into a four-neck reaction ve~el which is equipped with a ~tirrer, a 20 thermometer, a condenser, addition funnel an-~ a th~mowatch. ;~
After the monomer 1~ charged into the reactlon ve~0el, a concentrated thermal initiator uolution i~ added to the addition funnel. The whole reaction veasel and addit:Lon funnel with their content~ are then purged with nitrogen to create an inert 25 atmosphere. Once purged; the eolution within the vee~el i~ heated -~
to about 55 C and the initiator i~ added. A 98 t~ 99% percent conver~ion ehould be obtained after about 20 hours.
If the ~olution i0 then coat~d onto a 0ub~trate and no further proce3aing i~ deaired, the coating can be cured by exposure to ultraviolet light.
I the solut~on 1~ not caet, but in~tead a hot melt coating ~ -i~ da~ired, the ~olven~ is ~trip~ed. The ~olYent l~ stripped by apply~ng the mixture onto a ~iliconized relea~e liner which is 'chen he~tsd re~ulting in ~olve~ #vaporatlon. Thus, an adhe~ve 35 product i~ left ~n solid form. The adhesive 1~ then heated from ~-~
about 145 C to abo~lt 170 C to reduce melt vl~cos1ty, coated onto a suit~ble sub~trate ~nd then cured by ~xpo~ure to an ultraviol~t - ;~
light source.
Anoth~r method of apply~ng the adhesive of the pre ent ~-in~ention compxis~ W prepolymerization of the mono~er mi.xture to a ~yrup~ e con~tency, followed by the additlon of a cro~linker. A suitable cros~llnker i~ th~n added to a ~yrup-like mixture. Next, thi~ ~yrup~ e mixture i~ knle-coated onto a ~,' - `,'', ....

, .

2 ~2 6 ~3~ ~ 8 - P~US)2~1077b ~ub~trate and UV polymerized in an lnert atmosphere to yield the Pinlsh~d adheslve coatlng.
The adhe~ive of the present lnvention can also be polymerlzed by char~ing the monomera wlth ~olvent, ~nit~ator and a ~ilane croaslinker lnto a three-neck reactlon ve~el equ~pped with a ~tirrer, a thermometer, a thermowatch and condenser. ~fter the mOnOm8r i8 charged into the reaction ves~el,-the whole reaction veasel with lt~ contents i8 purged with nitrogen and heated to 55 C. Aft~r about 20 hour~, a 97 to 98~ percent conversion should be obtained. ~he material ~ then coated on a ~ub~trate and dried in an oven. Typically, a catalyat can be added to the ~olution prior to coating and oven drying. In the presence of moisture, a cros~linked adhesive i~ obtained and no further processing is required.
Tho removable PSA of the present ~nvention depending upon lts vl~co~lty, can be coated via any of a variety of conventional coatln~ method~, Duch ~ roll coatlng, knlfe coatlng, hot melt coating, or extru~ion. The composition can be applied to at least a portion of at lea~t one ~urface of suitable flexihle or lnflexible backing or ~heet and cured to produce PSA-coated flheet materials. For example, it can be placed on a backing to form a tap0. Or it can be applied to a ~heet to form pre~ure sen~itive ~heets. For many purposes, it is preferred that the adhesive can be coated on both ~ides o~ a sheet. Tho~e skllled in the art will recognize that novel adhesiYe can be applied to a variety of cheet~ and backings and can be ~imultaneou~ly coated on both ~ide~
of the ~heet or backing. U~eful flexible backlng materlal~ ~-include paper, plastic films ~uch aa poly~propylene)~
poly~sthylene), poly(vinyl chloride), poly(tetrafluoroethylene), 30 polyester te.g., polytethylenel terephthalate)3~ polyimide film -~
~uch a3 DuPont'~ ~apton~, cellulose acetate and ethyl cellulose.
~acking~ can al~o be of woven fabric ormed of threads of synthetic or natural materiala ~uch ~ cotton, nylon, rayon, gl~, or ceramic material, or they can be of nonwoven fabric such ~ ;
a~ air-laid web~ of natural or aynthetic fibers ox blend~ of these. In addition, ~uitable bac~inga can be formed of metal, metallized polym2ric film or ceramic sheet material. PSA-coated sheet material3 can take the form of any arti~le conventionally known to be utiliæed with PSA compo~itions, ~uch a~ label~, tapes, tran~er tape~ ~compri~ing a film of the PSA borne on at lea~t one relea~e l~ner), ~igns, covers, marking indiGes, and the like.
Prlmers can b~ util~ed, but they are not alwaya nece~ary. ~-W ~ 4~ q7 PCT/US~2/10776 9 2 1 ~ Y ~
Te~t Method~
~emovability Adhesive~ of the present Lnventlon are con~idered removable if they are removed cleanly from a te~t sub~trate without causing S any dam~ge to the te~t sub~trate over a r~nge of peel rate~ and varied perlod~ of dwsll at room temperature.
A atrip 0.127 dm in width of the ~heet coated with the adheslve to be tested Ln applied to the horlzontal surface of a polye~ter, treated polye~ter or paper test ~ubstrate with at lea~t 1.27 llneal dm ln flrm contact. Three pas~es ln each dlrection with ~ 2 kg hard rubber roller are us~d to apply th~ ~trip. If ~-~
air bubble~ are entrapped between the test eubstrate and the te~t strip, the ~ample ~ di~carded. After on~ day or one week dwell, ~ ~ -th~ free end of the coated atrip i~ doubled back nearly touching 15 lt~elf 80 the angle of removal will be about 135. The free snd i~ then pulled by hand at a varLety of peel rates. The removablllty and peel force are ~udged according to the following ratLng~ and recorded:
qood - ~ample~ that are removed from the te~t sub~trate ~0 without damaging or leaving re~ldue on the te~t substrate and wh~ch alao exhLbit hLgh peel forc~ and yet does not damage the paper backlng ovex a range o~ peel rate~;
anare~ve - ~ample~ that are removed from the test ~ubstrate without damag~ng or leaving residue on the te~t ~ub~trate, but which can only be removed from thP te~t ~ubstrate at a ~low peel rate without damaging the paper -backin~
ras~v - sample~ that are removed from the test ~ub~trate -~
without d~maging or leaving residue on the te~t ~ub~trate, but which are too sti~f to be removed ~moothly; ~ ;
tear - sample0 that di~play too high a peel adhesion to the ~ ~
test ~ub3trate, causing te~t ~ubstrate and/or paper backing - -to tear or del~mlnate at ~ny pael ratet ~ho~t - ~amplee that l~ava a ~ry th~n, non-tacky ~dheslve re~idue on ~he test ~ub~trate when removed from the ~ ~ .
polye~tar and treated polye~ter samples; and ~ ;
weak - ~ample~ that ha~e low tack and low peel.
cobe~ive fallure - uamples that leave adhe~1ve residue on both the paper backins and the test ~ubstrate.
Pael Adhe810n .
Peel adhe~on 18 the forca raguired to remove a aoated flexlbla ~heet material from a test ~ub~trat- mea~ured at a ~
spacific angle and rate of removal. In the sxample~, thi~ force ;~
'".'~' ' ,' "~., ', .
-W~ 5~C~'/ US~2/ 1 0776 ~? ~ ~, ~ 9 ~ 0 1~ expre~ed ln Newton~ per declmeter (dm) wldth of coated aheet.
The procedure f ol lowed i~:
A ~trlp 0.12~ dm in width of the ~heet costed wLth the adhee~ve to be teated ~a applLed to the horlzontal aurface of a polyeater, treated polyaster or paper test sub~trate with at lea~t 1.27 lineal dm in firm contact. Three passes in each direction wlth a 2 k~ hard rubbar roller are u~ed to apply the strip. If air bubbles are entrappad between the te~t ~ubutrate and the te~t 0trip, the aample 1~ di~carded. The ~ree end of the coated strip la doubled bac~ nearly touching itsel 80 the angle of removal will be 180. The free end is attached to an adhe~ion teeter ~cale. The polyester or paper ts~t ~ubstrate i~ clamped in the ~aws of a tennlle te~ting machine which 1~ cap~ble of moving the ~ubntrate away ~rom the ~cale at a constant rate of 2.3 maters per mlnute. ~he dwell tlme after roll down l~ 30 s~conds. The scale read~ng ln Newton~ 1~ recorded a~ the tape i~ paeled from the gla~ ~urface.

~bbreviation~ and Traden~mes AA acrylic acid AB~ - 4-acryloyl-oxybenzophenone 8A - n-butyl acrylate ECA - eicoaanyl acrylate HCA - bexaco~snyl acrylate ~DDA - 1,6-hexanedlol diacrylate IOA - i~ooctyl ~crylate I~DA - ~sotridecyl acrylate -~
LA - lauryl acrylate ~MA - laur~l methacrylate -~
30 ODA - octade~:yl acrylate ~
O~cM - n-octyl acrylate ODMA - octadecyl methacrylate SIL - methacryloxypropyltrLmethoxy~ilane ~old under trade name Silane A-174 by Union Carbide ~ -YAZO~ 64 - 2,2'-azob~(isobutyronitrile), available from DuPont Th~ percentagea in thia speciication and appended claims are all percenta9a~ by weight unle~ oth~rwi~e not~d.

~L
In 8 500 ml our-neckQd reactlon ve~aelr eslulpped with a ~tlrrer, th~rrnomet~r, condlenser, addltlon funnel and thsrmowatch, 84~0 gram~ of IOA, 75 grams of O~A ~Q 48~ ~olids in ~:
ethyl acetate), 121 gramB of ethyl acetate, and 0.92 grarn of A8P
(~j 2Ç~ sollde in ethyl acetate) w~re charged. A solution s:~f 0. 36 ";,''"'."''''' W ~ 147 21 2 61~ ~ 2 PC'r/US~2/1(1776 -- 11 -- , , , gr~m VAZO- 64 ln 20 yr~ms of ~thyl acetat~ wAn added to tha addltion funnel. soth the eolutlon in the reaction ve~al and the mater~al~ ln the addition funnel were then purged with argon ~or nitrogen)~ The ~olution in the reaction ve~sel was then heated to S 55C and inltlator wa~ added. After about 20 hours, a 98-99 conver~ion wa~ obtained. The mixture wa~ then coated from ~olution onto light weLght, unprimed paper. No bleeding of the adhe~ive ~olutlon through the paper was ob~erved. An o~en dried coating thicknen~ of 0.5 to l.O mil of the adhesive ~olution wa~
obtained. The coating was pas~ed three times under W light lPPG
W proce~or equipped with medium pre~sure mercury 1amPB at 30 Watt~/2.5 cm) at 25 m~ter~/min.
The coated paper was then adhered, a~ ~pecified in the above removability te~t, to two different te~t sub~trate~: one being an lS lOO mm thick untreated poly~ethylene terephthalate~ eheet ~PET~', commercially available a~ PP2410 from Minne~ota Mining and Hanufacturing Company~ the second being a lOO mm thick sheet of poly~ethylene tereph~halate) film ~urface treated with hydrolyzed cellulose acetate ~"treated PETn, commercially available as G3120 20 from ~innesota Mining and Manufacturing Com1~any). Removability ;~
was then maa~ured for sample~ from both te~1: substrate~ after dwell of one day and one week.
The te~t re~ults were reported in TabLe l. -Table l ~OVABILITY
~ _ ~ ~ ~.
Com- Wt. % PETtreated PET
po~ition ratio 1 day 1 week 1 day l-week ' , . ~ _ ,_ _ __. ' '-IOAJODA~ 70/30J good good good good 30 ABP 0.~
_ ~ =, ~ __ _= __, _=
' ' ' Comparative_~xam~le~ C-l~ C-2 and C-3 Ex~mple~ C-l, C-~ And C~3 were prepared a~eording to the -~
~rocedure of Example l. However, the example~ were not prepared with a l~near or branched higher alkyl acrylate or methacryla~e.
The removabilities of th2~e compo~i~lons are reported in Table 2.

' . ' :'`
,~ ,:..

' ~ ~' ''''' ' `-; ', . " :' ~ ,.',,.

W ~131~7 ~ PCrtUS92/10776 ~,~?,6~ 12 -Table 2 REM~VA~ILITY
~ = _ _ -Ex. Com- ~t. ~ PET treated PET
po~i- ratio = ~ ¦
tion l day l week l day l week _ _ . _ _ I
C-l /0AA/OA 70/30/ aggre~s aggre~s a~gress aggra~ ¦
l . I . -5 1 C-2 IOA/OA 70/30/ ra~py tear tear tear ¦ :
cM/ABP 0.2 ~ ~ --_ I
IO /3A 70/30/ aggre-~ ~ggr~-- aggr~n~ ¦

The example~ illu~trate the need for the inclusion of at least one llnear or branched higher alkyl acrylate or methacrylate in the romovable adhe~ive compo~ition of the pre~ent invention.

Example~ 2-S
Examplns 2-5 were pr~pared according to the procedure outll~ed in Example l. Their removabllities are recorded in Table 15 3.
Table 3 REMOVABILITY
_ . _ Ex. Com- W~. ~ PET ~ treated PET
position ratio _ . _ ~=~====
l day l week l day l we~k ¦
___ _ _ __ __ _ _ :

2 ABP 90/l0/ good good good good ~
I __ _ . _. _ .. . I ,. .:~
20 3 ABP o22/ 9QQ~ good good good : .
l ~. . -_ _ I ' ~ ' 4 IOA/O~A/ 60/40/ good good good good I ; ~
A8P 0.2 : ~ I . .
. . _ ~.~ _ . . I . ., IOA/ODA/ 50~501 good good , good~ good . . .
A~P 0.2 ~
~ _ _ ,_ _ _ __ ~ _ _=
Exampl~s 2-5 illuEtrate the com~o~tional range at which ` -~
25 IOA/OD~ adh~ive~ retain their removabllity ~rom both test , -~.
~ub~trate~.

', ....

W ~ l47 21 ~ 6 ~ ~ 2 pr/us92/lo77G

~m~_atlve Example~ C-4 ~D C-5 Comparat~ve Example~ C-4 and C-5 were prepared ~n accordance with Example 1. The~e two comparatlve example~ were prepared with hlgher alkyl acrylate compo~ltlon~ ln exce~ of the ranges of the adheaive of the present inYention.
Table 4 REMOVABILITY
_ _ - . ' Ex. com- wt. % PET treated PET
po~ition ratlo - _ . -1 day 1 wee~ 1 day 1 week ¦
__ _ ___~ _ I
C-4 IOA/ODA~ 400/60/ tear tear tear tear I ~.
~ . . 1 ,.~:.
~ IOA/LA/ L ~ 2 we k weak weak wea~

~ ':
Aa can be ~een, Comparative ~xamples C-4 had too much adhe~ion causing substrate tear and C-5 exhibited virtually no ' .
adhesion. ~ ~ :
~
ExamDle~ 6-15 --. .
Example~ 6-15 were prepared ln accordance with the procedure o~ ~xample 1. Howevsr, different higher al,kyl acrylate~ and methacrylate~ were used. The re~ultB of the test~ are reported in : :
Table S.
~ ~ , ' ~'.'-'';' ' ""

~ !

' "''~""

.~. :",`'.
~" ~ ' ~""'' ~""'~"',', '' .',, ',' "'i : ~`.' ' . ' ~

W ~J~ 7 r~T/US~tlO776 Table 5 ~EHOV~BI~ITY
__ _. ,_ ~ ~_ Ex. Com Wt. ~ PET traated PET
position ratio _ _ _ -1 day 1 week 1 day 1 wee~ ¦
~ _... _ 6 IOA¦LMA/ 90/10/ good good good good l ~ _ _ . 11 5 17 IOA/LMA/ o0,/20/ ~ good good good ~ ~
~- ~ _ _ l ¦ ~ IOA/LMA/ 50/50/ good good good good ~ ABP 0.2 _ . _ ¦9IOA/ODM~/ 9021~ good goodgood qood I- _ ~ _ .-¦ 10 IOA/ODMA/ 70/30/ good good good good A3P 0.2 --_ __ _ ___ _ _ ¦ 11 IOA/ODMAt 90210/ good good good good I__ . __ __ __ _ __ 12 IOA/ITDA/ 0/3/ good qood good good _ . ~ _ _ _ _ _ _ 13 ABP 70/30/ good good good good ¦
,, _ ~ _ _ . _ 14 IOA/HCA/ 70/30/ good .~ood good good l_ ~_ _ . . _ _.
~ IOA/~A/ 60/40/ good ~ good good ~:

~x~mple~ 6-15 lllu~trate that compo~itional range ~arying ~: :
higher alkyl acrylates and methacrylate~ at which he adhe~ives retaln the~r removability from both te~t eu~Btrate~.
~ ;:
~amDlas 16-20 ~ -~
Example~ 16-20 were prepared in accordance with the procedure of Examplq 1. How~ex, butyl acrylate wa~ u~ed ln~tead of l~ooctyl ~crylate~ In addltlon, a number of dlfferent welght ratio~ of butyl acrylate were u~ed. ~e8t re~ult~ are 8hown in , :~:
Ta~le 6. :~
. .

~, ~V~ 9~ 7 2 1 2 6 9 X 2 Pcr/us~ 0776 ~ 15 -Tahle 6 :
~EMOV~BILITY
_ v_ ~ 1 Ex. Com Wt. ~ PET 1 treated PET
po~itionrat io ~G===~ _ _ day l week l day l wee~
I _ _ . ~ _ . ', :, 16A/ODA/900/l0/ good good good good ~ .
I- , _ I ~' l78A/ODA/ 80/20/ gge~ C good good ;~

l8BA/ODA/0./3/ good good good ~ood . . . _ _ l9BA/ODA/60/40/ good ~oodgood good _ _ _ . ..
20 AA~/ODA/ _ 0.2 good goodgood _ :;:

, Example~ 16-20 illu~trate that ~ompoE1itlonal range of butyl acry~teE3 at whlch the adheE~l~e~ retain their removability from both test e~bHtrates. :: .
~ and C-8 Compar~ti~e Example~ C~7 and C-8 wer~ made in a~cordanre wlth the procedure of ~xample 16. The~e two comparative example~
were prepaxed with hi~her alkyl acrylate ~omposltion~ in exce~s of the rang~s o~ the adhe~ ve of the pr~3ent invention . T~t result~
are reported in Table 7.
Tabl~ 7 ~HOVABILITY
_ _ ~ ~: ,, :.. "~,.
~xO ~om- Wt.-~ PET ~ treated~PE~
po0i- ratio _ = . _ I ~ `: .
tio~` ~ l day ~l wee~; l day :l week __ _ _ ~ _ ~ , .,.,:~
C-6 BA/ODA 40/60/ 1 ~hocky: tea~ tear tear ~
/ABP 0. 2 : : ~ ::
__ _~ _____ _ '''""~ '' C-7 BA/ DA 30/70/ ¦ weak weak weak weak ~ .
_ _ . - . ~= __ . = .
A 3 can be ~ean, C ,mp rati~ Examples C-6 had too much adhealo~ and -7 exhibited virtually no adhe~ion at all. ~

: ,. . .:
. ,- .. ., ,;.
`- ' ,.'~', W ~ 47 2 i.æ ~ ' PC~ 92/1n776 Exampl~ 21 ~ hle example demon~trates the preparation and removabllity of a hot melt proce~ible adhe~ive of thi~ invention.
In a 500 ml four-necked r~actlon ve~sel, equlpped with a ~tirrer, thermometer, condensor ~nd thermowatch, 84.0 grams of IOA, 75 ~ram~ of ODA (@ 48~ solida ln ethyl acetate)~ 121 grams of athyl acetate, and 0.92 gram of ABP (@ 26~ ~olids in ethyl acetate), and solution of 0.36 gram V~ZO~ 64 ln 20 grams of ethyl acetate wera charged. ~he ~olutlon ln the reactlon ves~el wa3 then pu~ged with nitro~en to create an inert atmosphere. The eolutlon in the reaction vessel wa~ then heated to 55c for 20 hour~. A 98-99~ conv~r~ion was obtained. Tha mixture was then ; -~
coated from solution onto a siliconized releasa lLn~r ~nd oven dried at 65C for 15 minutes. The solid polymer was then removed from the liner and placed into a small piston coater. The solid polymer was then hea~ed to 145-170C ~nd coated onto a roll of 30 pound mschlne-glazed bond paper ~tock. The coating was pa~sed three times under W llght tPPG UV processor e~uipped with medium pressure mercury lamp~ at 30 Watts/2.5 cm) at 25 metars/min.
coating thickne~ of 0.4 to 1.0 mil of the hot melt adheQlve was obtalned. -~
~ he coated paper wa~ then adhered, as ~pecified in the aboveremovability test, to two different te~t ~ub~trates: one b~ing an ~00 mm thick untreated poly~ethylene terephthalate) ~heet (~PE~", ~ommercially available aa PP2410 rom Minnesota Mining and ~anufacturing Company) the ~econd being a 100 mm thick ~heet of poly(ethylene terephthalate) film ~urface treated with hydrolyzed cellulo~e acetate ~treated PETn, commercially avaiIable a~ G3120 from Minne~ota Mining and Manufacturing Company). Removability was then measured for sample~ from both test sub~trate~ after dwell of one day and one week~
Table 8 REMOVABILITY -~
~ _~_ . . - _ '~
Ex. Com- Wt. % PET treated PET ~;
pos~- ratio _ - _ _ _ tion 1 day 1 week 1 day 1 w~ek -~
~ _ __ __ ._ _........................................................ : '' ''~.
3~ ~ IOA/ ~ 70t30/ good gc~d good 9~ ~
~.:~.~'.''.'' ' Examples 22-2~ were ~sde in aocordance wlth Example 21.
Compo~it~ons and welght ratio~ of ~he compo~itlon~ are r~ported in Tabl~ 9.
~ ~ .

,~" .: :.
-.:..

W~ ~tl~l~l7 P~/US~2/1077fi - ~7 ~ 2~2~
T~bla 9 ~E~OVABI~ITY
_ _ _ _ _ Ex. Com- Wt. ~ PET treated PET
poai- ratio -I . tion 1 day l week 1 day 1 week 22 IOAA/ODA go2lo/ goodgood good good ¦ .
I I
5 23 /OAAJODA ~0¦20/ qoodgood good good ¦ .-_ _ _ _ 24 IOA/ODA 60240/ aoodgood tear good ¦
I _ I
2S BBA/ODA/ o23~ aood good good good l _ . _ _ _ _ _ 26 8A/ODA/ 0~/4/ good ~ood good good ~ _ _ _ _ ': :' ~ PA/ODA/ 0.2 qccd goo~ good goo~

~, ~ aan be ~een, Example~ 20-25 all exh1bited good :. removabillty.
Exam~le~ 28-31 Examples 28-31 were prepared in accordance with the 15 procedurs of Example 21 with ~arying compositionB and weight :---ranges~ Example~ 28-31 were teated for peel adhes~on on a variety of aubatrates. Three different te~t ~ubstrates were used: one being a 100 mm thick untreated poly~ethylene terephthalate) sheet ~- :
(nP~Tn), he Eecond being a lOO mm thick sheet of poly(~thylene O terephthalate~ film ~urface treated with hydrolyzed cellulo~e ~-ac2tat~ ("treated PET~) and the third being copy paperO P~el :
adhesion wa~ then measured for ~mple3 ~or all thraa test sub~trates. The tQ8t re~ultH ara ~hown in Table lO.
,.
25 1 :
, .. .

, ~

W~ 7 PCr/US~Z/1077b ~, 6 9 ~ 18 Peel Adheeion IN/dm) _ _ Ex.compoa~tionwt. ~ PET PET PAPER ¦ . -T:~EATED ~
_ 28IOA/ODA/ABP60/40/0.2 1.8 0.7 1.3 I _ . . _ _ _ , 2~BA/ODA/A~P70/30/0.2 9.2 9.2 10.5 I_ . . _ _ ~ .
30BA/0DA/ABP60/40/0.2 15.1 13.6 25.8 ~ _ 31BA/ODA/AsP50/50/0.2 7.4 8.3 6.8 ¦ :
l _ A~ can be seen, Examples 28-31 exhibited suitable peel t 10 ,adheflion .

Example 32 wa~ prepared in the aame manner a~ Ex~mple~ 28-31. However, two higher alkyl acrylatea were used ine~ead of one.
The te~t re~ults are shown in Table 11.

= ; . _ _ _ -- 1 :: ' Ex. Com- Wt. ~ P~T ¦ treated PET l ::.
poaition ratio _ ~ - ~ .
1 day 1 week 1 day 1 week ::
. , . . _ ~ - .. .:
32 IOA/ODA/ ~0/20/ good good good good LMA/ARP 10l0.2 . _ _ :-- ~ _ .................... _ ~ . I ., A~ can ~e eoen, Exampie ~ exhlbltea gooa --removability.

EXAMPL~S 33-34 ~-~xample~ 33-34 w~r~ prepared in same manner ae Example 1.
~owever, the ratio~ of the cros~link~r ABP were varied. Teet re~ult~ are recorded in Table 12.
`,..'. ' .
. ~,.
'"' ' ~'"''':"
;~ ';'' ~
'~ '' " ~, . .
' ."'',~, . ' ,: ' ! . : . . ' `' ~' ~''' " ' W~ 17 212 6 ~9 ~ ~ P(~/VS~2/11)776 = ==
EX. COMPOSI- WT. ~ RATIO PEEL ADHE~ION
TION ___~_~ _ _ _ PET TREATED PAPER
_ _ ~ ..
IOBA/ODA/ 70/30/0.3 6 6 3.1 1.5 ~ IOA/ODA/ 70~30/0.40 7 1.3 0.7 ¦ .

COMPARATIVE EX~MPLE 8-C
Comparat~ve Example 8-C was made in the same mann~r a~
~xample 1 wlthout any crossllnker. The re~ult~ are reported in Table 13. -TABLE 13 : -_ ., ._ _ _==,, _ _- , Ex. COMPOSI- WT. ~PEEL ADHESION ¦ ..
TION RATIO _ _ PET PERETATEl~ PAPER ¦ ~ :
_. _ __ I
8-C ABP 70/30/0COHESIVE FAILUF ¦

~XAMPLES 35-38 .~- , Example 35 wa~ prepared in the following manner~
O.1 gram of 2,2-dimethoxy-2-phenyl acetophenone sold under the tradename Eacacure ~Bl by Sartomer Company wa~ dissolved in 100 gr2m8 of a 70~30 monomer mixtuxe of i~ooctyl acrylate and octadecylacrylate. The mixture wae pur~ed with nitrogen and prepolymer~gd undex a ~et of 40 Watt fluore~cent W light~
re~ult~ng in a mixture having syrup-like con~i~tency. Next, 0.18 gramB of ~DDA were adde.d~ogether with 0.1 gram~ of E~cacuxe RB1 to th~ syrup-like mixture. ~ ~:
~ Th~ m~ture waA then ~nlfe-coated onto a ~ubstrate a~d compl~tely polymerized under a bank o~f fluore0cent W light~ in an .
lnert atmosphere. Three:d~fferent te~t sùbstrat~ were used: one being a lOQ mm thick untreated poly(ethylene:terephthalate) sheet (nPE$n)~ the ~econd being a lOO mm thick~:~heet of poly~ethyIene 30 terQphthalate~ fllm ~urface trzated with hydrolyzed celluloee ~ :
acetate ~"treated PET") and th~ third being:copy paper. Peel ~iV~ 3~ l7 ~ )X9~/ 1 077() 'J~ 20-adhe~lon wa0 th~n m~a~ured f or samplea for all thr~e test ~ub~trate~
Exampls~ 36-38 were prepared in the ~ame manner a~ Example 35 except that the ~mount of HD~ and/or ODA was changed.
The compo~itiona and weight ratio~ of Examples 34-37 ar~
reported ~n Table 14 as are the re~ulta of the testing.

_ _ . ~
EX~ COMPOSITION WT. ~ RATIO PEEL ADHESION
._ . _ _ _ PET TREATED PAP~R
_ ............... _ . _ .
IOA/ODA/HDDA 70~30/0.1 ~2.5 30.4 48.4 t ' ' 10 3S IOA/ODA/~DDA 70/30/0.~ 17.5 20.4 24. 7 ~.
_ ~ I , 37 IOA/ODA/HDDA 80/20/0.1 34.8 31.7 5~.1 _ . _ _ . . _ . I
3~ IOA/ODA/HD~A 80/2010.2 20.6 24.3 30.2 I _ . _ __ _. :'.
EXAMPI.E5 39-41 .
15 Example 39 wa~ prepared in the following manner: A 500 ml. three-necked reactlon ves~el, equlpped with a 0tirrex, thermometer, thermowatch and condensor was charged with 84 grams of IOA, 75 gram~ of ODA ~@48 ~ ~olid~ ~n ethyl acetate)~
121 gram~ of ethyl a~etate and 0.2 gr~me of ~llane cro~slink~r 20 ~old under the tradename Silane A-174 by Union Carbide. Next, a ~- .
~olution of 0.36 gram~ of VAZO~ dis~olved in 20 gram~ of ethyl acetate wa~ added to the charge. Then the ves~el wa~ purged with:-~
nitrogen and heated to 55C for about 20 hour~
Prior to ooating, about 0.04 gram~ of dibutyl tin dilaurate -~ ~
~5 catalyBt was mixed into the ~olution. The material was coated onto .:
the sub~trate and dried in the oven. Three different test sub~trates were used: one bein~ a 100 ~m thick untreated polytethylene ter~phthalate) sheet (rPET~ ~r th~ ~econd ~lng a 100 : :~
mm thicX ~heet of poly~ethylene terephthalate) film eur~ace 30 treated w~th hydrolyzed cellulo~e acetate ("tr6ated PE$") and the : ~
third bein~ copy paper. Peel adhe~ion wa~ then mea~ur~ on all. .b three test substratQ~
Example~ 40 and 41 were made in the ~ame ~anner except the amount of S~L was ~arl~d as indicated in Table 15. The results of 35 the est~ng are reported in Table 15. ~
.,.. ~.:, ,.. .....

~ ~.' '' W ~ 7 PCr/~'S~2/1~776 - 21 ~ 1 2 6 ~A8LE 1 5 Co~POSITION WT. ~ RATIo PEEL ADHESION (N/dm _ ~ ,.
_ PET ~E~ ED PAPER

39 ~OA/ODA/SIL 70/30/0.2 2.4 3.5 5.3 l _ . __ . , _ I
I~A/ODA/SIL 70/30/0.3 l.8 l.8 l.8 I _ _ _ S 41 IOA/ODA/SIL 70/30/0.4 l.~ l.5 l.6 L _ . _ _ _ _ _ :~, In summary, a novel and unobvious adhe~ive ha~ been de~cribed having a low melt visco~ty. Althou~h specific embodiment~ and examples of the present invention h~ve been de~crib~d herein, it should be borne in mind that these are by way oE explanation and illu~tration and the present invention is not limited thereby. Certainly modifications which are within the ordinary skill in the art are considered to lie within the scope of thia ~nventiorl aB defined by the following claim~ including all :~ .
equlvalent~.

Claims

We Claim;

1. An acrylic pressure-sensitive adhesive comprising:
a) from about 10 to about 50 % by weight of at least one higher alkyl acrylate having an alkyl group from 12 to 26 carbon atoms;
b) from about 50 to about 90 % by weight of at least one lower alkyl acrylate having an alkyl group from 4 to 12 atoms wherein said alkyl groups of said lower and higher alkyl acrylates do not simultaneously have 12 carbon atoms; and c) sufficient crosslinker to substantially prevent adhesive transfer, wherein said adhesive composition has high peel strength while maintaining good removability.

2. The adhesive of Claim 1 wherein said alkyl group of said lower alkyl acrylate is linear and has 4 to 8 carbon atoms.

3. The adhesive of Claim 1 wherein said alkyl group of said higher alkyl acrylate has from 13 to 26 carbon atoms.

4. The adhesive of Claim 1 wherein said crosslinker is selected from the group consisting of a multifunctional acrylates, multifunctional methacrylates, chromophore-substituted halomethyl-s-triazines, benzophenones, acetophenones, silanes and mono-ethylenically unsaturated aromatic ketones.

5. The adhesive of Claim 1 wherein said crosslinker comprises from about 0.05 to about 1.0 % by weight of said adhesive.

6. The adhesive of Claim 1 wherein said adhesive comprises from about 30 to 50 percent by weight of said higher alkyl acrylate; from about 50 to 70% by weight of said lower alkyl acrylate and from about 0.1 to about 0.5 % by weight of said crosslinker.

7. An adhesive coated sheet material having a bearing on at least one major surface thereof an adhesive composition comprising:
a) from about 10 to about 50 % by weight of at least one higher alkyl acrylate having an alkyl group from 12 to 26 carbon atoms;

b) from about 50 to about 90 % by weight of a lower alkyl acrylate having an alkyl group from 4 to 12 atoms wherein said alkyl groups of said lower and higher alkyl acrylates do not simultaneously have 12 carbon atoms; and c) sufficient crosslinker to substantially prevent adhesive transfer, wherein said adhesive composition has high peel strength while maintaining good removability.

8. The sheet of Claim 7 wherein said adhesive comprises from about 30 to 50 percent by weight of said higher alkyl acrylate; from about 50 to 70% by weight of said lower alkyl acrylate and from about 0.05 to about 1.0 % by weight of said crosslinker.

9. The sheet of Claim a wherein said crosslinker comprises from about 0.1 to about 0.5 by weight of said adhesive.

10. The sheet of Claim 7 wherein said alkyl group of said higher alkyl acrylate has from 13 to 26 carbon atoms.

11. The sheet of Claim 7 wherein said crosslinker is selected from the group consisting of a multifunctional acrylates, multifunctional methacrylates, benzophenones, acetophenones, chromophore-substituted halomethyl-s-triazines, silanes and mono-ethylenically unsaturated aromatic ketones.

12. A method of making a pressure-sensitive adhesive coating sheet material comprising the following steps:
a. polymerizing an adhesive mixture comprising a) from about 10 to about 50 % by weight of at least one higher alkyl acrylate having an alkyl group from 12 to 26 carbon atoms; b) from about to to about 90 % by weight of at least one lower alkyl acrylate having an alkyl group from 4 to 12 atoms wherein said alkyl groups of said lower and higher alkyl acrylates do not simultaneously have 12 carbon atoms; and c) sufficient crosslinker to substantially prevent adhesive transfer, wherein said adhesive has high peel strength while maintaining good removability;
b. coating and drying said adhesive onto said sheet; and c. curing said adhesive by exposing said adhesive to ultraviolet light.

13. The method of Claim 12 further including the steps of:
a. solidifying said polymerizable adhesive;
b. heating and coating said adhesive prior to curing said adhesive on said sheet.

14. The method of Claim 12 wherein said adhesive comprises from about 30 to 50 percent by weight of said higher alkyl acrylates; from about 50 to 70% by weight of said lower alkyl acrylate and from about 0.1 to about 0.5 % by weight of said crosslinker.

15. The method of Claim 13 wherein said adhesive comprises from about 30 to 50 percent by weight of said higher alkyl acrylate; from about 50 to 70% by weight of said lower alkyl acrylate and from about 0.1 to about 0.5 % by weight of said crosslinker.

16. The method of Claim 14 wherein said crosslinker is selected from the group consisting of selected from the group consisting of multifunctional acrylates and methacrylates, benzophenones, acetophenones and chromophore-substituted halomethyl-s-triazines.

17. The method of Claim 15 wherein said crosslinker is selected from the group consisting of selected from the group consisting of chromophore-substituted halomethyl-s-triazines, benzophenones, acetophenones and mono-ethylenically unsaturated aromatic ketones.

18. A method of making a pressure-sensitive adhesive coating sheet material comprising the following steps:
a. UV prepolymerizing an adhesive mixture to a syrup-like consistency wherein said mixture comprises: a) from about 10 to about 50 % by weight of at least one higher alkyl acrylate having an alkyl group from 12 to 26 carbon atoms; b) from about 50 to about 90 % by weight of at least one lower alkyl acrylate having an alkyl group from 4 to 12 atoms wherein said alkyl groups of said lower and higher alkyl acrylates do not simultaneously have 12 carbon atoms;
b. adding crosslinker to said mixture;

b) from about 50 to about 90 % by weight of a lower alkyl acrylate having an alkyl group from 4 to 12 atoms wherein said alkyl groups of said lower and higher alkyl acrylates do not simultaneously have 12 carbon atoms; and c) sufficient crosslinker to substantially prevent adhesive transfer, wherein said adhesive composition has high peel strength while maintaining good removability.

8. The sheet of Claim 7 wherein said adhesive comprises from about 30 to 50 percent by weight of said higher alkyl acrylate; from about 50 to 70% by weight of said lower alkyl acrylate and from about 0.05 to about 1.0 % by weight of said crosslinker.

9. The sheet of Claim 8 wherein said crosslinker comprises from about 0.1 to about 0.5 %
by weight of said adhesive.

10. The sheet of Claim 7 wherein said alkyl group of said higher alkyl acrylate has from 13 to 26 carbon atoms.

11. The sheet of Claim 7 wherein said crosslinker is selected from the group consisting of a multifunctional acrylates, multifunctional methacrylates, benzophenones, acetophenones, chromophore-substituted halomethyl-s-triazines, silanes and mono-ethylenically unsaturated aromatic ketones.

12. A method of making a pressure-sensitive adhesive coating sheet material comprising the following steps:
a. polymerizing an adhesive mixture comprising a) from about 10 to about 50 % by weight of at least one higher alkyl acrylate having an alkyl group from 12 to 26 carbon atoms; b) from about to to about 90 % by weight of at least one lower alkyl acrylate having an alkyl group from 4 to 12 carbon wherein said alkyl groups of said lower and higher alkyl acrylates do not simultaneously have 12 carbon atoms; and c) sufficient crosslinker to substantially prevent adhesive transfer, wherein said adhesive has high peel strength while maintaining good removability;
b. coating and drying said adhesive onto said sheet; and c. coating said mixture with said crosslinker to said sheet; and d. UV polymerizing said mixture.

19. The method of Claim 18 wherein said adhesive comprises from about 30 to 50 percent by weight of said higher alkyl acrylates; from about 50 to 70% by weight of said lower alkyl acrylate and from about 0.1 to about 0.5 % by weight of said crosslinker.

20. A method of making a pressure-sensitive adhesive coating sheet material comprising the following steps:
a. polymerizing an adhesive mixture comprising a) from about 10 to about 50 % by weight of at least one higher alkyl acrylate having an alkyl group from 12 to 26 carbon atoms; b) from about 50 to about 90 % by weight of at least one lower alkyl acrylate having an alkyl group from 4 to 12 atoms wherein said alkyl groups of said lower and higher alkyl acrylates do not simultaneously have 12 carbon atoms; and c) sufficient silane crosslinker to substantially prevent adhesive transfer, wherein said adhesive has high peel strength while maintaining good removability;
b. coating said adhesive onto said sheet; and c. drying said adhesive; and d. curing said adhesive in the presence of moisture.

21. The method of Claim 20 wherein said adhesive comprises from about 30 to 50 percent by weight of said higher alkyl acrylate; from about 50 to 70% by weight of said lower alkyl acrylate and from about 0.1 to about 0.5 % by weight of said crosslinker.