CA2196173A1 - Acrylic syrup curable to a crosslinked viscoelastomeric material - Google Patents

Abstract

Solute polymers in solvent monomers form a coatable syrup that can be cured to a viscoelastomeric material when radiation-sensitive hydrogen abstracting groups in either the polymer or one of the monomers are exposed to ultraviolet radiation. The solute polymers can be formed from the solvent monomers.

Description

WO 96/05249 ~ P C . _I/U.J~_. c,.,v2 ACRYLIC SYRUP CURABLE TO A
~ 5 CROSSLINKED VISCOELASTOMERIC MATI~DT~T.
This application is a C~ ~ ~ ~ P~ ~ of U.S. Serial No. 08/282,058 fled July 29,1994, currently pending.

10 BACKGROUND OF TE~ INVENTION
1. Field of the Invention This invention describes a ~ .,F~ -- ;c material with high shear at ambient and elevated t~ Iultia prepared from a blend of cLI~
11117~11u~ aL~d monomers. A process for making this material is also described.
15 2. BackgroundT..I~..,. ~;,..~
Pressure sensitive adhesives (PSAs) made by IJhU~U~JO~ g an alkyl acrylate and a polar cûlJulJ ~ ' ' ~ monomer are known in the art. See, e.g., U.S. Patent Nos. RE 24,906; 4,181,755; 4,3647972; and 4,243,50û. Acrylic-based PSAs exhibit good adherence to high energy Q.e., polar) substrates such as metal20 and painted steel surfaces but generally exhibit lower adhesion to low energy (i.e., nonpolar) substrates such as p~ LhJI~ . and pol~ lc~
Solvent-processed acrylic PSA ~ . can be crosslinked by adding a polyrul...Liu..al ~ " ' ,, agent that reacts with a reactive group present in the polymer. See, e.g., Japanese Kokoku 58[1983]-û46236 in which is described a 25 solvent-processed crosslinked acrylic PSA with exceDent cohesion that is the reaction product of (a) a pol~: , , prepared by reacting ( I) an acrylic copolymer having a molecular weight between l,ûOû and 3û,000 and from 1.7 to 5.0 functional groups that can react with an isocyanate group with (2) a u' ~Cy~ t~" so that the ratio of isocyanate groups per coreactive functional 30 group is about 2: 1, and (b) an adherent copolyrner comprising functional groups that can react with an isocyanate group. Like any solvent processing technique, however, the ~" q,~ Liu.. of thick adhesives is difficult because the solvent causes bubbling in the adhesive and the emission of solvent vapors into the ~ '~~~ ~ . ' ~ is u..i~ vlc.

wo96/05249 ,~ p l ~ " 2 1 9 6 ~ 73 : 2 To avoid e..v;.U. 1l.,..~1 pollution" - r 1..l;."~ processes that do not require the use of volatile solvents have become of great interest. An early step in this direction for the ~ t of PSA tape was the process described in Belgium Patent No. 675,420. In this process, flexble carriers are coated with 5 acrylic monomers, or mixtures of such monomers with cuyvlJ...~,i~l,l~, ~Wl r ' with the possible addition of a thickening and/or initiating agent, and the monomers are pul~...~,.i..~d directly on the carrier using ultraviolet radiation.
Hot melt coating a PSA ~ eliminates the necessity of solvent processing. To hot melt process an adhesive ~ u- 'I ;n.~, the, , must lo be Ul~ '' ' ' during the coating process; however, to achieve a PSA with balanced properties (i.e., peel and shear adhesion), the , rnust be crosslinked. In hot melt coating processes, this is usually done by exposure to high energy radiation (e.g., E-beam or high intensity ultraviolet radiation). When high intensity ultraviolet radiation is used, a I ' . ~. ". ua L~ species such as ~ is generally added to the ~ . ~ ~ However, thicker sections of PSA ~ - cannot be cured this way.
A more efficient method of r~ u ~ L~ involves hl.~ul~Julc~
hydrogen abstracting moieties into the polymer backbone prior to coating. Such polymers can be hot melt coated and ~ ly cured by Cul irradiation techniques. This process is typified by U.S. Patent No. 4,737,599 where a PSA with good adhesion to skin is described. That process is much more eflicient than the high rntensity irradiation method described ~ ' 1~ above.
The cohesive strength of an acrylic PSA can be increased without unduly affecting its compliance by utilizing a I ' .~. .,., ' ' ~ ~ agent in .; with a l ': ~ . See, e.g., U.S. Patent Nos. 4,181,752;
4,329,384; 4,330,590; 4,391,687, and 5,202,361. Useful l ' v~ "l~ - ' ' ~
agents include various aldehydes, quinones, and particularly certain .,1.., , ' e-substituted ~ ' ' j1 s triazines (because they provide desirably shortened reaction times and somewhat greater tolerance to oxygen over the non-30 L ' ' ' .y containing agents), although their use can result in evolution of HCI
during pv1~.".,.i4~1iu...

wo 96105249 , ' . ~ ? Q t ~ P~ 5~

An ultraviolet (UV) radiation-curabie u~ u~ that includes 20 to 99%
(by wt.) of a copolymer of ~lh.~ ' monomers, I to 80% (by wt.) elhJ' ~ "~, ....- - ... rl r- I monomers, and 0 to 20% (by wt.) of one or more pol~ ILjh,.~ y~ YIrd r ~ isdescribedinU.S.PatentNo. I
s 5,180,756.
CopGl~ .,l Lal,le I ' ~ such as 2-[4-(2-hydroxy-2,2-dimethyl-1-oxopropyl)phenoxy]ethyl 2-propenoate and their use in the pG~ -I ;~ ' of h,h,llh,~ ull~alul ' ~ , ' is disclosed in U.S. Patent No. 4,922,004.
Japanese Kokai 2[1990]-248482 describes a I 1 .lu ~ PSA obtained o by reacting (a) 30 to 50 parts by weight (pbw) of a copolymer of an acrylic acid alkyl ester, a CU~UU~ Ie c;lh.~ u ~ yl rrl monomer having a polar group, and a copol~.. ;~al/le monomer with a I ' ~ group (such as 2-a~,lyluylw.y~ ~ ' or l-a.,.yluJlu,.y-2-[4-(4-.,1 iu,ube.~uyl)ben20yl-oxy]ethane); (b) 40 to 60 pbw of an aryloxy acrylic monomer such as 15 ~ .IL.~I acrylate or null~ hyl acrylate; and (c) a tackifying resin.
The - r - iS cured using a total dose of energy of 300 to 800 mJlcm2 from a high pressure mercury lamp. Such high intensity ultraviolet radiation is iikely to produce an adhesive that has a shear value less than 100 minutes.
Similarly, DE 42 03 183 Cl (Germany) discloses a method for producing 20 PSA layers comprising the steps of thickening a monomer mixture that includes a 1,l,,,l,,;..;l; ~ ~. with a separately made, solvent-free saturated W-reactive pc,l.~al,l~;dt," coating the thickened rnixture onto a substrate; and irradiating the coated substrate. The separately made polymer comprises side chains that, when irradiated, participate in .,. ~ reactions. The soie example involves the 25 addition of a ~UIIIJII.~I .,;..11~ available polymer having a molecular weight of about 200,000 to a monomer mixture that is then pol~lll. .~1 The shear vaiues of PSAs prepared by actinically irradiating acrylic monomers can be enhanced by the addition of polyacrylic u - U~ ;lllLIlg agents.
See, e.g., U.S. Patent No. 4,379,201. Such PSAs involve networks and are 30 sensitive to processing conditions.

W0 96/05249 2 1 ~ 6 1 73 P~

A ~ that can be radiation cured to provide thick, high molecular weight PSA u~ with ~ properties has not been previously described.

Briefly, the present invention provides a syrup, preferably a syrup of a coatable viscosity, curable to a crosslinked ~ .u ~ material, a) about 65 to 99 9 weight percent, preferably about 90 to 99 weight percent, of a solvent monomer mixture comprising about 95 to 99.9999 pbw, preferably 97 to 99.995 pbw, of at least one free radically-pulJ.. ,, Udl le e~h~ uu~Luldkd monomer and O.ûOOI to 5 pbw, preferably 0.005 to 3 pbw, of an eLhJ ' ~ . . . t Z monomer comprising a I dd;l~iU.. scnsitive hydrogen abstracting group;
b) about 0.1 to 35 weight percent, preferably about 1 to 10 weight percent, of a solute polymer having a molecular weight of at least 500,000, which polymercomprises about 95 to 99.999 weight percent mer units derived from one or more free radically-pul,l.l.,.i~le ~:lh~ l monomers and about 0.001 to 5 weight percent mer units derived from an ~ ' monomer comprising a r~ inr ~ ~ vl: hydrogen abstracting group;
c) from 0 to 5 pbw, preferably 0.01 to 0.30 pbw, of a free radicaUy-pGI,y ' ' ' PC~ 1hJ~ V I ' ' ' monomer; and d) from 0.0001 to 3 pbw, preferably 0.001 to 1.0 pbw, of a saturated energy-activated initiator of p~ (i.e., an energy-activated initiator of pG~ d~iUn that is free of ethylenic ~ ) In another aspect, the present invention provides a process for making a crosslinked ~I ....,. 1_~1....-- ~ i-, material comprising the steps:
a) providing a u~ comprising a solvent monomer mixture comprising at least one free radically-pGl),....,,;~dlle ethylenically -- -n..
monomer and 0.0001 to 5 pbw, preferably 0.005 to 3 pbw, of an ~h~
30 1l~- u~ rd monomer comprising a radiation-sensitive hydrogen abstracting group and 0.0001 to 3 pbw, preferably 0.001 to 0.5 pbw, of a saturated energy-activated W0 96105249 . P~ . C, ~
~ ~ 5 21 961 73 initiator of pu'J....,.i~Lun, preferabiy a saturated radiation-activated initiator of b) exposing the ~ 1~~ to energy, preferably radiative energy, so as to partially polyrnerize the monomer mixture and form a coatable syrup;
c) adding to the syrup, based on the totai amount of monomer initiaily present in the monomer mixture, 0 to 3 pbw, preferably 0.001 to 0.5 pbw, of a saturated energy-activated initiator of pul~ , preferably a saturated radiation-activated initiator of pu'~ , O to 3 pbw of an e~h~
' monomer comprising a radiation-sensitive hydrogen abstracting 0 group; and/or 0 to 5 pbw, preferably 0.01 to 0.30 pbw, of a PUI~1}IJ~
dkd monomer; and d) exposing the syrup to energy that activates the initiator and the radiation-sensitive hydrogen abstracting group so as to form the crossliniced ~ ,..oF~ . materiai.
The crossiiniced ~t ' material produced from the above syrup is also described. The syrup optionally can be coated on a substrate prior to being irradiated, and such articies are also described.
The coatable syrup of the present invention is pol~ ...~,.i~l,l_ to a ~:- Of 1~l",,,. .;. material that can be crossliniced directly or hot-melt coated (for 20 example, when no pol~.,Lh,~ ' monomer is present) and then ~,.. " ' ' The~:- uFI~ materiaiispreferablyaPSAhavinghighshear at both ambient and elevated t~,...~,.,.~Lu..,~. This syrup comprises a solute polymer in a solvent monomer mixture. The polyrner preferably has a very high molecular weight, preferably at least 500,000, more preferably at least 750,000, even morepreferably at least 1,000,000, most preferably at least 1,500,000. One or both of the polymer and monomer contains at least one roA;o~io- S~ ;tive hydrogen abstracting group that, upon exposure to UV radiation, is activated to enable curing. The cured product is a crossliniced ~ u- 1 ~ . . ;. . materiai.
The polymer of the syrup of the present invention contains side chains that 30 comprise ' scnsitive hydrogen abstracting groups activatable by UV

wo s6/0s24s . P~~ v2 6 2~96~73 radiation, resulting in a crosslinked \, S product (i.e., essentially one crosslinked u~ u~l~ole~ulc, not an hlLcl~ Lh~g network).
Where no eLh.~ ' monomer comprising a radiation-sensitive hydrogen abstracting group is present in the initial monomer mixture, 5 some polymer that includes side chains comprising the ~ul, ' radiation-sensitive hydrogen abstracting groups or some monomer that contains a radiation-sensitive hydrogen abstracting group must be added to the syrup prior to formation of the ~ . Of l_~n ~ ~ ;' material therefrom, i.e., pol~....,.i~Liu.. of the monomer(s) of the monomer mixture. Preferably, however, the solute polymer is lo prepared in situ, i.e., directly from the solvent monomer mixture. This eliminates the need for solubilizing a separately made polymer in a monomer mixture and allows very high molecular weight polymers to be formed and solubilized.
Crosslinked ~ .~ u 1 ~l .. ;1 . materials produced from the syrup of the present invention can be used as PSAs, vibration damping materials, transfer adhesives, structural adhesives, protective coatings, and the like. AJ~u,L,,_~Ju ,1~, the syrup of the present invention can have a coatable viscosity and can therefore be applied to a substrate prior to curing, thus allowing for the simple production of articles comprising one or more layers of the ~ul, ' ~ ' material.
Unless otherwise indicated, the following definitions apply in this 1. , .
fllJr "group" or ~COIIIIJUU~J'~ or "monomer" or "polymer" means, unless otherwise noted, a chemical species that can be substituted by cu..,_..:iu~
that do not interfere vith the desired product; and 2s "(meth)acrylic" refers to acrylate, ' yL.Lc, acrylamide, and ~ ' ' cnmro..~1s, as well as alkyl and aryl compounds that have been substituted with an acrylate or u~.,L;.v~ ' group.

wo96105249 ~ S 21961 73 r~

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The syrup of the present invention comprises from about 65 to 99.9 weight percent, preferably from about 90 to 99 weight percent, more preferably from about 93 to 97 weight percent of a solvent monomer mixture and from about 0.1 5 to 35 weight percent, preferably from about 1 to 10 weight percent, more preferably from about 3 to 7 weight percent of a solute polymer.
In the syrup of the present invention, the solute polymers and the solvent monomer mixtures are based, in substantial part, on free . ' ~ pGI~
tLh~ all.~ u~ lul ' monomers. ElL,' ~ '1~ I ~l~ monomersthat do 0 not contain a radiation-sensitive hydrogen abstracting group comprise from about 95 to 99.9999 pbw, preferably 97 to 99.995 pbw, ofthe monomer mixture. From 95 to 99.999% (by wt.) of the mer units of the solute polymer also are derived from suchmonomers. Preferredfreeradically-pol~ clh~
~t~d monomers are (meth)acrylic acid and its numerous well known 15 derivatives.
Particularly preferred among such monomers are ~ ' ,' ~ '1~
d monomers that are I r ~ u to a polymer with a glass transition t~ UI~ (T~) less than about 0~C (hereinafter "A ").
These monomers preferably constitute from about 50 to 99.9999 pbw, more 20 preferably from about 60 to 95 pbw, of the solvent monomer mixture of the syrup of the present invention. Common examples of A monomers include (meth)acrylic acid esters of Illù.lVL~ dl ;~ alcohols. Preferred among these are esters of non-tertiary alcohols, p~ l;~,ulall~ primary alcohols. Those (meth)acrylic acid esters wherein the alkyl pûrtion of the ester contains from 4 to about 12 25 carbon atoms have been found to be especially useful. Such monomers include, but are not limited to, isooctyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, decyl acrylate, and dodecyl acrylate.
Mu~ , ' monomers that are ho.ll,)pol~ ,.i~lle to a polymer with a T~ greater than about 5û~C (hereinafter "B lul)llJ...~") can also30 be included in the free radically-pol~ .i~le dhJ~ portion of the monomer mixture of the ~,u ~ . of the present invention. B monomers, w0s6/0s249 I C P ~ 11 96 1 73 P~ 2 when present, preferably constitute from about 0.1 to about 50 pbw, more preferably from about 5 to about 40 pbw of the monomer mixture. Examples of useful B monomers include, but are not limited to, (meth)acrylic acid, itaconic acid, substituted (meth)a~.~' ' such as N~N-dh~ LhylG~ ' and N-5 O~ljlr~ ' ,N-vinyl IJJ~ , N-vinyl~..uk.~,l~--,a~lylv.
l~lldLJII~ r r yl acrylate, isobornyl acrylate, abitol acrylate, and L,~lcr ~ ~ acrylate.
ElhJ' ~ monomers that comprise a radiation-sensitive hydrogen abstracting group and that are cul,vl~ ' ' with the drv o free radically-pol.~...~,.i~l~. c:LhJ~ " dLC:d monomers (hereinafter "C
monomers") can constitute from 0.0001 to about 5 pbw, preferably 0.005 to 3 pbw, of the solvent monomer mixture of the syrup of the present invention.
Monomers that comprise a radiation-sensitive hydrogen abstracting group are thought to promote .,., " ' ~ of the backbone chain of the polymer (as opposed 15 to formation of pendent poly~ner chains). Preferred C monomers include ~Lhy~ U~ in~d compounds having the general formula 1~l ~ 1 CH~=~' cX~ )A~ )bff~)c~;~Z
, n wherein R is H or a Cl to C3 alkyl group, preferably H or a methyl group;
X is O or NH;
nisOorl;
m is O or an integer from 1 to 5;
a, b, and c are ;..1. p. L lly O or l;
M' is CH2 or SiRIR2;
M2 is CR3R4 or SiR'R2;
M3 is 0, NH, C(O), C(O)O, C(O)NH, or OC(O)NH;
RZ and R2 are ;~ p L - ~ly H or a Cl to C~ alkyl group;

WO96105249 r~ h Q ~ ~ 2 1 9 6 1 73 1~

R3 and R~ are ~ 1y E[, an alkyl group having 1 to 14 carbon atoms, a cycloalkyl group having 3 to 14 carbon atoms, an aryl group having 5 to 12 ring atoms, an arenyl group having 6 to 26 carbon and 0 to 3 S, N, and nu~ " u~ hl;l, O het~,, ualu... " or R3 and R~ taken together with the carbon tû which they are attached form a carbocyclic ring containing 4 to 12 ring atoms;
G is a covalent bond, (CH2)d, or ~CH2)dO where d is an integer from I to 4, preferably from I to 2;
Z is a ~ad;aliù.. ~ ve hydrogen abstracting group having the general lo formula --Ar--C--R' R' in which Ar is a substituted arene having 6 to 12 carbon atoms, preferably a b~ iyl group;
R5 is hydrogen, a Cl to C~2 alkyl group, a C~ to C~2 alkoxy group, or a phenyl group; and R6 is a C, to C6 alkyl group, a cycloalkyl group having 3 to 14 carbon atoms, or ~R7 R' wherein R7 and Rt are ~ ', ' ly selected from the class consisting of hydrogen, Cl to C12 alkyl groups, Cl to Cl2 alkoxy groups, and phenyl groups, with the proviso that, when R' and R' (or R8) are ortho to the carbonyl group of. Z, together they can be one of --O--, --C--, --S-- and ~H,--w096/05249 ~ ?P~t~ 2~96173 Preferably, where m is not 0, both M' and M~ are not SiRIRZ.
Included among those hydrogen abstracting C monomers . -- . - ~ = 1 by Fonnula I are those where Z is a moiety derived from one of the following r--1l ' (or a substituted derivative thereof~:

D

~ ~~
5,12 ,' ~ &~,~.,G.I~

benz(A) ' 7,12-dione 1,4,,1..~ , 6,13 F . 5,7,12,1~1 ~,.. c wo s6/0s24s , ~ Ç) ~ F~~
~ t ~ 2' 961 73 9-fluorenone anthrone 1~ ~

X = O (~nthone), Aih~n~cllh, S(' ' ),or NH (acridone) chrc,rnorle In most of the above structures, the bond to G is preferably located para to the 5 bridging carbonyl group.
The synthesis of C monomers having the fommula 0 R' 0 CH2=CI--CNH(CH2)b--I--CO--Z
R R' (and related c.~ .uu I~ where other atoms and moieties replace the oxygen atom between Z and the carbonyl group) is described in assignee's copending PCT
application(AttomeyDocketNo. 51911PCTIA).

wos6/0s249 ~ p r ~ 2 ~ 961 73 ~ 5~

In general, these ~ - r ~ can be prepared by reacting a 2-alkenyl aziactone and a ~'''rlr~U~ group-substituted carbocycle compound (such as those set forth above). A variety of other C monomers can be made by reacting an ~Ih,' "y l ' compound comprising a first functional group 5 (hereinafter "D . , ' "~ with a compound that comprises a radiation-sensitive hydrogen abstracting group and a second functionai group (hereinafter "E ,:1., ' "), the two functionai groups being coreactive with each other.
Preferred D and E 4-- 1 U ~ are eLh,' 'l~ ~ ' aiiphatic, .,y.' li, ' ~, and aromatic -~ r ~ having up to 36 carbon atoms~ optionaily o one or more oxygen and/or nitrogen atoms, and at least one reactive functionaigroup. When the first and second functionai groups react, they form a covaient bond and linic the D and E c,. .p~
Examples of useful functionai groups include hydroxyl, secondary amino, aziactyl, oxazolinyl, acetyl acetonyl, carboxyl, isocyanato, epoxy, aziridinyl, acyl 15 haiide, vinyloxy, and cyclic anhydride groups. Preferred among these are isocyanato, hydroxyl, carboxyl, and vinyloxy groups. Where the D or E
compound comprises an isocyanato group, the other preferably comprises a secondary amino or hydroxyl group; where the D or E compound comprises a hydroxyl group, the other preferabiy comprises a carboxyl, isocyanato, epoxy, 20 anhydride, or aziactyl group; where the D or E compound comprises a carboxyl group, the other preferably comprises a hydroxyl, amino, epoxy, vinyloxy, or oxazolinyl group; and where the D or E compound comprises a vinyioxy group, the other preferably comprises a carboxyl group.
R~ ' v~ examples of usefiul D r _ ~ include h~ Jl w~y " yl 25 (meth)acrylates such as 2 i~1dlu~ yl (meth)acrylate and 2-(2 I.~JIU~
oxy)ethyl (meth)acrylate; aminoalkyl (meth)acrylates such as 3 r U~
(meth)acrylate and 1 . - ~ ,; azlactyl-substituted crmrolmrlc such as 2-ethenyl-1,3-oxazolin-5-one and 2-propenyl-4,4-dimethyl-1,3-oxazolin-5-one;
carboxy-substituted 4UIII~U. ~ such as (meth)acrylic acid and 4-w-l,u~.~b~,.. zyl 30 (meth)acrylate; isocyanato-substituted compounds such as isocyanatoethyl (meth)acrylate and 4-;su~,~. ,. ' ' yl (meth)acrylate; epoxy-substituted .

Wos6l0s249 ;' ~ t ~ s such as glycidyl (meth)acryiate; aziridinyl-substituted ~ J" I~ such as N-a~.lyl~JjL~Ii ihl~ and 1-(2-propenyl)-aziridine; and acyl haiides such as (meth)acryloyl chioride.
RGIJI ~ ~ ~ examples of E ~ . ' include functionai group-5 substitutedhydrogenabstracting, , ' suchas(q hJJI~ Y~ ' Yl)-r J , (~ ,1 hJJI~ Y~ ' Jl 1 u~.yl ' ~ 2 ~ ".yl ' ~rl 2,4-~' ' yl ' ,' ' ~, 4-iso.,y ~ 1 q r ,~ ~, 2-llyJl~lAy , 2 }~ u~yi xanthone, and 1 hJ~ .y o Examples of C monomers prepared from D and E , ' are given below in Table I. Those sicilled in the art will recognize the starting materials used for each listed C monomer and how other C monomers can be prepared through the use of other coreactive D and E ~' l'~

Table I: Examples of C monomers CH,= IC--CNH--IC--CO~ CH,--CH--CO--CH,CH,--OC~
CH, CH, ~H, C ~3 ON ~o~ic~cH~

CH,~eO--Cii,CH,--OC~ CH,--CH--CO--CHjCH,Nl~CH~

Preferably, a saturated energy-activated initiator of p~ ....,.i~;u., ~I.e., a source of free radicais other than a C monomer) is used in forming the polymer wo96/05249 ~'i.'~. t r~ 2 ~ 96173 component of the syrup of the present invention from the solvent monomer s - , These energy-activated sources can be either heat- or W radiation-activated. Examples of heat-activated sources include benzoyl peroxide, t-butyl p~ , cumene hyd~ul,~,.u~ud~" azobis~l~ul,uly.u...tl.l,,), and methyl ethyl5 kl:lu~.~.u~d~,. Useful W radiation-activated initiators include the benzoin ethers such as benzoin methyl ether and benzoin ispropyl ether; substituted ~ ' such as 2,2-di~,lhu~-~ r~ , ~.u~ li,r available as IrgacureTM 651 1 ' (Ciba-Geigy Corp.; Ardsley, NY), 2,2-dimethoxy-2-phenyl-l-~,l.~,.., 1~1IIGIIOIIe~ available as EsacurelM KB-I photo-0 initiator (Sartomer Co.; West Chester, PA), and d ' yllydlu~substituted a-ketols such as 2-methyl-2-hydroxy ~ , aromatic sulfonyl chlorides such as 2-l . ' " ' "' rl chloride; and l,lLuluv~livc oximes such as l-phenyl-1,2-1..,. ' -2-(O-clllw~y~,~LllJu..J')oxime. Particularlypreferred among these are the substituted ac- n .l .l . A saturated energy-activated source of free radicals can be present in an amount from 0.0001 to about 3 pbw, preferably from about 0.001 to about 1.0 pbw, more preferably from about 0.005 to about 0.5 pbw, per 100 pbw ofthe solvent monomer mixture.
When present and upon activation through ;Illl UdU~l;Un of ~ ,lu~Jl;dtc energy, the saturated energy-activated initiator of pGi~ ;UI~ initiates the 20 pol.~ ..~l;onofthefreeradically-pul~ ~bleelllJ' ~ '1~, monomers ~I.e., the A and B monomers). When c~h,' '1~ ~ ' monomers comprising a radiation-sensitive hydrogen abstracting group (i.e., C
monomers) are also present, they also can be ~ IJul alcJ into the backbone chainof the polymer, resulting in radiation-sensitive hydrogen abstracting groups 25 pendent from the backbone chain.
Where a saturated heat-activated initiator is used with a monomer mixture that includes at least one C monomer, the syrup can be exposed to heat only or to heat and W radiation so as to initiate pul.~ of the monomer mixture.
Inclusion of UllXltUl a~td a-cleaving monomers and/or pol ~. ' 30 monomers will provide a polymer with pendent groups that include a-cleaving or U 1- -I ~ 1 groups"~ . Those groups can then be activated by means w09610s249 ; ~ f g ~ v>
~ 2 1 9 6 1 7 3 known in the art to allow for further pGI~ ' " , normally after the monomer-polymer . . (i.e., syrup) has been coated onto a substrate.
One or more free radically-pol.~ ,i~le pul~_.hJ' monomers can be included in the monomer mixture or, preferably, added to the 5 syrup Use of such monomer(s) allows for a reduction in the amount of ~ ~"~ .t. d monomer comprising a ~. " s ~ fivc hydrogen abstracting group necessary to produce the ~- l; I material of the present invention. Examples of POl~ ~1hJ~ , ' monomers that can be used include, but are not limited to, polyacrylic-functional monomers such aslo ethylene glycol diacrylate, IJIU~Jk~ J~UI J~ lla~ Lt~" i ' JIUIP~
triacrylate, I,6 1- ~ yl~ ' . F ytluilul di-, tri-, and lcllaa~u~llak:~ and 1,12-doA~ rl diacrylate; olefinic-acrylic-functional monomers such as allyl ~ La~ , 2 ~k"~y.,al~ ~' ' ' Jl l.._~La~
and 2 "~,' - ' J: acrylate; allyl 2-acrylamido-2,2-~" ' yla~,etaLc~
5 d;~ Ib~~.,.l~" and the like.
If desired, ~ ~ O can be added to the syrup of the present invention.
When I ~ UD~ D are used, the resultant v; I; t( i., materiad has a foam-like ~pp~r~n~e These lIU~IUD~JL-~D can be made from materials such as glass and polymers.
Glass llJ~luDIJh_~cD, as described in U.S. Patent No. 4,223,û67, can have an average diameter of from about 5 to 2ûû mm, preferably from about 2û to about 80 mm. Such lIU~IUD~IL~CD can comprise from S to 65% (by vol.) ofthe material of the present invention. Preferably. a coated layer of the ~ material is at least three times as thick, preferably at least seven times thick, as the diameter of the glass ~ . ' CD.
Alternatively, hollow polymeric , . ' ~D having average diameters of from 5 to 200 mm can be blended into the syrup of the present invention in amounts of from about 15 to about 750/D (by vol.) prior to coating. Where such polymeric llU~l uD~JL_. CD are used, they can be added into the syrup in an , ' ' form and ~ .. ;ly heated to cause expansion. However, expanding them prior to addition is generally preferred because this helps to WO 96/05249 ~ 1 O ~ 1 7 7 r~
L I ~ J

ensure that the hollow ...;.", . ' tD are ' "~, surrounded by at least a thin layer of \,;~ n ~ . ; material in the final article. Useful polymeric lld.~luD~ D are described in U.S. Patent Nûs. 3,615,972, 4,û75,238, and 4,287,308. Hollow polymeric UDIJh~ D are available under the tradename ExpancellM (Eka Nobel Inc.; Marietta, GA). In expanded form, they have a specif c density of a~ 0.02 to 0.036 g/cm3.
A particularly useful adjuvant is fumed silica, especially hJ.llu~ vb;~, silica as disclosed in U.S. Patent Nos. 4,710,536 and 4,749,590. In another . ~ - " of the present invention, a layer of the ~ u I ~ . ;. material can contain from about 2 to about IS pbw of hylllu~ vb;c silica having a surface area of at least 10 m2/g.
Other usefiul adjuvants that can be blended into the syrup of the present invention include fillers, dyes, pigments, plastici2ers, fibrous reinforcing agents, woven and nonwoven fabrics, foaming agents, a ' , stabilizers, fire retardants, tackifiers, electrically conductive particles and viscosity adjusting agents. If so desired, chain transfer agents can also be added so as to keep themolecular weight of the solute polymer below a desired value. Those skilled in the art with recognize that the amount of such adjuvants can vary from about 0. I
to 50% (by wt.), depending on the desired end use.
Although ~ ' - films can be prepared directly from the solvent monomer mixture (by quickly pvl~ ~ ~ a coated layer of the monomer to a pvl~ l mrsture), increasing the viscosity of the monomer mixture to a level more suitable for coating is preferred. This is readily - . ~ ' ' by exposing the monomer(s) to a source of energy until about 0. I to 35~/O (by wt.), preferably about I to 10% (by wt.), more preferably about 3 to 7% (by wt.), of the monomers have pol~....,..L~I. If the source of energy is heat, a heat-activated initiator of free radicals can be included in the ~ If the source of energy is W radiation, a radiation-activated source of free radicals can be usedbut is not absolutely required where a monomer of the monomer mixture contains 30 a radiation sensitive group that produces free radicals on exposure to suitable WO 96/05249 ~ ,C 2 1 9 ~ 1 7 3 radiation. Use of a radiation-activated source of free radicals is preferred in such situations, however.
The , (i.e., syrup) ofthe present invention is preferably prepared in sifu by mixing one or more free radicaily-p~ ..~dl,lu cLl~
5 , ' monomers and 0 to 3 pbw of one or more of the above-described C
monomers and then pol~ the monomer(s) to form a solute polymer. The monomers can be added in any order. Where no C monomer is present in the monomer mixture from which the syrup is formed (i.e., no la i;aLiu.. ~, hydrogen abstracting groups are present in either the solute polymer or the solvent monomer mixture), some of these groups must be introduced into the syrup prior to formation of the ~ o~ material. This can be done by adding C
monomer to the ~ , ~ after formation of the solute poiymer or by adding to the syrup a second polymer (made separately from the syrup) that contains mer units with the above-described . ' ~ ~ ~, hydrogen abstracting groups pendent therefrom. Adjuvants, when desired, can thereafter be blended into the mixture.
The in sifu plt~ aL;u~ of the c~ just described ailows for the production and ' ' ' ~ of very high molecular weight polymers. Such polymers preferably have a molecular weight of at least 500,000, more preferablyat least 750,000, even more preferably at least l,000,000. most preferably at least l,500,000. The ! ~ ' ~'- ' ~ of a separately made polymer of such a high molecular weight is very difficult. Therefore, the above-described in si~u aLiGn method is the preferred manner of maicing the ~ of the present invention.

2~ A syrup of a coatable viscosity can be applied to a substrate, preferably a fiexible carrier web, using any .,u.... ' coating means such as roller coating, dip coating, icnife coating, and extrusion coating. The substrate can further comprise a release coating between the substrate and the syrup or on the side ofthe substrate opposite the side on which the syrup is coated.
Once a syrup has been prepared, a crossliniced ~ Osis~ materiai can be prepared therefrom in a variety of ways. In each method, however, the w096/05249 ~. 2 ~ 9 jr ~ ~ ~ ~ t ~ 6 1 7 3 remaining monomer(s) in the syrup are pol~ ' by exposure to radiation that activates the hydrogen abstracting groups and facilitates ~,l ua LLIl~.
One way to make the ~ ;. materiai from the remaining monomer(s) is to irradiate the syrup with both high and low intensity W
5 radiation. Low intensity radiation is defined as 10 mW/cm2 or less (as measured in accordance with procedures approved by the United States Nationai Institute of Standards and Technology as, for example, with a WIMAPTM UM 365 L-S
radiometer ~ "~lrd~,lulcd by Electronic L.~.., - & Technology, Inc., in Sterling, VA), preferably in the wavelength region of 200 to 600 nm, preferably lo 280 to 400 nm. High intensity radiation is defined as anything greater than 10 mW/cm2, preferabiy between 15 and 450 mW/cm2 When such radiation is used, the ~ .", i. materiai can be formed directly from the syrup.
Other ways of making the ~1,~ ,, l_~m - .. . ;r material involve initiaily exposing the syrup to oniy low intensity radiation. Syrup r. " ., ., .1 - o .~ that 15 produce high p, r ~ ~ ' materials wiii depend on the particular crosslinker (i.e., C monomer) and its abiiity to be activated by the particular radiation used. Generaily, where the percentage (by wt.) of mer units derived firom the C monomer is about 0.2% or greater and C monomer is used in .,, j, 1;.. with a pol~,LI..~' ~y, ' monomer (e.g., a ' acrylate), this low intensity exposure is sufficient to make a ~i ' ;u material with balanced PSA properties. Where the percentage (by wt.) of mer units derived from the C monomer is less than about 0.2%, however, further processing is preferable. Specifically, exposure to low intensity light is preferably followed by exposure to high intensity radiation so as to form a crosslinked ~ o l~l o . ;c materiai having baianced properties.
rul~ .i~Liùn is preferably performed in an inert ~I.e., oxygen free) r--- . ' c, such as a nitrogen atmosphere. Tolerance to oxygen can be increased by including in the syrup an oxidizable tin compound, as is taught in U.S. Patent No. 4,303,485, the teaching of which is ~u~dLcd herein by reference.
The syrup of the present invention can be cured in air by covering a layer of the ~ , coating with a plastic film that is sub >~ ;dll~ transparent to W096105249 ~ r ~ ~ 0~ 9 S ~

W radiaeion but impervious to oxygen and irradiating the C ~ ~~ through that f Im using W lamps that emit light in the ~ ,I.,..o;h range ~,O~ to the absorption maximum of the hydrogen abstracting groups and saturated i ' . Several different ~ "~, available lamps, including medium 5 pressure mercury lamps and lu .. Iy f uorescent lamps, can be used. The radiation intensity of these lamps is preferably adjusted so that the radiation intensity at the surface of the coating is less than 20 mW/cm2, preferably 0.5 to 6 mW/cm2, each having emission maxima between 200 and 600 nm, preferably between 280 and 400 nm. Maximum efficiency and rate of pol~ is o dictated by the ., ' ' ,, between emission properties of the radiation source and absorption properties of the i ' ~ ~, c ~- ~l u~ employed.
Where the saturated energy-activated initiator in the syrup of the present invention is heat-activated, the syrup preferably is exposed to a heat source either before or - - .. ~ v~ with exposure to radiation of a ~ ' that activates the hydrogen abstracting groups present in the monomer andlor the polymer of thesyrup.
Where the energy z_livd~cd initiator in the syrup of the present invention is a saturated W radiation-activated initiator, the syrup preferably is exposed first to a ~ ' of radiation that activates the saturated initiator until the monomers polymerize to a coatable viscosity so that the syrup can be coated on a substrate.
This coated c~ is exposed to radiation of a ~ ' to which at least the hydrogen abstracting group of the C monomer is sensitive at an intensity of less than 10 mW/cm2 (for a total dose of 30 to 800 mJ/cm2) so as to fi~rther polymerize the monomers as well as crosslink the polymer chains.
Extent of polyl~ liu~l can be monitored by measuring the refractive index of the adhesive layer. Refractive index is a sensitive measure of the extent of pol~ ,, i~lion. This method is commonly applied in pol~ ;UA. kinetics work. See, for example, discussions about the method in Pul~ , . at Advarlced Degrees of conversion, G.P. Gladyshev and K.M. Gibov, Keter Press, Jerusalem (1970).

WO 96/05249 r~

Where the crosslinked ~,; ' i., material of the present invention is a PSA, it displays balanced properties (i.e., a good ' ~ of adhesion, cohesion, ~1., ' , and elasticity). This is believed to result from the crosslinked nature of the \,: ,~ u I -~n ... ,..; material. Crosslinking in the present 5 invention is quite different from the ~u..~ liu.lGI mechanism of .,.~
provided by diacrylates where an increase in of diacrylate results in a reduction in peel adhesion strength without an increase in static shear strength.
A ~ulLiL~ iJ tape that includes at least one cured layer derived from the lo syrup of the present invention is also within the scope of the present invention.
Such tapes can have a thin layer of a different pressure sensitive adhesive laminated thereto, so that the adhesive of the invention is being used as a backing or core layer. The additional layer(s) can be any uu..~. ' adhesive known in the art; however, (meth)acrylic adhesives are preferred. Such, ' ', _. ~;d 15 ~,o5tlul,liull~ can be prepared by processes disclosed in U.S. Patent Nos.
4,818,610,4,894,259, and 4,895,738, the teachings of which are ~u. al~d herein by reference More preferably, additional adhesive layers include polymersof at least one alkyl (meth)acrylate monomer and a ~,UpGl~ ' ' ' monomer hu~ ul~l_fi~k, to a polymer with a T~ above about 50~C.
Multilayered tapes where a layer of a poly~ldll.,l._, pul~, ' ' Opl.~l._, polyacrylic foam, or pul~ _Ih~ k,.l~, foam on which is coated a layer of the u. ~ material of the present invention are also possible. Such tapes are often used to attain very high bond strengths. Further r " about such u.,Lo..i can be found in, for example, U.S. Patent Nos. 3,565,247, 3,993,833, and 4,415,615, the teachings of which are h~ol~ol al~J herein by reference.
When the coated films of the present invention are cured, they preferably have a percent gel (corrected for any soluble tackifying resins and other additives) in the range of from 2 to 95% (by wt.), more preferably from 30 to 90~/o (by wt.), and most preferably from 50 to 80% (by wt.) wos6/0s24s .~ 2 ~ j r~

The ~ of the present invention can also be used to make a cellularPSAmembraneasisdescribedinU.S.PatentNo.4,415,615,theteaching of which is ~,o~ d herein by reference.
Objects and advantages of this invention are further illustrated by the 5 following examples. The particular materials and amounts thereof, as well as other conditions and details, recited in these examples should not be used to unduly limit this invention.

EXAMPLES
The following tests were used to evaluate PSA tapes made from syrups of the present invention.
A Static Shear Strength Stainless steel substrates were cleaned once with acetone and three times with a 50:50 water ;~ . ' solution.
IS The adhesive films described in the examples were cut into 2.54 cm x 1.27 cm strips and adhered to the pieces of stainless steel for about four hours. A 0.13 mm anodized aluminum backing was used for each of the adhesive samples.
Each sample was placed either at room t~,...l,.,.~u,~ (RT) or in an air-circulating oven that had been preheated to 70~C. A weight was hung from the 20 free end of the tape, with the sample tilted 2~ from vertical to eliminate any peel forces. Two tests were performed for each adhesive sample and the average value is reported in the examples below. The time (in minutes) at which the weight fell was designated the static sheet RT (1000 g) or 70~C (500 g). The test was d ~ ; .. d after 10,000 minutes if no failure had occurred.
25 B. Peel Strength Unless otherwise indicated, l..~ul~,....,.~b were made using a 90~ peel mode at 30.5 cm/min. In the examples below, results are in N/dm.
Pieces of stainless steel were washed once with acetone and three times with a 50:50 water-i~u~.l, r ~ solution. Each adhesive film was adhered to a 30 stainless steel backing for three days prior to being tested. Each sample was about 1.3 cm wide and had a 0.13 mm anodized aluminum backing (about 1.6 cm wide).

w096/ 5249 ~ 2 1 l~11VV ~VL
, 9 6 1 7 3 Examples 1-7: Awylu,.~
To a series of glass jars were added 90 pbw isooctyl acrylate (hereinafter "IOA", prepared according to methods known in the art), 10 pbw acrylic acid (hereinafter "AA"), 0.04 parts per hundred (pph) 2,2-dimethoxy-2-phenyl-1-pl,.",~' ' (Ciba-Geigy), and varying amounts of ~lYIu~r~ -r (hereinafter "ABP", made according to procedures known in the literature). Each jar was purged with nitrogen and the contents exposed to low intensity W
radiation so as to partially polymerize the monomers and form coatable mixtures ~I.e., ~ having viscosities of about 3000 cP). An additional 0.16 pph 2,2-dimethoxy-2-phenyl~ ,,La.~ , and varying amounts of 1,6-hexa-..,,hyl. .li.,l. i -- .. ~ (hereinafter "HDDA") were then added to each mixture Each mixture was coated on y~ h~ h~e-coated silicone-treated paper release liner (cu.. ,.~,h~ available firom a variety of sources) at a thickness of 1~ 0.13 mm. Wl~ile the oxygen level of the curing chamber was maintained at 250 20 ppm, each coated mixture was then exposed to low intensity radiation for about 145 seconds, the first one-tbird of that time at an intensity of 1.9 mW/cm2 (measured in accordance with the previously described NIST standards) and the remainder of that time at an intensity of 4.2 mW/cm2. Some of the coated rnixtures were also exposed for about five seconds to bigh intensity radiation, which had an average intensity of 112 mW/cm2.

wo 96105249 r~ 2 ~ 9 6 i 7 3 P~

Table II: ABP
Shear Strength (min) l~xample Amt. Amt.High intensity RT 70~C Peel No. A13P HDDAradiation? strength (pph) (pph) (N/dm) Cl 0 0.1 No 10,000+ 158 170 C2 0.2 0 No 6 4 88 0.2 0.05 No 10,000+ 10,000+ 230 2 0.3 0.05 No 10,000+ 10,000+ 230 3 0.045 0.05 No 5110 116 210 C3 0 0.1 Yes 10,000+ 141 200 C4 0.1 0 Yes 830 21 190 4 0.25 0.05 Yes 10,000+ 10,000+ 180 0.126 0.05 Yes 10,000+ 10,000+ 190 6 0.0075 0.05 Yes 10,000+ 512 210 7 0.025 0 Yes 10,000+ 10,000+ 160 When oniy HDDA or ABP ~ is used aiong with oniy low 5 intensity radiation (Examples Cl and C2), one does not obtain a PSA with high shear strengths at both ambient and elevated i , .,~ as well as high peel strength. When ABP and HDDA are used in ' ~ with oniy low intensity radiation (Examples I and 2), one does obtain a PSA with baianced properties.
Example 3 shows that, where high intensity radiation is not used, low levels of o ABP are not preferred if a PSA with high shear strength is desired.
When oniy HDDA or a small amount (e.g., up to about 0.1 pph) of ABP
illd;~ is used aiong with both low and high intensity radiation (Examples C3and C4), one still does not obtain a PSA with balanced properties. However, one does obtain a PSA with baianced properties when ~iDDA and ABP are used in 15 ~.~.. j. . 6. " . along with a e~ ;. . of low and high intensity radiation (Examples 4 and 5) uniess too smail of an amount of ABP is used (Example 6).
When a moderate amount of ABP is used along with both low and high intensity w0 96/0s249 ~ 9 6 1 7 3 ~

radiation, a PSA with good shear properties can be obtained, aithough such a PSAhas a lower peel strength than a similar PSA containing FiDDA (Example 7).
Therefore, using ABP in, ' with a pul~u~ u~t~,d monomer such as HDDA is generaily preferred.
Examples 8-15: Au.~' ~ ' L ,' To a 250 mL round bottom flask were added 6.95 g (0.05 mole) 2-vinyl-4,4- " ' ,h ' - - (SNPE, Inc.; Princeton, NJ), 9.90 g (0.05 mole) 4-hydroxy-b. .~.1.. . (Aidrich Chemicai Co.; Milwaukee, Wl), and 50 mL ethyi acetate.
This solution was ~ stirred at room l~,~lly~,~al~llc; while 0.38 g (0.00025 mole) 1,8-~1 - 1. ~.,L~[5.4.0]undec-7-ene (Aidrich Chemicai Co.) was added.
The solution ;ll....~,li~.~.,l~ turned yellow and, within 30 minutes, an insoluble powdery white solid formed. This solid was collected by fiitration, washed with cold ethyl acetate, and dried in vacuo. A totai of 12.45 g was collected (74%
yield), a sample of which was found to have a melting point of 131 -131.5~C. IR
and N~ ~ 1- U;~U~ was used to identify the product as 4-[2-(N-propenoyl)amino-2 ' J!".~, "lu,.~ , cailed aul)~ldulllulJ~ -r or"AcBPnbelow.
To a series of glass jars were added 90 pbw IOA, 10 pbw AA, 0.04 pph 2,2-dimethoxy-2-phenyl-1-1,h_.,J: ' ~, and varying amounts of the above-described AcBP. Each jar was purged with nitrogen and the contents exposed to low intensity W radiation so as to partially polymerize the monomers and form coatable mixtures. An additionai 0.10 pph 2,2-dimethoxy-2-phenyl-1-ph~,llJ~ ~ was then added to each mixture.
Each mixture was coated on pGl~.,lh~k,.. ~,-coated siiicone-treated paper release liner at a thickness of 0.13 mm. While the oxygen level of the curing chamber was maintained at 220 l 20 ppm, each coated mixture was then exposed to low intensity radiation for about 105 seconds at an average intensity of 4.6 mW/cm2 Some of the coated mixtures were also exposed to high intensity 30 radiation until an additionai 347 mJ/cm2 of energy had been applied.

wos6/0s24sS ~ ~ t 5 2 1 96 t 73 1~ .2 Table III: AcBP
AcBP (pph) Shear Strength (min) Ex. No Added to AddedHigh intensity RT 70~C Peel monomers to syrup radiation? strength (N/dm) 8 0.1 0 No 54 2 159 9 0.3 0 No 111 9 157 0 0.1 No 109 9 147 I l 0 0.3 No 159 12 170 12 0.1 0 Yes 10,000+ 2418- 129 13 0.3 0 Yes 10,000+ 10,000+ 149 14 0 0.1 Yes 10,000+ 10,000+ 160 0 0.3 Yes 10,000+ 2888' 155 'Pop-offfailure.

s The data of Table III show that AcBP-containing PSAs with high shear values can be prepared only when high intensity radiation is used in ~.... ,l . - ~ ;. ,.~
with low intensity radiation. PSAs with balanced properties can be obtained using a relatively large amount of AcBP in the initial monomer mixture or by adding a relatively small amount of AcBP to an already-made syrup. A pol~, lo monomer such as HDDA need not be included to obtain a PSA with balanced properties.
Examples 16-24: Al,l~'.. Ie~ . ' in a tackified acrylate To a series of glass jars were added 8 I pbw IOA, I .5 pbw AA, 18.5 pbw isobornyl acrylate (hereinafter "IBA"), 0.04 pph 2,2-dimethoxy-2-phenyl-1-pll.,..~' ' , and varying amounts of AcBP. Each jar was purged with nitrogen and the contents exposed to low intensity W radiation so as to partially polymerize the monomers and form coatable mixtures. An additional 0.20 pph 2,2-dimethoxy-2-phenyl-1-pl..,..J' ' , varying amounts of HDDA, and w096/05249 ~. ~; t ~ S 26 2 ~ 9~ ~ 73 r~ S

varying amounts of RegalrezTM 6108 tacicifier (Hercules Co.; W;ll. ..O.uu, DE) were then added to each mixture.
Each mixture was coated on pol~,LhJh,...,-coated siiicone-treated paper release iiner at a thicicness of 0.13 mm. While the oxygen level of the curing 5 chamber was maintained at I 00 + 20 ppm, each coated mixture was then exposed to low intensity radiation for about 100 seconds at an average intensity of 4.8 mW/cm2. The coated mixtures were also exposed to high intensity radiation (i.e.,71 mW/cm2) for 12 seconds.
In addition to peel tests on stainless steel, peel tests on pcl~Jlu~ ,.le o ("PP") substrates were also performed. (The same procedure was used to adhere samples to stainiess steel was used to adhere samples to pol~n~""h,~.). Each pG~ ,l.., substrate was cleaned three times with heptane before application of adhesive. Additionally, only a twenty minute dwell time was observed before testing Table IV
Shear Strength (nun) Peel Strength (N/drn) Exarnple AcBP i'lDDA Tackifier RT 70~C St. PP
No. (pph)(pph) (pph) steel 16 0.10 0 20 18 1 73.6 76.4 17 o.lO 0.04 20 54 3 66.5 72.9 18 0.10 0.12 20 3412 381 65.1 78.1 19 0.16 0 20 34 1 68.3 98.4 0.16 0.04 20 146 7 67.9 103 21 0.16 0.12 20 lo,ooo+ 10,000+ 77.1 92.5 22 0.16 0 30 55 1 69.4 81.6 23 0.16 0.04 30 1983 137 78.1 82.3 24 0.16 0.12 30 lo,OOO+ lo,ooo+ 71.5 75.0 The data of Table IV show that, in systems containing tacicif ers, higher levels of AcBP and ED~DA are required to obtain high static shear values.

W0 96/05249 ~ t S 2 ~ 9 6 1 7 3 Examples 25-28: Aw~' ' ' r in .
with a ~. r '' ~ acrylate To a series of glass jars were added 90 pbw IOA, 10 pbw AA, 0.04 pph 5 2,2-dimethoxy-2-phenyl-1-l ' J' -'' , 15 pph KE 311TM tackifier (Arakawa Chemical Co.; Chicago, lL), 0.05 pph HDDA, and varying amounts of AcBP.
Each jar was purged with nitrogen and the contents exposed to low intensity W
radiation so as to partially polymerize the monomers and form coatable mixtures.An additional 0.16 pph 2,2-dimethoxy-2-phenyl-1-pl.~,..Jk,llla.,o..e and varyingo amounts of HDDA were added to each mixture.
Each mixture was coated on pul~,,llyL,..~,-coated silicone treated paper release liner at a thickness of 0.13 mm while the oxygen level of the curing chamber was maintained at about 100 ppm, each coated mixture was exposed to low intensity radiation for about 105 seconds at an average intensity of 4.6 mW/cm2. An 843 mJ/cm2 high intensity exposure at an average intensity of 102 mW/cm2 was thereafter applied.
The test procedures were the same as described above with the exception that the stainless steel peel test were performed 20 minutes after the adhesive films were applied to the substrates.
Table V: AcBP and HDDA
HDDA, added Stainless Shear Values(min) AcBPto syrup Steel Peel Sample (pph) (N/dm) RT 70~C
0.10 0.05 75.7 10,000+ 10,000+
26 0.10 0.10 76.7 10,000+ 10,000+
27 0.40 0.05 86.2 5490' 10,000+
28 0.40 0.10 80.2 10,000+ 10,000+

'Pop-offfailure.

wo 96/0s249 ~ 3 t t~
~r ~ 2196173 ~

Examples 29-48 To a series of glass jars were added 90 pbw IOA, 10 pbw AA, and 0.04 pph 2,2-dimethoxy-2-phenyl- 1 -PI~ .J ' hl Various amounts of the C
monomers shown below were added to some of the jars.

CH2=C--C--NH~?OCH2~

R ~ H in Examples 29-38 CH3 in Examples 39-48 5 (In other of the jars, the C monomer was not added until after the contents of the jar had been partially pGi~ ' ' SO as to provide a syrup.) Each jar was purged with nitrogen and the contents exposed to low intensity W radiation so as to partially polymerize the monomers and form coatable mixtures. To each mixture was added an additional 0.12 pph 2,2-dimethoxy-2-phenyl-1-l ' ,' ' , 0.05 0 pph HDDA, and, to the jars to which no C monomer had previously been added, varying amounts of C monomer.
Each mixture was coated on pGl ~ ,..e-coated silicone treated paper release liner at a thickness of 0.13 mm while the oxygen level of the curing chamber was maintained at about 250 ppm, each coated mixture was exposed to low intensity radiation for about 100 seconds at an average intensity of 2.0 mW/cm2. Both shear strength and peel strength ~ , were then taken.
A 280 mJ/cm2 high intensity exposure at an average intensity of 18 mW/cm2 was thereafter applied and the peel strength values were again measured.
The test procedures were the same as described above with the exception 20 that the stainless steel peel test were performed 20 minutes after the adhesive films were applied to the substrates.

W0 96105249 ~ 2 ~ 96 ~ 73 Table Vl Ex. No. C monomer (pbw) Shear Strength (min) Peel Strength (N/dm) Added to Lhe Added to the RT 70~CLow illt. rad. Lvw and high monomer Sylup oDly illLrad.
mixture 29 0.0075 - 4571 48 139 146 30 0.05 - 10,000+ 524 139 123 31 0.10 - 10,000+ 10,000+ 132 129 32 0.15 - 10,000+ 10,000+ 101 109 33 0.20 - 10,000+ 10,000+ 103 90 34 - 0.0075 10,000+ 1~7 147 167 - 0.05 10,000+ 156 143 161 36 - 0.10 10,000+ 117 134 150 37 - 0.15 10,000+ 124 142 156 38 - 0.20 10,000+ 395 IZ7 135 390.0075 - 10,000+ 66 127 149 40 0.05 - 10,000+ 10,000+ 137 151 41 0.10 - 10,000+ 10,000+ 126 119 42 0.15 - 10,000+ 10,000+ 110 103 43 0.20 - 10,000+ 10,000+ 81 80 44 - 0.0075 10,000+ 95 156 157 - 0.05 10,000+ 127 152 156 46 - 0.10 10,000+ 305 144 151 47 - 0.15 10,000+ 106 124 127 48 - 0.20 10,000+ 100 132 140 The data of Table VI show that adhesives with better high L.,.~.~J.,. dtl~
shear values are obtained when eLhy~ " ' monomer comprising a 5 radiation-sensitive hydrogen abstracting group (i.e., a C monomer) is added to the monomer mixture rather than to the syrup. N.,~,. Ihel~ , adhesives with good low ttlll~ lul l; shear values can be obtained when C monomer is added to the SylUp.

wo 96/05249 ,~ p ~ 2 1 9 6 1 7 3 P~ ,2 Examples 49-60: Thermal initiation Into a glass bottle were charged 90 g IOA, 10 g AA, 5 g 2,2'-aZObis(isUl~-lLy~u~ I,Umll...e;~ available as VAZO 64~M free radical initiator (DuPont; ~ u.., DE). The bottle was purged with nitrogen and 5 sealed before being placed in a 60~C bath and tumbled for 24 hours. A
~,u---~ L;ve (i.e., control) sy~up having an inherent viscosity of 0. 82 dUgm was recovered.
Syrups that included l,upul~ of IOA, AA and various C monomers were prepared as above. Each ofthese SylUpS was coated onto 37 llm polyester 0 substrates to provide dry coating thicknesses of 50 llm. The coated films werecured to PSAs by exposure to a~ u~dll-dl.,ly 200 mJ from one of three tyypes of bulbs: "H bulb" (200 - 350 nm), "Q bulb" (330 - 450 nm), or "V bulb" (350 - 470 nm).
The PSA samples were tested under constant LL,..~ Lul ~; and humidity.
15 Shear strength tests were performed as described previously. Peel strength tests were performed at 180~ using a tester speed of 30.5 cm/min. The results are shown below in Table VII.

wos6/0s249 ~ t ~ 2 ~ 96 ~ 73 r~"~

Table VII
Shear Strength (min) Ex. No. C monomer Bulb RT 70~C 180~Peel Strength(N/dm) 49 a H 10,000+ 10,000+ 31.5 r 50 a Q 10,000+ 10,000+ 21.2 51 a V 10,000+ 10,000+ 18.2 52 b H 10,000+ 10,000+ 9.5 53 b Q 10,000+ 10,000+ 33.8 54 b V 10,000+ 10,000+ 18.5 c H 10,000+ 10,000+ 27.0 56 c Q 10,000+ 10,000+ 35.7 57 c V 10,000+ 10,000+ 26.4 58 d H 10,000+ 10,000+ 27.9 59 d Q 10,000+ 10,000+ 8.2 d V 10,000+ 10,000+ 22.7 a=ABP
b = AcBP
c = C monomer from Examples 29-38 d = C monomer from Examples 3948 (Tapes with adhesive thicknesses of 125 llm gave shear strengths similar to those o shown in Table V.iI.) The data of Table VII show that PSAs made from syrups in which the polymer was prepared in sitt/ by thermal initiation have excellent shear properties at both ambient and elevated Ltlll,~ LI.. ~

Example 61:
3-[2-(N-2-propenyl)amino-2- ' ~IplulJalluylu~ ]~ . (AcAc) A mixture of 27.2 g (0.20 mol) 3 Lydlu~a~ , ' . (Aidrich Chemicai Co.), 27.8 g (0.20 mol) ..;..~ld;.~."Lllyl aziactone (SNPE, Inc.), and 0.50 g (3.3 20 mmol) DBU was heated at 90~C for 18 hours. The product was ~

wo 96/05249 .- ~ l;,, p 1 ~ 2 1 9 6 1 7 3 I ~ I l u ,,. ~

from aqueous ethanol to afford 30.7 g (55~/0) of the acrylarnide as a white solid, with a melting point of 115-117~C. IR and NMR spectra were consistent with those expected for the desired product.

Examples 62-67: Testing of AcAc To a series of glass jars were added 90 pbw IOA, 10 pbw AA, and 0.04 pph 2,2-dimethoxy-2-phenyl-1-l ' ~' ' (Ciba-Geigy Corp.; Ardsley, NY).
To some of the jars were added varying amounts of AcAc. To other of the jars, ABP or AcBP was not added until after the contents of the jar had been partiallypGI,~ SO as to provide a syrup. Each jar was purged with nitrogen and the contents exposed to low intensity W radiation so as to partially polymerize the monomers and form coatable mixtures. To each mixture was added an additional 0.12 pph 2,2-dimethoxy-2-phenyl-1-~,h~,..~' ' Each mixture was coated and pul~ d as in Examples 8-15.

w096/0s249 2 t 9S 1 73 r~ 2 Table vm Example No. AcAc (pbw) Shear Strength (min) Added toAdded to the RT 70~C
monomers syrup 62 0.1 - 1105 25 63 0.3 --- 1948 34 64 0.5 --- 2595 49 --- 0.1 4129 90 66 --- 0.3 1883 105 67 --- 0.5 IOK + 4162 Various .. ,. ~ and alterations that do not depart from the scope and spirit of this invention will become apparent to those skilled in the art. This 5 invention is not to be unduly limited to the illustrative e ~ " set forth herein.

Claims (13)

We claim:

1. A syrup curable to a crosslinked viscoelastomeric material comprising:
a) about 65 to 99.9 weight percent of a solvent monomer mixture comprising 1) 95 to 99.9999 parts by weight of at least one free radically-polymerizable ethylenically monomer, and 2) 0.0001 to 5 parts by weight of an ethylenically unsaturated monomer comprising a radiation-sensitive hydrogen abstracting group;
b) about 0.1 to 35 weight percent of a solute polymer comprising 1) 95 to 99.9999 weight percent mer units derived from one or more free radically-polymerizable ethylenically unsaturated monomers, and 2) about 0.001 to 5 weight percent mer units derived from an ethylenically unsaturated monomer comprising a radiation-sensitive hydrogen abstracting group, said polymer having a molecular weight of at least 500,000;
c) from 0 to 5 parts by weight of a free radically-polymerizable polyethylenically unsaturated monomer; and d) from 0.0001 to 3 parts by weight of a saturated energy-activated initiator of polymerization.

2. The syrup of claim 1 wherein said at least one free radically-polymerizable ethylenically unsaturated monomer of said monomer mixture comprises a monoethylenically unsaturated monomer homopolymerizable to a polymer having a glass transition temperature of less than about 0°C.

3. The syrup of claim 2 wherein said at least one free radically-polymerizable ethylenically unsaturated monomer is selected from the group consisting of isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, decylacrylate, dodecyl acrylate, hexyl acrylate, and butyl acrylate.

4. The syrup of claim 2 wherein said at least one free radically-polymerizable ethylenically unsaturated monomer further comprises a monoethylenically unsaturated monomer homopolymerizable to a polymer having a glass transition temperature of greater than about 50°C.

5. The syrup of claim 4 wherein said second monoethylenically unsaturated monomer is selected from the group consisting of (meth)acrylic acid,itaconic acid, N,N-dimethylacrylamide, N-octylacrylamide, 2-hydroxyethyl acrylate, N-vinyl pyrrolidone, N-vinyl caprolactam, acrylonitrile, tetrahydrofurfuryl acrylate, and isobornyl acrylate.

6. The syrup of claim 1 wherein said ethylenically unsaturated monomer comprising a radiation sensitive group has the formula wherein R is H or a C1 to C3 alkyl group, preferably H or a methyl group;
X is O or NH;
n is 0 or 1 ;
m is 0 or an integer from 1 to 5;
a,b,and c are independently 0 or 1;
M1 is CH2 or SiR1R2;
M2 is CR3R4 or SiR1R2;
M3 is O, NH, C(O), C(O)O, C(O)NH, or OC(O)NH;
R1 and R2 are independently H or a C1 to C4 alkyl group;

R3 and R4 are independently H, an alkyl group having 1 to 14 carbon atoms, a cycloalkyl group having 3 to 14 carbon atoms, an aryl group having 5 to 12 ring atoms, an arenyl group having 6 to 26 carbon and 0 to 3 S, N, and nonperoxidic O heteroatoms, or R3 and R4 taken together with the carbon to which they are attached form a carbocyclic ring containing 4 to 12 ring atoms;
G is a covalent bond, (CH2)d, or (CH2)dO where d is an integer from 1 to 4, preferably from 1 to 2;
Z is a radiation-sensitive hydrogen abstracting group having the general formula in which Ar is a substituted arene having 6 to 12 carbon atoms, preferably a benzenetriyl group;
R5 is hydrogen, a C1 to C12 alkyl group, a C1 to C12 alkoxy group, or a phenyl group; and R6 is a C1 to C6 alkyl group, a cycloalkyl group having 3 to 14 carbon atoms, or wherein R7 and R8 are independently selected from the class consisting of hydrogen, C1 to C12 alkyl groups, C1 to C12 alkoxy groups, and phenyl groups, with the proviso that, when R5 and R7 (or R8) are ortho to the carbonyl group ofZ, together they can be one of , , and .

7. The syrup of claim 1 wherein said syrup comprises 0.001 to 1.0 parts by weight of said saturated energy-activated initiator of polymerization.

8. The syrup of claim 7 wherein said energy is ultraviolet radiation.

9. The syrup of claim 7 wherein said monomer mixture comprises from 0.005 to 3 parts by weight of said ethylenically unsaturated monomer comprising a radiation-sensitive hydrogen abstracting group.

10. The syrup of claim 1 wherein said syrup comprises from 0.01 to 0.30 parts by weight of said free radically-polymerizable polyethylenically unsaturated monomer.

11. The syrup of claim 1 wherein said syrup is of a coatable viscosity.

12. A process for making a crosslinked viscoelastomeric material comprising the steps:
a) providing a composition comprising 1) a solvent monomer mixture comprising (a) at least one free radically-polymerizable ethylenically unsaturated monomer, and (b) 0.0001 to 5 parts by weight of an ethylenically unsaturated monomer comprising a radiation-sensitive hydrogen abstracting group, and 2) 0.0001 to 3 parts by weight of a saturated energy-activated initiator of polymerization;
b) exposing said composition to energy so as to partially polymerize said monomer mixture to form a coatable syrup;
c) adding to said syrup, based on the total amount of monomer initially present in said monomer mixture, 1) 0 to 3 parts by weight of a saturated energy-activated initiator of polymerization, 2) 0 to 3 parts by weight of an ethylenically unsaturated monomer comprising a radiation-sensitive hydrogen abstracting group, and 3) 0 to 5 parts by weight of a free radically-polymerizable polyethylenically monomer; and d) exposing said syrup to energy that activates said initiator and said hydrogen abstracting group of said ethylenically unsaturated monomer comprising a radiation-sensitive hydrogen abstracting group so as to form said crosslinked viscoelastomeric material.

13. The process of claim 12 wherein said ethylenically unsaturated monomer comprising a radiation-sensitive hydrogen abstracting group has the formula wherein R is H or a C1 to C3 alkyl group, preferably H or a methyl group;
X is O or NH;
n is 0 or 1;
m is 0 or an integer from 1 to 5;
a,b,and c are independently 0 or 1;
M1 is CH2 or SiR1R2;
M2 is CR3R4 or SiR1R2;
M3 is O, NH, C(O), C(O)O, C(O)NH, or OC(O)NH;
R1 and R2 are independently H or a C1 to C4 alkyl group;

R3 and R4 are independently H, an alkyl group having 1 to 14 carbon atoms, a cycloalkyl group having 3 to 14 carbon atoms, an aryl group having 5 to 12 ring atoms, an arenyl group having 6 to 26 carbon and 0 to 3 S, N, and nonperoxidic O heteroatoms, or R3 and R4 taken together with the carbon to which they are attached form a carbocyclic ring containing 4 to 12 ring atoms;
G is a covalent bond, (CH2)d, or (CH2)dO where d is an integer from 1 to 4, preferably from 1 to 2;
Z is a radiation-sensitive hydrogen abstracting group having the general formula in which Ar is a substituted arene group having 6 to 12 carbon atoms;
R5 is hydrogen, a C1 to C12 alkyl group, a C1 to C12 alkoxy group, or a phenyl group; and R6 is a C1 to C6 alkyl group, a cycloalkyl group having 3 to 14 carbon atoms, or wherein R7 and R8 are independently selected from the class consisting of hydrogen, C1 to C12 alkyl groups, C1 to C12 alkoxy groups, and phenyl groups, with the proviso that, when R5 and R7 (or R8) are ortho to the carbonyl group ofZ, together they can be one of , , and .