CA2129730C

CA2129730C - Radiation crosslinked elastomers

Info

Publication number: CA2129730C
Application number: CA002129730A
Authority: CA
Inventors: Albert I. Everaerts; Audrey A. Sherman; Charles M. Leir
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1992-02-10
Filing date: 1992-12-11
Publication date: 1998-07-14
Anticipated expiration: 2012-12-11
Also published as: BR9207079A; DE69211360D1; WO1993016131A1; AU3245893A; JPH07504926A; AU673342B2; EP0625998A1; EP0625998B1; KR950700352A; CA2129730A1; JP3174337B2; US5407971A; DE69211360T2

Abstract

Disclosed are radiation-crosslinkable elastomeric compositions containing: (a) a n elastomeric polymer containing abstractable hydrogen atoms in an amount sufficient to enable the elastomeric po lymer to undergo crosslinking in the presence of a suitable radiation-activatable crosslinking agent; and (b) a radiation-activatab le crosslinking agent of formula (1), wherein: W represents -O-, -N-, or -S-; X represents CH3- or (2), Y represents a ketone, es ter, or amide functionality; Z represents on organic spacer which does not contain hydrogen atoms that are more photoabstract able than hydrogen atoms of the elastomeric polymer; m represents an integer of 0 to 6; a represents 0 or 1; and n represents an integer of 2 or greater. Radiation-crosslinked elastomers are prepared by exposing the radiation-crosslin kable elastomeric compositions to radiation (e.g., UV light) to abstract hydrogen atoms from the elastomeric polymer by the resulting radiation-activated crosslinking agent.

Description

W~O 93/16131 2 ~ 2 9 l ~ ~ PCI~/US92/10637 RADIATION CRO~C~-~KED ELASTOMERS

pll;.~ OF ~l H ~ ~vR~TIoN
- s This inventi~ rela2es to radia~on~r~sslin~able e~ o-~r,~;c eo~s;~ s which employ a .~ ~tivatable c,~o~rli~i~ agent. This i"~/~..tion also relates ~adiadon cros~ d ehstomeric compositions.

~CK~ROU~l~ OF TPP. ~VP~IION
lo It is known that ~wslin~ing of polymers produces polymer networlcs which have qui2e different mechanical and physical prop~s compared to their uncwssli~ed linear or branched countapcu2s. For e3~ample, polymer networks can show such unique and highly desirablc p~ s as solvent re~s~nce, high cohesi~c strength, and elas20mcnc cha~acter.
~5 Cros~ ked polymers can be madc j~ dunng formation of thc dcsired polymcr product, however, since furthcr p~og of ~e polymcr product is ~f~n nc~~, it is morc typical ~ start from ~c linear or branch d polymer which in ~e final p~ing step is curcd to a ~wli~d matuial. Thc curing or cmsslin~ng stcp is typically a~vated by moisture, thcrmal energy, or radiation. Ibc htter has found w;d~l~d applications, par2icularly in the use of ultraviolet light as the radiation sourcc.
In the past, a variety of differcnt mater~als have boen used as crosslinlcing agents, e.g. pclyr;~ t;o~~l acrylates, acetophr~ n~s, benzophenones, and tna~nes.
The forcgoing clvssliDldng agents, however, ~05:~-C~ certain d~awbacks which i~ de one or more of the following: high volatility; inrA~ uy~t;hility with certain p~lynlc~
S~ S, g~&-~;on of corrosive or to~cic by-pl~lucls, gene~ation of ~d~able color; ~ui~ cn~ of a separate ~kot~ e co~ l to initiate the c~os~linlring ;Qn; and _igh sensitivity to o~tygen.
Certain pol~.~nc~ n~l bcn~ h~ n~s have been inv~~ti~ted as photocl~s~l.nki~g agents andlor ~oto~n~ in vanous pho~opol~ bl~
systems.

WO 93/16131 ~,~ 9 ~1 ~J ~ Pcr/uss2~lo637 JP 54/057560 ~ oses the use of (bis)be ~zophenone compounds to phOtOCr~SSlillk non-elastol-lc.ic m~ ri~ - in particular, polyester co.~ oC;t;onc.
When incol~lated into pol,~st~, they impart improved tensile ~ englll and elo~g~tion to bia~cally s~,tcl~d films of cr~s~linlr~ poly(ethylene t~
These films also exhibit en'~nc~ alhe., heat, and ~hP-.. ;r~l rÇcict~ne~ and improved ~1i,,,r...c:on~1 stability.
U.S. Pat. No. 4,602~097 (Curtis) di~lo~s the use of (bis)~ 7~henonp~s as ..kot~in~ t~s and/or ~ot~s~ s in r~ tion cured coatings. The poly(ethylene oxide) moiety ~Ybieh sep~ s the t~ b~ o~e~o~P groups allows ~e c~ d cc--~s;lions to be more soluble than unsubstitut~ed b~ rs in wate~b~.ne coating compositions. The (bis)ben-Qph~ o~e eompounds, however, eontain h~d~,en donating groups, such as the me~ s adjacent to the o~cygen atoms of the ether funetionalities. These hydrogen donating groups undergo an intramolecular hydr~6~,~ abstraction by the phot~ehemically eaccited (~ ophenone s~uch~e to ~.idc a lower energy radical whieh is ~îf~ as an ini~ator, but unsuitable as a pho~inl~.
U.S. Pat. No. 4,379,201 ~Heilmann et al.) is an a~ample ~f a elass of polyacrglic-r~ tinu~l crossli~s used in the photocuring of (meLb)acrylate ners. U.S. Pat. Nos. 4,391,678 (Ves~ey) and 4,330,590 (Vcsley) describe a ~ class o~ fast curing tna~ne photo~wslink~rs which, whcn mi~ced with an acrylic~nn~n~(or and, optionally, a n.<~ h~ nically unsah~ated monomer, and ~ d to W ~ation, forms a c~os~lin~ p~ la~. The crosslinlcs fwrn~ by both the (meth)d~ tes and the ~ s in these Copc~ly~ ;o~c prevent any further sc;ne~suchashotmelt C4~i~, reactive~~ n~ors~ut;n-~ ;n~p~oC~C
following the initial pho~ ;on.
U.S. Pat. No. 4,737,559 (Kellen et al.) ~;SflO~ES acl~l~te-r~ ;nn~l aro,..atic k~lones (~n par~eular, 4-acrylc,Ay~~ hF-n~ r- (ABP)) which are ~ ~ with other (meth)acl~late ~ nc--e-~ to fonn p~ u~-sens;li~e adhesive COp~
~onl~ini~g pe .d;~nt ben7opl~enc~ne groups. These bel~>~ph~"nG rnnc.1;~n~ .cs .~ ~-sensitive adhesive copol~n.c~s uAd~o effi~iPnt c~sS~ i~ upon e-l~surc to W
light, esp~iqlly when CO~ d tO the use of conventional b~ ~c.~h~none as a pho~ u~cl;nl~pr~ This patent also ~l~c;fie~lly states that the ~;C~'lQ~l CO..~l ou"ds wo 93/16131 2 1 2 9 7 ~; ~ pcr/usg2/lo637 must be free of hyd~ y groups in a positi~n ortho t~ the c~l,onyl fi~nGti~nqlity.
These hyd~ s~l~5~ ent~ inhibit free radical fo~q~ and hyd.~2en ~s~
from the acrylate cop~l~mer ~-LI~one. However, since these acrylate-r-~ct;~ q1 aromatic ketones are monomers to be copol~.- e-;~d y~;1y with other acrylic S ~- C~Q ~ , they are not useful as a post-~ e ;~ -~;Qn p~-o~sslinker which may - beco~ oL~d~dwith p~ iOL~ ,~lodel~t~ ;G~~ of ~ ,gc character.
A suitable class of ~= ~=~a e ~1Y~L--C~ acetoph~o~c and be~o~h~one crosslinking agents for elastomers has not been ~cognized or utilized10to date and has been hcking in ~e industry. It was against this bacl~round tbat a scarch for such a suitable class of Ddiation-activatable polyfi~onal aoetophenone and benzo~henone erosslinl~ng agents for ehstomers was conductod.

~U~MARy OF TPP- ~VI~TION
15In one embo~t of the p~esent inventio~ thae is pro~nded a ~adia~oD-crosslin~ble composition eompnsing: (a) an dastDmenc polymer cont~ning abs~le hydrogen atoms in an amount suf~icient tD alable ~e daston~c polymer to undergo clossli~ng in thc presence of a suit~blc ~dia~on-acti~ahblc cmsslin}ing agent; and ~b) a radia~on~vatablc closslin~ng agent of thc form~a:

o ~--c~ a 2, a - - n wherein:
W .~,~,~nts -~,-N-, or -S-, X r~ ~nts CH3- or wo 93/16131 ~ Pcr/uss2/l0637 Y ~~wents a ketone, ester, or amide f inc';o~ ity;
Z ~cp~cscnts a pol~r..~ n~l o.~Sanic segment which does not contain hydrogen atoms that are more photoa~sn~ than h~,d~g,cn atoms of the el~c~ polymer;
m ~.~nls an integer of from 0 to 6;
a ~nls 0 or 1; and n n~ ts an integer of 2 or greater.
In anotner embo~ of the present ~C~t;OI~ there is p ~.id~ a radiation crosslinked composidon p~epared by the pl.~cess of subjecdng the above-disclosed crosslinhble composition to ~adiation under co~d;~ c syrr~ t to ~o abst~t hydrogen atoms from the dastomuic polymer by the ~diation-activatcd crosslinl~ng agent disclosed earlicr herein.
So far as is Icnown, no one has prc~iously u~lized any of thc above!disclosed ~adiation-activatable polyfunctional aceloph~ones and bel~zophenones as c~liD~ngagcnts for elastomedc polymcrs. Addi~onally, the usc of the above!discloscd polyfunctional acctophcnones and b~he~ones affo~ds a number of advantages as - compared to the use of conven'donal cn~sslin~ing agents for dastomers. These advantages include, but are not limited toj lowaed vo~a~lity of the ~osslin~ng agent duc to its higher ~lecular weight; incra~sed compatibility of the ~ ~s~ pr through thc selec~ion of pol~al orgaluc segment; d~o~d sensitivib of thc c~ssliJ;~ble composition to ~~6--1; the avoidance of cvolution of any twcic or co~rosive b, p~oducts or discolo~ation of thc final product; and the c;~abiliq to be used as a post-cunng ~ios~l~ing additivc.
Oth~ ~q~, ad~rantagcs, and bcncfi1~ of the present invention are apparent f~om the de~qihd d~,fi~ir~, the acamplcs, and the claims.
Dp~rAn ~n nF~CI2lPIlON OP T~ !~ TION
The P~iq~ n~ ;n~qhle compositions used in the p.~t invention are el_C~ m~s ("~ o~ ~F :>~) which contain absha~table h~o~,en atoms. The q,~s~ le hy~ioge~ atoms will be present in the ~-q-- lrhonP and/or side chains of the e1~ton~e~ in an ~ ount slrr~ nt to allow c~s~l;nking of the el~sto,-ler upon exposure of the photocrosslinl~ng agent/eJastomer ~ ule to radiation, e.g., elec~omagnetic radiation, such as ultraviolet (~UV") light. As a ge.ne~l rule, Wo 93~16131 2 1 2 9 ~ ~ ~ Pcr/uss2/10637 hydrogen atoms are most easily abstracted from tertiary carbon atoms, those on carbon atoms in a position alpha to an o~cygen or ~ geY~ atom (e.g organic ethers and tertiary amines) and those el5~o-~eYs with lc~ 1 or pe~ ,.capt~ groups In the present invention, an elastomeric p~ r or elastomer is ~ r~ ~d as being a m~clc.. lolecular material that returns rapidly to its app.o ;~
n~;ons and shape after substantial defo....ation by a weak stress and subsequentrelease of ~at stress as measured according to ASTM D 1456-86 (~Standard Test M.ll~od Por Rubber ~o~.~ longation At S~-ifie Stress~ amples of elastomers which can be used in the present invention in~ de, but are not limited to, st~butadiene rubber (SBR), styrene-isopr,ene~ ene block copolymers (SIS), styra~butadiene-styrene block copolymers (SBS), ethylene-p,~o~ dicnc monomer ~ EPDM), polyisobutyleDe, natu~al rubber, synthetic p~l~;so,~ c, acrylonitril~butadiencoopolymers, polycbloroprcnc, ethylene-~nnylace~te, silioones, and polyac,rylates. The p~ened elastomers for usc in ~e prescnt invention are polyacrylates, silicones, liquid EPDM rubber, SBS block oo~olymas, and SIS bloclc copolymers.
The ~adiation-activatable aosslin~ng agent utilized in the present invention has the follovnng fon~ula:

~
X--C~ CCX2)--CY) Z
- n W ~p~c~ls -~,-N-, or -S-, X t/,p.~iel~b CH3- or Y l.,plwel ts a ketone, ester, or amide functi~nql Z le~es~nts a~lyfu~ n~l organic segment which does not contain hydlo~en atoms that are more photoa~stl~ble than the hyd~~,c~ atoms of the c~ o ~ lyll.e., m r~ s an integer of from 0 to 6;
: S

wo 93/1613~ ' Pcr/uss2/l0637 a ~e~l~ sents O or l; and n f~ sellts an integer of 2 or greater.
The s~lthesis of particular radiation-activatable or photoc,~s~ ki-~ agents is m~J$~ in the e~camples which follow, but in g~nP-~l the ~ilus~ agents can be syl~hPci7~d acco.~i~g to ~ c well known to those skilled in the art of s~"the.~c G.E,~niC c~emictry~ e.g. Michaelad~ nn~ hydrosil~lat;on, transe~rifir~tiQr, and co~ s One preferrcd gtoup of polyfi~nctional benwphenone cloc~ i~ agents of this invention a,~ those oompounds in which W=-~, X--l~h~l, Y=ester, Z=~CH2)2 l0, m=l, a=l, and n=2, and ~esults from thc t~anseste~ification reac~onof 2 molar equivalents of e~ bcn~oylpheno~cy)acctate, (Struc~re I below) with shon chain allcylcnc diols. Anothcr prcfeIrcd group of polyfunctional b ~ A~phcnoncs of this in~cntion arc prcpared from the roaction of Structurc I with an e~ccess of cthylcnc glycol to fo~m hydro~cy-functional b~ n-oph~none (Struc~re ~ beaow). Two molcs of hydrmcy-functional b~~e thcn undergo a c~on reaction with an aliphatic, aromatic, or cycbali~c polyfunctional i~gana~, re~l~ng in prcfeIrod closslin~ng agents with urc~ane and ester functionalities in Yvhich m=l;
Y=cstcr; X=phenyl; Zz~IrCH2~C(O~NH-R-NH-C~O)~CH2CH~; W=-O-;
and R represcnts a divalcnt aliphatic, ~matic, or cycloalip. atic moiety.

c~o--C~2-C--olst . STRUCTURE I

~8~o ~}~2 C O C~z--CH2--OH

:,.~uClu~tE II

212 97 ~
~o 93/16131 Pcr/us92/lo637 P, .-.o~, organic spacer ~ P.I~t~ Z and lin~ng f~nctionqlitips Y may be p~,~e;l to enl~nc~ the comp. tibility and de~,~se the volatility of the polyfi~nctiol-ql photoc~sslinking agents in varying p~ .~ic a~atC~lls. Por example, polyfiJncti~ n~l a~ phe~-ones and ~4phf ~lOI~f s with poly~ilo~-qne spacer ~.~m~ may be s a~t~thP c;-~;l for use in the photocuring of pol~dinlelh~kilo~ e elastomers, materials in which most non-silicon containing c~sc~ ng agents are incompatible. Thiâ
in~.ul~atibility between polymer and l~ho~ us~linW~ agents leads to r~lueed c~o~ i~ eM~cy and chrity of immiscible el~ e~/closslinl~ng agent s~s~."s.
The organic spacer S~ Z may also be s~l~ to ulûd;~ the rheological and mechanical plO~ li~s of th~e radiation clos~ r~ mat~ials. A rigid spacer group will ~esult in a diffe~ent Iheology tban a flcxible spacer group. Also, the lcngth of the ~pacer g~oup may be used to control the crosslinlc density of the ne~vork. Although the s~a~ng of the aossli~ng points along the elastomer baclcbonc may not bc procisely controlled, the size and chemical na~re of the linhge may be dcte~minod using tbc closslin~ng agents disclosed heran. As the conccnt~ation of c~ i~Dg agent docleases in the photocu~able mi~re, the p~p~ s of the c~sslin~d dastomenc ~etwork beeome increa~gly dominated by the mechanical and rheological ~ s of the eJastomer.
Organic spacer Z must be froc of readily abstra~ble hydrogens, which are p~esent in such functionalities as ethas, tbiols, allylic groups, te~ amines, and the like. When such func~onalities arc praent in the spaeer, i~adiation will cause h~d~o~~ a~ o~ at sites along the spacer segment ins~ad of abstrac~ng hydrogens from the elast~meric p~ c~ b~c~l)onr- This leads to an und~
intramolecu1ar ~backbiting~ io~ which .~luccs the phO~ûs~l~n~ Crr~e~
of mulLfn e~;o~ cl~s~ ,rs which contain spacer segments with readily a~s~ dble h~ g_ns. Thus, thc organic spacer Z must not CQ'~t--~ hydYc~,PI~ atomsthat arc more photoa~s~a.,~ble ~an the hydrogen atoms of the elastomeric ~l~.~.er to bc ~ os~
~ Preferably, about 0.01 - 25 weight % pholoc~os~;nlrinp agent, and most preferably, about O.l-lO wdght %, is employed based upon the total weight of theelastomcr. In gf'n~ thc amount of phot~cl~sslinl~ng agent employed is based upontbe ease of hyd~og~n abst~a~on from the ~l~r~ p ;r ~1~ C~1 batL1~onr~ the Wo 93~16131 ~ è?~ PCr/USs2/10637 re ctivity of the r~ licqlc formed, the intensity and length of e~s.lle of the co!..pos;t;on to irrad;qtion, and the el~Q~ ..e-~'s D~ q~ weight.
Other useful ".~t.~ lC which can be optiorqlly utilized in the present inventionin~lude, but are not limited to, ~hPr~ ly e~pandaUe pO~ C~iC ~ iC105~iC~S, glassl~uc~sphe,es,filler,p;g,.. n~$, f~ ng agentc~ l;7p~rs~firele~J~ti,visccs~
~dj--sling agents, and l ~~ ;r.e~s/~ tiei7~ys which do not interfere with ~s.~in~i~
In practice, the photo~ ,~,sslin~ng agent and otha L~5l~lients are added to the elastomer, whc~ol~ thc material can be coated by methods well-hlown in the art, such as solvent coating, hot-melt coating, solventless or wate~orne coating, andc~ll~on. The coating is thcn e~cposed to ~adiation, prefaably d~.~,netic ~adiation such as UV light, under oonditions sufficient to effect crosslinl~ing of thc clastomcr.
Thcphotocrosslinlcers are prcfe ably activated with long wavdcngth ultraviolet radiation (280-400 nm). The absorption ma~umum will de~end on the molocular struc~re of the pholoaos~g agent. Due to tbe low actinction cc~ ~c ~t of bcnzophenone- and ~c d~.i.~ ~es, it is ~ef~able to use higb intensity UV ~ights for cunng. Such UV lights, including thc PPG UV processor and Fusion Systems cuuing unit, arc commu~ally available. The PPG UV p~c~ss~r is equipped witb tw~ modium prcss~c macury lamps which bave a spoc~al output belwecn 260 and 740 nm, mainly cmissions in tbe 270 to 450 nm output ~ange. Tbe lamps can bc set at *~11 powcr (300 Watts/inch) o.r half pow~ (150 Wat~/inch). The Fusion Sys~ems cwing unit uses du,~o~lcss UV lamps with power s~ttings betwecn 100 and 600 Wattslinch. A vaIiety of bulbs are available with differing ~Ct~l Ol:tpUt~ The pl~f~l~ bulbs for the photocr~ss~ i~ agents of the in~rention are the ~D~ or ~H" bulbs, both commercially available from Fusion Systems.
Tne radiation CluSS~ ked materials are useful as sealants and coa~ing materials, such as inks, adhesives, pnnting and photographic coatings, paints, ~ uctor masks, pholor~sts, and photo~clA~;fiableadhesives.

TF.~T PRO ~.P.n~:~
The following tcst procedures were used to evaluate thc p~ss~-~nhLi~e materials usod in the c~camples.

~VO 93/16131 2 1 2 ~ 7 ~ ~ PCl'/US92/10637 Peel ~dhesi~n Peel ;Itlh~ Ol~ iS the force l_lu,l~ to r~ Ove a coated fle~cible sheet ~ t~
from a test panel ,~easu~d at a ~ fic angle and rate of ~ o.al. In the c.,~,~les, this force is ~ ssed in Newtons per dc~ c ~ (N/dm) width of coated sheet. The test follows the p~ S found in ASTM D 3330-87 ("Peel A l~rsjon of F~s;.u~e Sensitive Tape at 180~ Angle). The only d~,~liol~s from the ASTM test are the s~b~t;~ of a glass plate for the steel plate called for in the test and a change in the peel rate. A glass ~est plate is washed with diacetone ~ 4hol and cleaned with an absorbing material, such as a pape~ towel. The plate is then dried and wa~ed ~rec more times with heptane. A s~ip 0.127 dm in width of the shoet coated w~th the adhesive to be tested is applied to the ho~izontal surface of the cleaned glass test platc with at least 1.27 lineal dm in firm contact. Ihree passes in each direc~on with a 2 Icg hard mbb~ roller is uscd ~ apply the s~ip. If air bubblcs are ent~apped betwecn thc test plate and thc tcst strip, thcn thc samplc is dis~d. Thc frec cnd of thc coa~od strip is doubled back nearly touching itsdf so the anglc of l~o.~l will be 180~. Inc frec ~Id is a~cbod to thc ~on test~ scalc. 'Ihe gl;lss test platc is clamped in thc jaws of a tensilc tes~ng mal:binc which is ca~ablc of moving thc platc away from thc scalc at a constant ratc of 2.3 meters pcr minutc. Thc dwell time af~r roll down is 30 seconds. The scalc reading in Newtons is reoorded as the tape is peeled from the glass surface. The data for the first 0.5 dm of the strip is disregarded and the pealt, ~alley, and average peel is ~cordcd for the rel..ail dcr of the test Stlip.

!~h~r Stren~th 2 5 The shear shcn~lh is a ~ sule of the coh~ ess or inten~l s~n th of an adhesive. It is based upon the ?~n- of forcc required to pull an a~ c s~ip from a standard flat surface in a ~ ctiol~ pa~lkl to the surface to which it has beenaff~ed with a defi--;tP p~ . It is measured in minutes roquirod to pull a standard ~ area of adhcsive coatsd sheet material from a st~inless sted test pand under stress of a constant, standard load. This test follows the y~ d~ es~ibe~l in ASTM D
3645M-88: ~Holding Power of ~ Sensitive Au,.cs~e Tapes.~

Wo 93/16131 ~ ~ 9 ~ ~3 ~ Pcr/US92~1o637 The tests were oQnduct~ on strips of coated sheet ..~ applied to a st~inlPss steel panel which was cleaned and ~ d as descnbe~l above. A 0.127 dm by 0.127 dm portion of each strip was in firm contact with the panel with one end portion of the tape being free. The panel with the coated strip ~ rd was held ina rack such that the panel formed an angle of 178~ with the ! -~n~d tape free end which was ~s;oQed by application of a force of 1000 grams applied as a hanging wdght from the free end of the coa~d strip. The 2~ less than 180~ is used to negate any peel forces, thus insuring that only the shear forces are measured, in an attempt to more accurately detennine thc holding power of the tape bdng tested. The timeclapsed for each coated film to s~paratc from the test pand was reoorded as the shear strength. The ~pe of failurc, dther ~adhcsivc~ failures whcn thc adhe~ve se~a~s cleanly from thc pand or bacldng, or ~oohesive~ failures in which the samplc adhesive lea~res residuc on both thc test p~ and bacl~ng, is G~D
A lalown amount of polymer was put in an e3ccess of toluenc and allowod to dissolve over a 48 hr period. Thc samplc was filtered and thc ~w-,.~d solid was washed a couple timcs with fresh solvent. The solid was dded and the amount recorded. The gd content was det~minod as follows:

~j~t A 100% ~
initial wdght of sample PXAMP~
25, The following non~ g ~xamples furthe~ t~ ~e present invention.

S~nthes;s of ethyl-(~b~ ghu~u.~,)a~e (p.RP~
This molecule is an important p,~ul~or for the synthesis of the multifunctional acetophenone and ben~4phr~ e clu~inlring agents ,~ in this application. The 3 0 ethyl-(4-benzoyl-phel~oAr)~~ ~te was p.~a,~ by l~n". ;-~g a ~ e of 100.0 grams (0.51 moles) 4-h~ho.~y~ )pheno~, 85.2 grams (0.51 moles) ethyl bromoacetate and 800 ml of 2-butanone (MEK) in the presence of an e~ccess of potassium carbonate (209 grams or 1.5 moles). After three hours, the carbonate was filtered off and the wog3/l6l3l 21 2 t~l 7 3 ft.l PCl'/US92/10637 MEK removed on a rotovapor. The residue was cryst~ 7~l from is~plOp~ I alcohol to yield a white, flaly p,~lucl with a sharp "-~P~ g point of 82~C. The structure was Col~rll..lP~d by NMR.

Sy.. thes;s of 1.2 e~ pediol(4~ pnBPA) Ethyl-(4-bcnz~l phcn~,) acet te was reacted with an eAcess of ethylene glycol to give a l.lol~oh~droAy functio~ql c~ --~.md used in the C~!"dC'~Q ';Ol~ reaction descdbed in this applica~on. (As such, an aliphtatic alcohol is obtained which yidds co~e~ tion p~oducts with higher stability th n the ~hP ~l;c compounds, such as 4-hJd~uAl~t~ 4p~ 0ne.) 10 grams of thc FRPA was charged to an eacccss (40 ml) of cthylene glycol, which was dried by ~emoval of a toluenc/water aL~llo~. A few drops of a 25%
solution of sodium mctbmidc in me~anol was cbargcd as a cat~yst for thc reaction.
'Ihc mucturc was h~ated for 16 bours at 120~C. ARcr co~ling to room tcmpe~ature,tbc mLlcture was pou~ed into watcr and tbc product was act~acted witb cthylace~te.
Afler d~ ovcr ~ium sull~te, the solvcnt was rcmovod to yield a ydbwisb solid, which could bc crys~allizcd from hot tolucnc. Tbc struct~c of the wbitc powdcr wa. confi~mcd by N~.

~kPQ;C of 1.4-buta~4~1~ (C~-hiQ~
- Tbc rea~on product dcscribed hcrc will be refe~red to as C4-bi~P throughout tbis application. Thc C4 refcrs to thc number of ca~bons used for thc diol.
C4-bisBP was p~ ared by m~ing 10 g~ams (0.033 moles) of the EBPA with 1.6 grams (0.017 moles) of 1,4-butanediol. Tbe mi-Ature was then stir~ed with a magnetic bar. A few drops of methanesulfonic acid were added as a catalyst and the IlliAll-~ was heated to 120~C under constant agitadon. When cooled and washed with isopropanol, a white solid was o~1~ ncd which was p~ -;r.~ by c~ystallizadon from hot toluene. NMR analysis confirmed the s~,.ct~ of the product.

S~lllhei.s of ~ h~ h~ ?krlu~nr (IJ-bisBP) A lower molecular wdght urethane bii,be~ h~n~n~ was pie~d by dissolving 3 grams (0.01 moles) of EDBPA and 1.31 g~ns (0.005 moles) WO 93/16131 -~ Pcr/us92/to637 dicycloh~ .lhane 4,4'-diisocyanate (H12-MDI) in 15 grams of a dry 50/50 solvent ~ u~ of t~lucne and 2-b~ ol-e Dibutyl tin dilaurate was used as a catalyst. The reaclioQ was .-~onilo~d by the d;s~l~pc~ ce of the acetate in GC
analysis and the isocyanate IR ab~,~ion at about 2270 cm~l. After removal of thesolvent, a clear, viscous oil was ~o~

S~..tl.~C;c of ~ Polyester b~-n~ bisBP) A 5,000 molecular weight polyester bisbenzophenone was p~p~d by dissolving 10 grams RucofleJcTM S-1014-110 (available from RUCO Polymcr Corporation) (hydro~yl number 114.3 and oquivalent weight 490.8), 1.8 grams of EDBPA, and 3.4 g~ams of H12-MDI in 80 g~ams of 80/20 solvent mi~ture of toluenel2-butanone. A few drops of dibutyl tin dilaurate w~e added and ~c mi~cture was ,~ n~ - d for dght hours. GC analysis showed no H12-MDI or monoacelate and the l~lio,~ was sto~ed. Removal of the solvent yielded a highly viscous oil.

~;~ of pn~ n~ o~n~.$ mu~
20 grams of an 8000 molea~ar weight polydimethylsilo~canc polymcr containing 4-5 mole % paldant _yl groups ~KF-2001, available from Shin-Etsu) was n~i~ced in 20 g~ams of ~ahydrofuran along witb 2.52 grams of 4-acl~lo,~ybenzophenone (ABP). 0.5 ml of triethyl~.-ine was addod as a catalyst. This was mLlced for 16 hours at room temperature while thc di~ppauance of ABP was followed. When only a ~ace of ABP was visible, the solution was s~ d of solvcnt and h;clh~l~ninc on a rotoevaporator. 21.66 grams of a thin clear oil was obtainod.
This oil was submitted for Cl3NMR and the sh~ ~ was con~ Pd It was noted that only 65% of the merca~to groups were reacted with the ABP and that 35 % of these groups we~e remaining.

Ab~
l~ou~ o.n this ar~ic~t;"" the following abbr~ialions will be used for the dir~ t ~ r~ n~s:
AA acrylic acid MBA 2-methyl butyl acrylate WO 93/16131 2 1 ~ 9 r~ ? 1 Pcr/us92/lo637 IOA is~t~l acrylate BP b~n~h~n~nt~
ABP 4-acryloxyl~nLophenone C4-bisBP l,4~butanedi[4-beluoy1phf ~ ]~t~
Clo-bisBP 1,l0~ ~it4-benzoyll~ke~ y]~qte C1O-l~e~hoxy 1,10 decanedi[4-~.,zo~1-2-bisBP mc~ .cn~l]acetate U-bisBP urethane-bisbc n7~ph~o~r PE-bisBP polyester bisbe~ ,ph~o~
DG-bisBP dic~ylcl~egl~eol (4-~ l-phenyl) di~onate TG-bisBP tctra~ lencgl~col (4-l~.~ l phenyl) PG-bisBP poly~ lcnc~ col (4-~ l ph~nyl) d;c~l,ol ate PDMS polydimethylsilmtane PDMS-multiBP PDMSmultifi~donalbe~ ph~neof8000molecularweight Kraton~ 1107 styrcne-isopre~sty~ene bloclc cop~l~.ner a~ble f~om Shell Chemical Co.
Vis~ne~c~ LM-MS low molecular weight polyisobutylene available from EJ~%on Chemical Americas Vistanc~c~ MM modium molocular wdght polyisd,~ltyl~n~ available ~om E~on Chemical Amedcas Trilene~ 65 liquid EPDM from Unil~,dl Co.

FXAMP~.P. 1 A 901l0 IOAIAA copol~.n~ was made by solu~on pol~ t;o- in 2s ~,~ , at 40% solids. The i~.e,~nt ViSCOS~lg was lll~S~ in e~ ~, and found to be 1.28 dl g-l.
0.084 wdght p~nt (1.48 % l04 moles) of C4-bisBP was d;ssol~cd in the so1util~n p~ ,..er to form a clear, hG-~oe~n~o.Js mDcture. Tbe solvent was len-~vcd and the 100% solids adhesive was hot-melt coated at 170~C on l.5 mil primed . 30 p~l~te~. Coating thicLnfss was 1.2 mils. The coatings were W cured under a PPG pr~cessor cont-;nir.e two . ~ es~c l~-~culg lamps at full sett ng. The samples were put on a carner web lUmlih~g at 75 feet per minute through the W0 93/16131 ~ S~ ~rl ~ PCr/US92/10637 non-inerted curing ch~...ber. Peel :"~hec;on and shear hol~in~ power were measured and the results are s~ ;7~d in Table l.

COMPARATIVP FX~MpT R 1 0.054 grams (2.96 x l0~ moles) b~h~ph~ one was dissolved in the same ;on used in Example l and the solvent was 1~nl~v~ to give a clear adhesive.
Tape samples were p~ ;l using the same hot-melt coating conditions as above.
The tape- test results are s., ~ d in Table l under "CQ. ~dtive #l." Ihis example clearly demonstrates the lower crosslin~ng erl;~:~ -c~ of the be1~o~ c-~o~e.
0 Although some curing takes place, thc desirable high shear holding power seen for Example l was unobtainable.

C~MP~ATIVP PXAlUlP~.F. 2 A 9011010.075 IOAIAA/ABP tapolymcr was made in clh~lacct~te at 40%
solids. The inhe~ent viscosity in cthylace~c was 1.32 dl g-l. A tapc sample for testing was prepared using ~c same metbod as in E~amplc l. The poel and shear data are summarizod in Tablc l.

C~MPAR~TIvP~ ~XAMP~.R 3 Instead of capolymcrizing ABP, 0.0~5 wcight p~nt (2.96 ~ moles) of ABP was d~lvc~ into the 90/l0 solution adhesive from E~ample l. A tape sample was prepared and the p.op~es tes~d. Results are shown in Table l.
Comparative E~amples l 3 demonstrate the need to oo~l~ .i~ the bC"'O~ ne ci~sclinl~r into the elastomeric polymer ~-tbon~ to get high cil)s~ king err.r;~.~."r.
The use of a ~~ ;r,- ~c~;o~ ~nJopk~"t c1osc~ allows the p~ep~
of a W~sc1inlr-~ le ~ , composition with simple :~Ail;~ of the lului clos~1;nl~r level to an a~eady c~;r~ c,~.

212~7'~ ~
~'~ 93/16131 PCI~/US92~10637 W curing of acrylate adhesives Peel from glass Shear FY~1e #UV ~C~.C (N/dm) ~min) 0 70.1 ~31C
62.0 2,889c 2 62.6 10,000+
3 61.1 lO,OûO+
Comp #1 1 67.2 30&
Comp #1 2 64.8 423c Comp #1 3 60.9 1,891c Comp #2 1 61.3 1,789c Comp #2 2 61.5 3,872c Comp #2 3 60.9 9,106c Comp t3 1 67.2 418c Comp #3 2 65.0 S05c Comp A 3 61.7 1,376c 20c = oohesivc failure of thc adhe~ve + = indicates that test was lermin~od at this p~int Only thc aveIage pocl from glass is given.

25,FXAMP~ 2. 3 P"~ 4 Threc different c~os~ ,.s we~e used for curing a 90/10 IOAIAA solution adhesive with 1.28 dl g-l inhcrent viscosity of E~ample 1. The ,~c~i~e c~;o~ PI~ophf-n~nP~s wcre U-bisBP for EJ~ample 2, C4~i~BP for E~cample 3, and PE-bisBP for EJcample 4. ~11 thc crosslinkers dissol~ed quitc readily in the ~ l~tc soludons to form clear, ho .. r~g.P,n~--C ll~u~es. ~e 40% solids soludons were Imife-coated onto 1.5 mil primed p~l~t~r and oven driod to give 1.2 mil thick coatings.

WO g3/1613~ t ;~ PCI~/US92/106~?

The tapes were W c~os~lifll~d (cured) using the sarne con~itio~nc as ~i~los~
in E,.~n.~le 1. The peel and shear ~vpc.lies were ~ r~, the results of which ares..~ ;7~d in Table 2.

TABI,E 2 Mullir,.~c~ 1 b~ ph~ n~ rs for solution adhesive .
Cross- Peel from Shcar F-Yq~le !inl~.r W~'.~t% #UV ~cses~q~C (N/dn~) ~nirl) 2 U-bisBP 0.075 1 S9.1 2,690c 2 U-bisBP 0.075 2 54.7 10,000+
2 U-WsBP 0.07S 3 54.7 10,000+
3 C4-bisBP 0.075 1 60.2 10,000+
3 C4-bisBP 0.075 2 56.9 10,000+
3 4bisBP 0.075 3 55.8 3,1SOa 4 PE-bisBP 0.435 1 S6.9 1,350c 4 PE-bisBP 0.435 2 S4.7 10,000+
4 PE-bisBP 0.435 3 54.7 10,000+
nonc 0 70.0 220c . -c= cohcs~_ failurc of the adhesi~e a= adhesive failurc of the adhesi~e 2s + = indicates that test was ~in~d at this point Avcrage peel from glass shown.

J~amplcs 2, 3, and 4 dF~ te the high crosslinl~ng er~ e~.r~ obtainable utili7i~ certain polyfuoc~ n~' bcn-opk-~nes.
CO~PAl~ATIVP PXAMP~ P.~ 4 7 These examples de.~on~t~dte the need for a spacer group between the ben~o~h~-one units which is free, or csS~ y free, of easily a~sh ~e~ le hydl~ge atoms, such as those found on a polyether.

, ' wo 93/16131 2 I 2 9 7 3 ~ Pcr/usg2/lo637 A 90/10 MBA/AA copolymer with inherent viscosity of 0.5 dl g-l was mixed with three dirr~i~,t eth~yleneglycol based bich~ 7~p~p-~o-~es a diethyleneglycolbi~be~Jo~h~o-~e (DG-bisBP) for Co~ e EJ~ample 5, a letracth~luegl~
b ~e ~7oph~ ne (TG-bisBP) for Comparative E~cample 6 and pol~ ykl~eglycol bish~A7~pho~o~c (PG-bisBP) for Comparative Example 7.
ophPr~o~r itself was also incl-~ded as a l~f~n~ (Comparative EJwnple 4). Ihe ben7~0p~0~e content was ~ept equivalent for all thc ~s~ e~s and corre~ponded to a levd of 0.3 wcight percent bc~ pl~e~o~P, on solids. All the ethylace~te soludons were clear and homogeneous and adhesive tapes were preparedaccording to t~c me~ods desc~ibed in ~,~,~o~s c~mples. Thc coating th~ ss of thc dry adbcsivc was 1.0 mils. W cunng was done with only one pass through the curing chamber at ~anable line spoods. Thc tapc l,~p~cs atc somn~d in Tablc 3.

: ~ .

l?

WO 93/16131 . .~ PCr/US92/10637 ~'1'3 j~
'~TABLE 3 F~y!PnPplycol-based b~n~o~lheno~es and a~ la~ curin~
Cross-line speed shear FY~n~DIe linlrf~.r~/lnin) ~min~
Comp. #4 BP 25 10,000+
Comp. #4 BP 75 250c Comp. #4 BP 125 250c Comp.-#5 DG-bisBP 25 10,000+
Comp. #5 DG-bisBP 75 10,000+
Comp. #5 DG-bisBP 125 10,000+
Comp. #6 TG-bisBP 25 10,000+
Comp. #6 TG-bisBP 75 2,000c Comp. #6 TG-bisBP 125 250c Comp. #7 PG-bisBP 25 250c Comp. #7 PGbisBP 75 250c Comp. ~7 PG-bisBP 125 2SOc c = cohesive failure of the adhesive + = indicates that test was ~mina~d at this point Thc clear du; ~sc in W cunng ~ can be as~d with the numb~
of easily ak~h~ble hydrogens in the ~o~in~s (e.g., the number of ether li ~g~s).

PXAMP~.P'~ 7_9 These e~amples (k'~u~ .at~ the ~us~linking of non ~~rylic elastomers with the mul~l~nc~ n~ ophrn~ s used in the present inv~on. The e1~ct~rJ~
listed in Table 4 were dissolved at 10% or 20% solids (dcpenA;flg on the molecular weight of the polymer) in toluene and Clo-bisBP was added to these sol~ti~nc~ The Clo spacer was s~ J for solubility ~ ~ , with the C4 equivalent giving us cloudysolutions. All the solutions were cast to give clear elastomer films, with the only the K~n~ 1107 elastomer samples being slightly hazy.

WO g3/16131 2 1 2 ~ 7 ~ ~:i Pcr/uss2/10637 The el~C~o~c~a were cured under two ...~ ,.. p~ au~ ll~c~ lights Of a PPG UV plocessor. The lamps were at full setting and the samples were each giventhree passes th,~ugh the unit at 75 fpm line speed. The gel content was d~t~ ;n~d by the toluene ~ ;o~ ~e~ i~ above. The results are s~ ~ in Table 4.

UV C1~C~ ;~ of P~ nP-~s with C1Q WSBP
E~cam~le ~lasu~ wd~ht ~i c~ % ~el 7 Vist~ane~c~ LM-MS 2 none detecte~
7 Via~anex~ ~ 5 <5 8 Vistan~ MM 2 38 8 Vistane3c~MM 5 52 9 Kraton~ 1107 2 84 9 ~aton~ 1101 2 83 Tbesc da~ dem~ tlle UV ~osslin~r4 dficiency of Ihc mult~onal benzophenones in non-acrylic daslDmus. The data als~ show that ~ng efficiency d~ends on thc easc of hyd~ogen ab~tion from the bacl~one, thc ~ hvity of thc resulting ~adicals, a~d the m~,le~ar wdght of the dastomer.
EJ~ample 10 dcmonst~ates ~e bigh ao6slin~ng r~ c~ obt~ble with a photossnsitîvc, dastomcnc shoet.

~P~ F. 10 2S A photosensitivc, clas~ome~ic shoct ~vas p~ as follows:
S wdght pC,-~n~ (on a solids basis) of Clo-bisBP was d;ss~l~ in a 20%
solids so1~linn of Kraton~ 1107 dastomer in toluene. Tbe sample was cast on a primed polyester sheet and oven dried to give a S mil thicl~ film. Part of the sheet was co.cs~ with aluminum foil and thc sample was cured in a non-incrted PPG W
~.~ss~r equipped with two .-~cd;- pressure ~ lamps at full setting. The exposure time was about 6 ~ d~ Subsequently, the mask was l~,.,o.ed and the - sample was i ~ .~d in toluene. In a matter of minutes, ~e non c-~d part : 19 ~ ~4h;~
wo 93~16131 ~ Pcr/uss2/106~~
dissolved, whc~as the c~ d part sho~ nly somc swelling. The bo~.n.l~
bet~,veen c ~scd and non c ~scd area was well defined, FXAMP!.F. 11 A ph~cs~ e shect was p,.,~ a~ g to the .~ ~ dG~- ;~d in E~ample 10. Instead of a 209~i solids ~aton'Y 1107 clastomer solution, a 50% solids Trilene~ 65 solution was used to cast the s;unple. Thc curing was donc as d~ibedin E~ample 10 and ag~, tbc non~d part d;~s~h~ readily in thc toluenc, whcrcas the ~-po3~d part showcd some swdling.

~XAMP~ F 1~
This c~amplc demonst~ates the non~ola~le na~re and stability of a mldtifimction~ e cmsslinl~r. Since it can be e~d tba~ higher molecular wdght an~logua are cv~ less vo~a~le, C4~ BP was usod. Compa~ison was made to a ~olymeri~ble beDzop~e (~B~), which Doeds to be inc~po~od in the polymcr p¢ior to a~io~ d b~~s itself, which can be post added to a hot-mdt coa~le polymer.
To da~e ~e effoct of acl~nded hea~ng on thc cmssli~4 effich~ of an acrylate adhesive, lapc s~ wo~ faoc storcd in an oven at 1Q5~C f~r 12 hours. The coa~ng tbicb~ of the adhesive was a~t 1.2 mils. Typically h~r temperatures are used for hot-melt coa~ng, but this ~e was seaocted to avoid polymer degla~on. The tapes tcs~d w~e the ones used for ~mple 1 and Co .~ E~mples 1 and 2.

wo 93/~6131 2 1 2 ~ 7 ~ Pcr/uss2/l0637 TABLE S
Heat eff_cts on cr~s~ Ling ~ffi~iPn~,~y of ~ h~nc~n~s in acrylate adhesives s Peel from glass Shear S~ vle H_at ~ed (N/dm~ ¢Jnin~
Comp ~1 no 60.4 1,530 c Comp #1 yes 65.7 517 c lo Comp #2 no 60.2 9,816 c Comp #2 yes 59.8 10,000+
E~s. 1 no 59.8 10,000+
EJC. 1 yes 60.4 lO,OûO+

c = c~ failure of thc adhesivc + = in~icates that test ~minaled at this point Only ~c avc~age poel value from glass is given.

From the results in Table S it is clear that unless the ba~zophe~one clwslinl~
is copoly~ o~ a non~vola~le mul~ional ben~e crossliDl~r is used, a loss in ~ng efficier~y is to be ~ d for a hot-mdt Fo~d elastomeric composition which is heated for an act~ulod pe~iod of time. Thc multifunctional benzophenone } content of the elastomer can bc t~ilo¢od to any de~red kvel by simple addition or elimination of ~eagent from the mdt, ~ereby offe~ing a A L~ e~
advantage over the co~olyme izable ~BP.

FXAMP~ . 13 A PDMS el~rt~ r was dissolved in a 60/40 toluene/2- propanol ~ U~ of 20% solids. Twodifferent~A-oph~o~s(C~Obis-BPandC~ -rlh~bis-BP)and one ..~ ifi~cl~ l be~oph~none (PDMS~ ultiP") were added at 5% by weight and allowed to d;ssol~e. The solutions were cast to give dastomer films 2 mils in ~h~ S Only th~e solution containing PDMS-multiBP gave a clear film.

WO 93/1613~3 ?~ ;3 - Pcr/usg2/lo63?

The ela~t~ were cured under two r.~;l.... p ~,ssu~ IllC~.~ly lamps of a PPG l~i~ssor. The lamps were at fuU setdng and the samplcs wcre each given threepasses lhrough the unit at 75 ft./min. Iine speed.
The gcl content was de~ined by the toluene e ~ cl;o~ e~h~ describod s above. The results are su.,--- ~-;>~d in Tablc 6.

PDMS-basod mul~-ti~ql c,~os~l;~,rs C~cclinlr~r %
Clo-bisBP 6 C10-metho~cy bisBP 6 PDMS-multiBP 98 15The~c da~ dcmons~ate thc nood for a com~iblc spsccr group to obtain g~eater cm-slin~ng cfficiency.

Reason~blc ~s and modifi~ons arei possiblc from thc foregoing disclosu r without dc~ng from dthcr thc spi~it or sc~ei of thc invention ~ dcfinod 20in thc claims.

Claims

WE CLAIM:

1. A radiation-crosslinkable composition comprising:
(a) an elastomeric polymer containing abstractable hydrogen atoms in an amount sufficient to enable the elastomeric polymer to undergo crosslinking in the presence of a suitable radiation-activatable crosslinking agent; and (b) a radiation-activatable crosslinking agent of the formula:

wherein:
W represents -O, -N-, or -S;

X represents CH3- or Y represents a ketone, ester, or amide functionality;
Z represents an organic spacer which does not contain hydrogen atoms that are more photoabstractable than hydrogen atoms of said elastomeric polymer;
m represents an integer of 0 to 6;
a represents 0 or 1; and n represents an integer of 2 or greater.

2. A radiation-crosslinkable composition according to Claim 1 wherein the elastomeric polymer is a macromolecular material that returns rapidly to its approximate initial dimensions and shape after substantial deformation by a weakstress and subsequent release of that stress as measured according to ASTM D 1456-86.

3. The radiation-crosslinkable composition according to Claim 1 wherein said elastomeric polymer is selected from the group consisting of: styrene-butadiene rubber; styrene-isoprene-styrene block copolymer; styrene-butadiene-styrene block copolymer; ethylene-propylene-diene monomer rubber; polyisobutylene; natural rubber; synthetic polyisoprene; acrylonitrile-butadiene copolymers; polychloroprene;
ethylene-vinylacetate copolymer; silicones; and polyacrylates.

4. The radiation-crosslinkable composition according to Claim 3 wherein said elastomeric polymer is selected from the group consisting of: polyacrylates;
silicones; liquid ethylene-propylene-diene monomer rubber; styrene butadiene-styrene block copolymer; and styre-isoprene-styrene block copolymer.

5. The radiation-crosslinkable composition according to Claim 1 wherein:
X represents phenyl; W represents -O-; Y represents an ester functionality; Z
represents (CH2)2-10;m = 1; a = 1; and n = 2.

6. The radiation-crosslinkable composition according to Claim 1 wherein:
X represents phenyl; W represents -O-; Z represents -CH2-CH2-O-C(O)-NH-R-NH-C(O)-O-CH2CH2-; R represents a divalent aliphatic aromatic, or cycloaliphatic moiety; Y represents an ester functionality m = 1; a = 1; and n = 2.

7. The radiation-crosslinkable composition according to Claim 1 wherein said radiation-activatable crosslinking agent is present in an amount of from 0.01-25 weight percent, based upon the total weight of said radiation-crosslinkable composition.

8. The radiation-crosslinkable composition according to Claim 1 wherein said radiation-activatable crosslinking agent is present in an amount of from 0.1-10 weight percent, based upon the total weight of said radiation-crosslinkable composition.

9. The radiation-crosslinkable composition according to Claim 1 further comprising additives selected from the group consisting of: thermally expandablepolymeric microspheres; glass microspheres; pigments; foaming agents; stabilizers;
fire retardants; viscosity adjusting agents; tackifiers; and plasticiers.