CA2122029A1

CA2122029A1 - Pressure-sensitive adhesive

Info

Publication number: CA2122029A1
Application number: CA002122029A
Authority: CA
Inventors: Patrick G. Zimmerman; Gaddam N. Babu; Lang N. Nguyen; Ingrid E. Blair; George F. Vesley
Original assignee: Individual
Current assignee: 3M Co
Priority date: 1991-12-23
Filing date: 1992-12-23
Publication date: 1993-07-08
Also published as: KR100244373B1; ES2104123T3; WO1993013149A1; EP0618933B1; JPH07502298A; EP0618933A1; DE69220088T2; JP3231772B2; DE69220088D1; US5202361A

Abstract

Radiation-cured compositions are provided which are obtained from starting materials comprising (i) a blend of an acrylate ester and optionally a monoethylenically-unsaturated copolymerizable monomer; (ii) an alpha-olefin polymer; and (iii) a photoinitiator.
The preferred compositions are pressure-sensitive adhesives having good adhesion to both low and high energy surfaces as well as possessing excellent low and high temperature performance properties.

Description

wo 93/13149 212 2 0 2 9 pcr/us92~l1365 PRESSURE-SENSlTIVE ADHESIVE

Field of the Inventjon This invention relates to a radiation-curable composition. This invention 5 also relates to a pressure-sensitive adhesive made from a radiation-curable composition. This invendon further relates to substrates coated with a pressure-sensitive ad- ive.

Back~round of ~e Invention Pressure-sensitive adhesives (~psa~sU) made from the photopolymerization of an alkyl ac~ylate (e.g., isooctyl acrylate) and a polar copolymenzable monomer (e.g., acrylic acid, N-vinyl pyrrolidone, et~.) are well ~nown in the art; see, for example, U.S. Patent Nos. 4,l81,752;
4,364,972; and 4,243,500. Such acrylic-based psa's exhibit good adherence to 15 high energy (i.e., polar) substrates such as metal and painted steel surfaces, but exhibit limited adhesion to low energy (i.e., nonpolar) substrates such as -polyethylene and polypro~ylene. Additionally, whereas the acrylic-based psa's have good high temperature (e.g., 1( ~) performance properties due to the ~ -esence of the polar copolymerizable monomers (which increase the cohesive 20 or internal s~ength of the adhesive), they also exhibit lin~ited adhesion at low temperatures (e.g., -45C). -Pressure-sensitive adhesives basesl upon polymers of alpha (a)-olefins are also well known; see, for example, U.S. Patent Nos. 3,63~,755; 3,954,697;
4,178,272; and 4,288,358 as well as EPO No. 416,921. Psa's based upon ~x-25 olefin polymers tend to e~hibit good adhesion to low energy substrates, but onlymoderate adhesion to high energy substrates. Additionally, they have good low, but limited high, temperature performance properties.
As can be seen from the foregoing discussion, acrylic- and a-olefin-based psa's do not individually exhibit a broad spectrum of desirable adhesive 30 properties. Mere blending together of the two different psa's does not provide an acceptable adhesive because the resulting blend does not produce a psa with WO 93/13149 PCl/US~2/11365 2122029 `

a wide spectrum of perforrnance properties either. It was against this background that the development of a psa material which exhibits good adhesion to both low and high energy substrates as well as good high and low temperature performance properties was sought.
Summary of the Invention By the present invention, it has been discovered that if certain alkyl acrylates, monoethylenically-unsaturated monomers copolymerizable therewith, and polymers of a^olefins are photopolymerized in the presence of a photochemically effective ~mount of a photoinitiator, results in a psa which 10 exhibits a broad spectrum of desirable properties, e.g., both good high and low temperature performance properties and excellent adhesion to low and high `
energy substrates.
Accordingly, in one embodiment of the present invention there is provided a radiation-curable, composition comprising: (a) 100 parts by weight 15 (pbw) of a blend comprising: (i) about 60 to lO0 pbw acrylic acid ester of a monohydric alcohol having an average of 4 to 12 carbon atoms; and (ii) 0 to about 40 pbw monoethylenically-unsaturated monomer copolymerizable with the acrylic acid ester whose homopolymer has a glass transition temperature ~g) greater than about 50C; and (b) lO to 100 p~w polymer of alpha-olefins 20 having a Tg in the range of about -70 to -10C and having a weight average molecular weight (Mw) of about ~5,000 to about 5,000,000, wherein at least 60 mole per~ent of the alpha-olefins have 6 to 18 carbon atoms; and (c) photochemically effective amount of a material selected from the group consisting of:
(i3 photoinitiator of free-radical polymerization;
(ii) photoinitiator of free-radical polymerization and polyfunctional acrylate crosslinker; and (iii) photoinitiator of free-radical polymerization that is also a photocrosslinker .

wo 93/13149 Pcr/VS92/l 1365 In another embodiment, there is provided a pressure-sensitive composition comprising the radiation-cured reaction product of starting materials comprising (a) lO0 parts by weight (pbw) of a blend comprising~
about 60 to lO0 pbw acrylic acid ester of a monohydric alcohol having an S average of 4 to 12 carbon atoms; and (ii) 0 to about 40 pbw monoethylenically- unsaturated monomer copolymerizable with the acrylic acid ester whose homopolymer has a glass transition temperature (Tg) greater than about 50C;
and (b) lO to lO0 pbw polymer of alpha-olefins having a Tg in the range of about -70 to -10C and having a weight average molecular weight (Mw) of 10 about 25,000 to about 5,000,000, wherein at least 60 mole percent of the alpha-olefins have 6 to 18 carbon atoms; and (c) photochemically effective amount of a photoinitiator of free-radical polymerization. --In still another embodiment, the present invention provides a psa madeby the photopolymerization of the foregoing disclosed radiation-curable lS composition. As shown later herein by the examples, the inventive psa's exhibit good adhesion to both low and high energy surfaces and have excellent high and low temperature performance properdes.
In yet another embodiment of the present invention are provided surfaces coated with the inventive psa.
Other aspects, benefits, and advantages of the present invention are apparent from the detailed descnption, examples, and claims.

Detailed Description of the_nvention The acrylic acid esters of monohydric a.~ohols useful in this invention constitute about ~ to lO0 parts by weight (pbw), and preferably about 70-95 pbw, per lO0 total pbw of a blend of the acrylir acid ester and a monoethylenically-unsaturated copolymerizable monomer and are the monofunctional acrylic acid esters of non-tertiary alcohols which have from 4 toabout 12 carbon atoms. Such monomers include, but are not limited to, WO 93/13149 Pcr/US92/l 1365 21~?,029 isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, decyl acrylate, dodecyl acrylate, hexyl acrylate, and butyl acrylate.
Examples of monoethylenically-unsaturated copolymerizable monomers whose homopolymer has a glass transition temperature (Tg) above about 50C
S include, but are not limited to, strongly polar monomers such as acrylic acid,itaconic acid, and substituted acrylamides such as N,N-dimethylacrylamide and N-octylacrylamide; and moderately polar monomers such as 2-hydroxyethyl `acrylate, N-vinyl pyrrdidone, N-vinyl caprolactam, acrylonitrile, and tetrahydrofurfuryl acrylate, and non-polar monomers such as, for example, 10 isobomyl acrylate. The monoethylenically-unsaturated copolymerizable monomer is present in an amount of from 0 to about 40 pbw, and preferably from about 5-30 pbw per 100 total pbw of the blend of acrylic acid ester and monoethyleniG~lly-unsaturated copolymerizable monomer.
The alpha~lefin polymer (also called poly-(a-olefin) or poly~ alkene)) 15 used in the present invention preferably has the general formula:
H-(cH2-cRH)n-H
wberein:
R is one or more monovalent hydrocarbyl group(s) with the proviso that at least 60 mole %, and preferably at least 80 mole %, of the R groups contain from 6 to 18 carbon atoms, and preferably 6 to 12 c~rbon atoms; and n is an integer in the range of from 80 to 50,000.
The homopolymer of ~e a~lefins used in the present invention should have a Tg in the range of about -70C to -10C, and pre~erably from about -25 60~C to -25C. Represen~ative examples of a-olefin monomers that can be used to make the poly(a~lefin) include, but are not limited to, ethylene, propylene, 1-butene, l-pentene, 1-hexene, 1-heptene, l-octene, and branched a-olefins such as 2-methyl-1-butene, 2-ethyl-1-butene, 3-methyl-1-hexene, 2-ethyl-1-hexene, 5-methyl-1-hexene, S-ethyl-l-hexene, etc. Mixtures of these monomers 30 can be copolymerized to poly(a-olefins) using coordination catalysts of the Ziegler-Natta type by methods well known to those sl~lled in the art of polymer wo g3/13149 pcr/us92/l 1365 chemistry. The a-olefin polymer should have a weight average molecular weight (Mw) of about 25,000 to about 5,000,000, preferably from about 50,000 to about 3,500,000; and most preferably from about 50,000 to about 250,000.
The alpha-olefin polymer should be present in the radiation-curable composition in an arnount of from 10 to 100 pbw and preferably from 30 to 70 pbw. ~ ;~
The radiation-curable composition of the present invention contains photochemically effective amounts of one of the following: (i) a photoinitiator of free-radical polymerization; (ii) an initiator of free-radical polymerizationand a polyfunctional acrylate crosslinker; or (iii) a photoinitiator of free-radical 10 polymerization which is also a photocrosslinker. In this application, the term "pbotochemically effective amount of photoinitiator" refers to the amount of photoinitiator n~eeded to initiate free-radical polymerization of the acrylic acid ester and monoethylenically-unsaturated copolymerizable monomers. A
~photocheniically effective amount of crosslinker" is the amount of crosslinker 15 needed to induce crosslinldng between the acrylic polymer chains ~nd/or the poly(a-olefin) chains.
Photoinitiators which are useful include the benzoin ethers, such as ~ ~
benzoin metbyl ether or benzoin isopropyl ether; substituted acetophenones, `
such as 2,2~iethyoxyacetophenone and 2,2~imethoxy-2-phenyl-1- ~ `
20 phenyleth~none ((Irgacure 651 photoinitiator a~ailable from Ciba-Geigy Corp.
or EsacureTM KB-1 photoinitiator available ~rom Sartomer); substituted alpha-ketols, such as 2-methyl-2-hydroxy propiophenone; aromatic sulfonyl chlorides, such as 2-naphthalenesulfonyl chloride; and photoactive oximes, such as 1-pbenyl-1 ,2-propanedione-2-(O ethoxycarbonyl)oxime. Preferably, the 25 photoinitiator is present h~ an amount of about 0.01 to about 5 pbw per 100 pbw of the radiation~urable composition.
Polyfunctional acrylate crosslinkers that may be used in the present invention from about 0.01 up to about 20 pbw per 100 pbw of the radiation-curable composition are acrylic acid esters of polyhyd~ic alcohols such as 1,6-3~3 he~anediol diacrylate (in Chemical Abstracts the name is 2-propenoic acid 1,6-hexanediyl ester {HDDA}) as well as those disclosed in U.S. Patent No.

Wo 93/13149 - Pcr/US92/1136~
2122~2~
-6- ;
4,379,201, such as trimethylolpropane triacrylate, pentaerythritol tetracrylate,1,2-ethyleneglycol diacrylate, 1,2-dodecanediol diacrylate, and the like. Most ;:
preferably, the polyfunctional acrylate crosslinker is present in an amount of about 0.01 to 5 pbw per 100 pbw of the radiation-curable composition.
Materials which function as both photoinitiators and photocrosslinkers in the present invention include the chromophore substituted bistrichloromethyl triazines such as those described in U.S. Patent Nos. 4,391,687; 4,330,590;
and 4~329,384, e.g., 2,4-bis(trichloromethyl)-~(4-methoxyphenyl)-s-tnazine;
2,4-bis(trichloromethyl)-6-(3,4-dimethoxyphenyl)-s-triazine; 2,4-10 bis(trichloromethyl)~(3,5-dimethoxyphenyl)-s-triazineand the like; 2,4-bis(trichloromethyl)~(l-naph~yl~s-triazine; 2,4-bis(trichloromethyl)-~(2-naphthyl)-s-triazine; and 2,4-bis(trichloromethyl)-~(1-(4-methoxynaphthyl))-s-triazine. These compounds and the like are useful as photoactive agents when present in an amount from about 0.01 to about 5 pbw per 100 pbw of the 15 radiation curable composidon. They can be used alone or with a photoinidator (des~ibed above). The usefulness of these cornpounds is in ~heir ability to , impart high tempe~ature shear to the inventive compositions without significan~y affecting peel.
In a preferred embodiment of the present invention, microspheres are 20 added to the radiation-curable composition. When microspheres are present, the polymerized adhesive will have a foam-like appearance. In a most preferred embodiment, hollow polymeric microspheres having average diameters of from S fo 200 micrometers are blended into the radiation-curable composition in arnoun~s of from about 15% to about 75% by volume prior to 25 coating. In this embodiment it is possible to include unexpanded microspheresin the radiation~urable composition and subsequently heat them to cause expansion, but it is generally preferred to mix the expanded microspheres into the adhesive. This process makes it easier to ensure that the hollow microspheres in the final adhesive are substantially surr~unded by at least a thin 30 layer of adhesive. Useful polymeric microspheres are described in U.S. PatentNos. 3,615,972, 4,075,238, and 4,287,308. Microspheres are available from WO g3/13l49 Pcr/uss2/l 1365 2l22o29 ~'.

Kema Nord Plasdcs, under the tradename Expancel. In expanded ~orm, the microspheres have a specific density of approximately 0.02-0.036 g/cc.
Also useful in the radiadon-curable compositions are glass microspheres, as are described in U.S. Patent No. 4,223,067, having an average diameter of 5 from 5 to 200 micrometers, preferably from about 20 to about 80 micrometers.
Such microspheres may comprise 5 % to 65 % by volume of the psa. The psa layer should be at least 3 dmes as thick as the diameter of the glass microspheres, preferably at least 7 times as thick.
In another embodiment, the radiadon-curable composition of this 10 invcntion may be used to make a cellular psa membrane as is described in U.S.Patent No. 4,415,615. -Other useful addenda which can be blended into the radiation-curable composidon include, but are not limited to, fillers, pigments, plasticizers, fibrous reinforcing agents, woven and nonwoven fabrics, foaming agents, 15 an~o~idants, stabilizers, fire retardants, tackifying agents and viscosity adjusting agents. The type and amount of any such ingredients employed preferably will be dete~..ed such that the properties of the resulting composition are not affectéd to the extent the composition fails to perform adequately for its intended puIpose. For example, a particular tackifier 20 employed in a particular amount in a composition intended to be utilized as apressure-sensi~dve adhesive may increase the Tg of the polymer matrix thereby adversely affecting low temperature stability. A lparticular tackifier may also act as a chain ~ansfer agent, thereby lowenng the molecular weight of the resulting composidon. Further, a tackifier may tend to migrate to the surface of the 25 composition upon aging ~ereby reducing adhesion. Hence, preferred pressu~e-sensitive adhesive compositions of the invention do not contain more than about 20 parts by weight of a tackifier per lOO parts by weight of the blend of acrylic acid ester and monoethylenically-unsaturated copolymerizable monorner. More preferred W O 93/13149 P{~r/US92/11365 212202'~

pressure-sensitive adhesive compositions contain no more than about 10 parts by weight of a tackifier per 100 parts by weigh~ of the blend of acrylic acid ester and monoethlenically-unsaturated copolymerizable monomer. Most preferred pressure-sensitive adhesive compositions are either substantially free -5 or totally free of a tackifier.
Other useful fillers include fumed silica. An especially useful filler is hydrophobic silica as disclosed in U.S. Patent Nos. 4,710,536, and 4,749,590.
In another preferred embodiment of the present invention, the psa layer further contains from about 2 to about 15 phr of a hydrophobic silica having a surface 10 area of at least 10 m2/g.
The radiation-curable composition of the present invention is preferably prepared by dissolving the a-olefin polymer in the mixture of free-radically polymerizable monomers, photoinitiator, and photocr~sslinker (if used). The monomers can be added in any order, but preferably the monoethylenically-15 unsaturated copolymerizable monomer is added incrementally last. Glassmicrospheres and other addenda are blended into the solution to provide the psa , composition suitable for coating and cure.
This liquid composition is then coated onto a flexible carrier web using any conventional means such as roller coating, dip coating, knife coating, or 20 e~ctrusion coating and subsequently polymerized in an inert, i.e., oxygen free, atmosphere, e.g., a nitrogen atmosphere as is well-hlown in the art.
The composition can be cured in air by covering a layer of ~e photoactive coating with a plastic film which is substantially transparent to ultraviolet radiation, but impervious to oxygen, and subsequen~y irradiating the25 composition thro~gh that film using fluorescent-type ultraviolet lamps which emit UV light in the wavelength range absorbed by the particular photoinitiator used. Several different lamps w}~h are commercially available may be used.
~hese inelude medium pressure mercury lamps and low intensity fluo~escent lamps, each having various emission spectra and emission maxima between 280 30 and 400 nanometers. For convenience, commercially available fluorescent black lights with a maxima at 351 nanometers and 90% of the emissions WO 93/1314g Pcr/US92/l l36S
2l22o29 ::

between 300 and 400 nanometers (nm) are utilized in the examples illustrating the invention. In general, the total radiation dose should be between about 200-600 milliJoules/cm2. Maximum efficiency and rate of polymerization is dictated by the relationship between emission pr~perties of the radiation source5 and the absorption properties of the photoactive compounds employed. lt is preferable that at least about 75 percent of the radiation be between 300 and 400 nm in the event the preferTed photoinitiator 2,2-dimethoxy-2-phenyl-l-phenylethanone is employed. The photopolymerization can also be carried out in an inert atmosphere, however, tolerance to oxygen can be increased by 10 including an o~idizable tin compound in the composidon as taught in U.S.
Patent No. 4,303,485.
A preferred curing process is one involving inidal exposure of the uncured composidon to electromagnetic radiation of from about 280 to 500 nm wa~rdcngth~and from 0.01 to 20 milliwatts per cendmeter squared (mW/cm2) 15 avcagc ligh~ intcnsity followod by exposure to electro magnetdc radiation of f om about 280 to 500 nm wavelength and having an average light intensity of , g~eater ~an 20 mW/cm2. ;
Psa tapes of the invention may contain more than one layer. Such multd-layered tapes include at least one layer of the cured phase-separated, 20 pressure sensitive adhesive. Such tapes may have a thin layer of a different pressure-sensitive adhesive larninated thereto, so that the adhesive of the invendon is being used as a backing or core layer. The additional layer or layers may be any conventional adhesive known in the art, however, acrylic adhe~ives are preferred. Such multi-layered constructions can be prepared by 25 processes disclosed in U.S. Pat. Nos. 4,818,610; 4,894,259; and 4,895,738.
More preferably, additional adhesive layers include polymers of at least one allcyl acrylate monomer and a copolymerizable monomer v~!hose Tg is above about 50C.

TEST MEl~ODS
The following tests may be used to evaluate tapes of the invention.

W O 93/13149 PC~r/US92/11365 Inherent Viscositv (I.Y.!
The inherent viscosity of the poly(a-olefins) is measured according to ASTM D-857-70 (Reapproved 1977) using ten (10) ml. of a solution of poly(a-olefin) in n-hexane solutions of decrea~ing concentration in a Cannon-Fenske 5 #50 viscometer which are equilibrated in a water bath maintained at 25~C.

Static Shear Value The adhesive films as described in the examples are cut into strips 1.27 cm in width. One of the release liners is removed and the strip is placed with 10 the adhe~ive side down onto an aluminum foil 125 micrometers (~m) thick and 1.6 cm wide. The remaining release liner film is removed from each of the strips to form a "test adhesive tape" and adhered by its adhesive to a flat, rigid stainless steel plate with exactly 1.27 cm length of t~pe in contact with the plate. Before testing, a 1000 g weight at 25C is placed over the bonded area 15 for 15 minutes. Then the plate with the adhered tape is placed either at roomtemperature (RT) or in an air~irculating oven-which has been preheated to ., 70C., and .~ter 15 minutes, a 250 g, 500 g9 or 1,000 g weight is hung from the free end of the tape, with the panel tilted 2 from the ver~ical to insure against any peel forces. The time (in minutes) at which the weight fal1s is the 20 "Sta~c Shear RT(250 g), RT(500 g), RT(1000 g), or 70(500)". The test is discon~nued at 10,000 minutes if ~here is no failure.

T-Peel T-P~el is measured as in ASTM D-187~72 except that the test tapes 25 were 1.27 cm in width and were tested only two hours after being adhered to aluminum foil bacl~ngs. Results a~e reported in Newtons per decimeter (N/dm); Only cohesive failures are reported.
T-Peel provides a quantitative value of cohesive strength and is less sensitive to differences in the adhesion of the psa to the test surface.

WO 93/13149Pcr/US92/1136~
2122~29 90 Peel The adhesive layer to be tested is slit to a width of 1.27 cm and self-adhered to a clean smooth stainless steel plate. A 1.6 cm wide strip of aluminum foil is adhered to the exposed face ~ he adhesive layer under the 5 weight of a 2.25-kg hard rubber-covered steel roller, using 1 pass in each direcdon. After a 20 minute dwell time (at 23C.) or in some instances 72 hours (as indicated in the data tables), the "90 PeelN is measured by moving the free end of the tape away from the steel plate at a rate of about 0.5 cm persecond (using a ~ensile tester). The test specimen is then visually inspected to10 determine the mode of failure. The most common failure mode is by peel off the surfæ, abbreviated (pos)--an adhesive failure where only traces, if any, of adhesive residue is left on the test r~late. The specimen can also fail cohesively, leaving large areas of adhesive reslclue. Cohesive failures are abbreviated ~coh). Unless spscifically indicated in the data tables in the examples, the 15 failure mode was by peel off the surface.
.
~, Cold Slam A rigid vertical steel frame approximately 40 cm square is provided at its upper edge with a similarly dimensioned hinged frame/door. 19.4 square 20 cm (2.54 cm x 7.62 cm) of m~dium density silicone foam is mounted at the lower outer edge of the fixed vertical frame vhere the hinged door impacts when slammed).
Test panels are prepared as follows:
A 12.7 mm x 125 mm pressure-sensitive attachment tape, carried on a 25 r~lease liner, is applied to the 15 mm x 150 mm face of a rigid polyvinyl cnloride test bar which is 6 mm thick. The tape is pressed into place by rollingonce with a 6.8 kg roller. The liner is then removed from the tape and the exposed surface having the psa of the invention is attached to a freshly paintedsteel panel which is 100 mm x 300 mm. Four test bars are attached, in two 30 rows, in the lengthwise direction of the steep panel, with one end of each test bar extending beyond the end of the panel approximately 2.5 cm. After rolling Wo 93/l3149 Pcr/uss2/l 1365 the test panel with a 6.8 kg roller at a rate of 300 mm/min, the panel is allowed to dwel! for 3 days at ambient temperature. The specimen is then conditioned at -40C for approximately 12 hours in the cold chamber, which houses the cold slam fixture as described above. The test panel is then secured S in the fixture, with the test bars and the long dimension of the panel mounted in a horizontal direcdon.
The following test procedure was designed so that some quantitative estimate of cold slam performance could be obtained, rather than simply a pass-fail rating.
The cold slam test is conducted by raising the hinged "door" to a predetermined angle, and releasing it, allowing it to strike the frame and expose the test panel to a cold shock. Ten slams are conducted at each of the five possible slam angles. The slam angle and the number of the slam (1-10) during which any of the four vinyl bars becomes delaminated or detached are 15 recorded. A s1am angle of 23 degrees is used initially. If there have been nofailures after ten slams at the angle, the angle is increased to 45 degrees. This , procedure is repeated until all test bars become detached, or until ten slams at the 180 degree slam angle have been conducted. If failure of one or more bars does occur at a ~pecific stage during the initial ten slams, an additional 10 20 slams are conducted at that stage before advancing to the next slam angle. The results are recorded by documenting the door slam angle/stage and slam number -in which delan~ination begins or failure oecurs. Numerical designation in the form of stages 1-5 correspond to door slam angles of 23, 45, 68, 90 and 180 ;~
degrees, respectively. Lower stage numbers indicate poor cold slam properties, 25 e.g., 1 or 2. Higher stage numbers indicate excellent cold slam properties, --e.g., 4 or 5. The stage, number of slams at each stage, number of failures, and the-failure mode are recorded.

EXAMPLES
This invention will be further illustrated by the following examples, although it will be understood that these examples are included merely for wo 93/13149 Pcr/lJS92/l 136~

purposes of illustration and are not inter~1ed to limit the scope of the invention.
Unless otherwise indicated, all parts ar~ ~y weight.

Preparation of Poly(~-olefins) S
Poly(a-olefin!#l: Poly(1-hexene): I.V. = 2.0 The following reactants were charged (in the order named~ to a dry, a-~ Jn filled, circulating water jacketed glass reacter equipped wi stirrer and dry ice condenser: 200 g dry heptane; 200 g of l-hexene which had been 10 passed through an alumina/silica chromatography column to remove impurities and then dried over molecular sieves; and 0.06 g (0.03 mole) of TiC13(AATiC13TM) catalyst avail; .~le from Stauffer Chemical Co., Inc.
Polymerizaaon was initiated by the slow addition of 8.2 ml. (0.015 mole) of (C2Hs)3Ai (1.9M in toluene). Hydrogen was bubbled through the reaction 15 mixturc at a rate of 60 milliliters per minute (ml/min) to control the rate of reaction and the molecular weight (I.V.) of the poly-(l-hexene) polymer. The polymenzation was exothermic, and the reaction mixture was cooled by circulating water ~rough the reactor jacket to maintain the tentperature at 25C. Polyme~ization continued for five hours at which time one liter of 20 methanol was added to precipitate the polymer. The polymer was washed with additional methanol to remove catalyst residues and dried under vacuum ai 100C. Poly(a-olefin) ~l had a yield of 855to by weight; a Tg of -42C, as dete~mined by differential scanning calorimetry (DSC~; and an I.V. of 1.2 dl/g in n-hexane sol-l~on.
Po!y(a-olefin~ Poly(l-octene!: I.V. = 2.0 and Poly(a-olefin!: ~3 Poly(l-octene!: I.V~ = ~.0 The following reactants were cha~d to the reactor used to make Poly(a~lefin) #l in the order named: 200 g of heptane, 200 g of l-octene 30 (dried over molecular sieves), and 0.06 g of TiCI~ (AATiC13TM) catalyst.
The polymerization was initiated by the slow addition of 0.28 ml of 1.9 M

2122t~2~
- ~4 -(C2H5)3Al which provided a molar ratio of (C2H5)3AI/AATiC13 of 2.5/1Ø
Hydrogen was bubbled through the reaction mixture to control the rate of reaction and molecular weight of the poly-(l-octene) polymer. For Poly(cY-olefin) #2 the hydrogen flow rate was l6 ml/min and for Poly(~x-olefin) #3 it S was 60 ml/min. Polymerization continued for 7.5 hours at 25C after which the resulting polymer was precipitated in excess methanol and dried under vacuum at 100C Poly(a-olefin) #2 had a Tg of -59C and an I.V. of 2.0 dl/g measured in n-hexane solution. Poly(a-olefin) #3 had a Tg of -62C, and an I.V. of 5.0 dl/g measured in n-hexane solution.
'`' Example l Thirty (30) grams of a poly(l-hexene-co-propylene-co-ethylene) mole ratio: 68/30l2, designated TX-1771-98 (available from Eastman Chemicals) was cut into small pieces and placed in a screw cap bottle followed by 95 grams of 15 isooctyl acrylate. This mixture was placed on a shaker for about l2 hours andthen stirred for 4 hours widl a lligh shear mixer. Five (5.0) grams of acrylic -. acid, Q.1 gram of 2,2-dimethyl-2-phenyl-l-phenylethanone (Esacure KB 1 photoinitiator available from Sartomer), and 80 milligrams of hexanediol -~
diac~ylate (HDDA) was added to the mixture. This mixture was agitated until 20 the componen~ were thoroughly mixed and then degassed in a vacuum desic~ator. Adhesive films were prepared by knife coating the mixture onto the -release coated surface of a 50 micrometer biaxially oriented poly~ethyleneterephtha!ate) (PET) film to provide a coa~ing thickness of about 125 micrometers. The coated surface was then covered with a S0 micrometer 25 releas~ coated PE~T film. The "sandwich construction" emerging ~rom the knife ~-coater was cured by exposure to 580 to 600 mJ/cm2 of UV radiation from a bank of fluorescent lamps. The film was cooled by blowing air against the bottom layer during irradiation to keep the temperature of the film below 85 C to avoid wrinkling. Ninety (90) % of the UV radiation was between 30 300 nm and 400 nm with a maximum at 351 nm as measured by an EIT model UR365CHl Radiometer available from EIT, Inc. that was spectrally responsive Wo 93/13149 . Pcr/US92/11365 between 300 and 400 nm. Peel adhesi~n of the adhesive film from stalnless steel, glass, polypropylene, and Paint :j~. 3000 was measured and i~ shown in Table I.

S Comparative Example C1 An adhesive film mixture containing no poly(cY-olefin) was prepared by partially photopolymerizing a mixture of 95 parts IOA, S parts AA, and 0.04 par~s of KB lTM according to the method taught in U.S. Patent No. 4,330,590.
To this mixture was added 0.08 parts per hundred acrylate (pha) of HDDA and 1~ 0.1 pha KB lTM photoinitiator. The adhesive syrup was coated, cured, and tested as described above in Example 1.

Examples 2. 3. and 4 The procedure described in Example 1 was used to prepare three :~
mixtures having an IOA/M ratio of 95/5 and 50,80, and 100 pha of TX-1771-98. To each mixture was added 0.1 pha of ~-1 and 0.08 pha of HDDA and each coated at a thickness of 125 ~m between PEI films as described in Example 1. Test data for each a~hesive film obtained is given in Table 1.
~ .

Wo 93/13149 PCr/US92/11365 21~02Y - 16- ~
Table I
EXAMPLE NUMBER

a-olefin pha 0 30 50 80 100 S
PEEL ADHESION
from:
Stainless Steel 90 (20 Min) N/dm 92 130 151 134 90 (72 Hr) N/dm 120 155 204 141 123 Glass 90 (20 Min) N/dm 116 176 180 141 --~
90 (72 Hr) N/dm 134 165 211 162 ---Polypropylene 90 (20 Min) N/dm 67 99 116 162 ---90 (72 Hr) N/dm 67 ~8 120 165 190 ,"- ' 20 Paint l~CI 3000 90 (20 Min) N/dm 109 116 148 130 ---90 (72 Hr) N/dm 116 134 194 130 99 90 (1 Wk 70 C) N/dm 176 194 211 127 ---The data of Table I show that there is a maxima in polar substrate adhesion (glass, stainless steel) at 50 pha of poly(l-hexene-co-propylene-co-ethylene) (Mole ratio of 68l30l2) and also that with incre~sing amoun~s of the poly(a-olefin) can increase the adhesion of the psa to the low energy surface, polypropylene.

~.

W 0 93/t3149 - 2 1 2 2 0 2 g P(~r/US92/11365 Foam-Like PSA A ~-A foam like psa was prepared from a composition similar to that described in Example C-l with the excel ~n that the monomers used to prepare the syrup were 90 parts IOA and 10 part~ AA. To prepolymerized monomer 5 was added 8 pha of glass microbubbles (Scotchliten' C15/250, available from 3~ Company) and 4 pha of hydrophobic fumed silica (Degussa "Aerosil" 972, available from Degussa, Gmbh, Hanau, Germany). This adhesive mixture then was coated between a pair of PET films and cured (as described in Example 1) to provide a 1.1 mm thick psa.
Examples 5 and 6 (~psa film laminates~
Adhesive mixtures were prepared and coated as described in Example 1 e~cept that the weight ratio of IOA/AA was 90/10 and the poly(alpha olefin) 15 used was poly(a-olefin)#l prepared as described herein earlier. The method of comonomer addition ~_s varied. In Example 5, the AA was added to IOA/poly(l-he~ene) mLlcture all at once following the procedure used i .
Examples 1 - 4 herein. In Example 6, the AA was added drop-wise to prevent the poly-alpha olefin from phasing out. Each mixture was coated at a thickness 20 of 0.14 mm behveen PET films cured, and then laminated to Foam-like psa A
using ~e procedure described in Example 39 of U.S. Patent No. 4,415,615.
The test data are shown in Table II.

Comparative Example C-2 (Comparativepsa film laminate) An adhesive film was prepared using the method of Example C-l except 90 parts of IOA and 10 parts of AA were used. The adhesive was laminated to Foam-like psa A as in Examples S and 6.

Wo 93/13149 Pcr/US92/l 1365 212'~0'~9 Table II ::
EXAMPLE NUMBER
UNITS C-2 5 6 :
a-olefin pha 0 20 20 AA Addition Method None FastSlow PEEL ADHESION from:
10 Stainless Steel 90 (72 Hr) N/dm 127 313 229 Glass 90 (72 Hr) Nldm 137 472 299 iS
Polypropylene 90 (72 Hr) N/dm 3~ 106 130 Paint DCr 3~0 90 (1 Wk 70 C) N/dm 348 514 384 The data of Table II show the sf~ect of the rate of AA addition to the adhesive composition on peel adhesion. Rapid addition results in improved adhesion to high energy surfaces like glass, stainless steel, and automotive paint 25 DCT 3000. The low surface energy adhesion is slightly better when the comonomer is added slowly, however, in both Examples 5 and 6 the adhesion is better than that of comparative Example C 2.

WO 93/13149PCr/US92/11365 Examples 7. 8 9. 10. and 11 -Psa's were prepared using the method of Example 5 with the omission of HDDA and not laminated to foam-like ps~ , but using the following photoactive compounds:
s 1~. ~1~Q0 ybw Photoinitiator & Crosslinker 7 0.08 2,4-bis(trichloromethyl)-6-(3,4-dimethoxyphenyl)-s-triazine 8 0.08 2,4-bis(trichloromethyl)-~(1-naphthyl)-s-triazine Photoinitiator Only 9 0.16 naphthylsulfonyl chloride 0. l 1 2,4-bis(trichloromethyl)-6-methyl-s-triazine and 2-ethyl 9,l~dimethoxydimethylanthracene (1:1) 11 0.09 2,4-bis(trichloromethyl)-~(4-methylphenyl)-s-triazine The ~est data are shown in Table III.
'' : ..

WO 93/13l49 PCr/US92/11365 212~0;~ 20-Table III
EXAMPLE NUMBER
~ITS 7 g 9 10 S PEEL ADHESION from:
Stainless Steel 90 (72 Hr) N/dm 112 88 99 99 137 Glass 90 (120Hr) N/dm 148 158 137 74 116 Polypropylene **
90 (72 Hr) Nldm 67 70 67 88 70 STATIC SHEAR
RT(1000g) Minutes 11766 11766 51.0 11.0 20.0 :~
Failure Mode pass pass pob/r coh coh :~
70C (500 g) Minutes 11767 11769 9.0 0 1.3 Failure Mode pass pass coh coh coh * = Peel off bacldng with residue :~
25 ** = Peel off glass and peel off baclcing (aluminum foil) also coh = Cohesive failure pob/r = Pop off from backing with some residue The test da~a of Table III show that only those triazines which are both crosslinkers and initiators give acceptable static shear performance (Examples 7and 8~.

wo 93/13149pcr/uss2~1 1365 Examples 12. 13. 14. 15. 16 and 17 Adhesive films were prepared according to the method of Example 1, except that IOAIAA (95/5) was used in Examples 12 and 15; IOA/isobornyl S acrylate (85115) was used in Examples 13 and 16; and IOA/N-vinyl pyrrolidone (93l7) was used in Examples 14 and 17, providing compositions having comparable molecular ratio of IOA to high Tg monomer. Examples 12-14 contain 50 phr and Examples 15-17 contain 100 phr of the a-olefin polymer TX-1771-98. For all of Examples 12-17, 0.15 phw of 2,4-bis(trichloromethyl)-10 ~(3~4~imetho~yphenyl)-s-triazine was used in place of HDDA. The adhesive mi~ctures were coated on a single liner and crosslinked in a nitrogen atmosphereto provide 125 micrometer thick films. Test data are shown in Table IV.

Table IV
:
EXAMPLE ' ~BER
UN~TS 12 13 14 _ 16 17 PEEL ADHESION
from:
20 glass 90 (72 Hr) N/dm 70 70 77 77 77 81 polypropylene 90 (20 Min) N/dm 120 137 141 130 148 144 90 (72 Hr~ N/dm 141 137 141 130 148 144 STA~C SHEAR
RT (250 g) Minutes 1974 1638 2983 1726 6194 3420 The failure mode for the static shear test was by cohesive failure.

The data of Table IV show that there is no significant difference in peel adhesion or in static shear performance regardless of choice of comonomer.

wo 93/13149 Pcr/US92/l 1365 21220~9 22-Examples 18 and 19 An adhesive composition was prepared as described in Example 5 with the exception that 0. lS phw of 2,4-bis(trichloromethyl)-6-(3,4-dimethoxyphenyl)-s-triazine was used instead of HDDA. In Example 18, the S composition was coated onto the adhesive mixture of Foam-like pisa A and cured as described in U.S. Patent No. 4,818,610 and in Example l9 the composition was coated between PET films, cured, and laminated to Foam-like psa A as described in Example 5. Test data are shown in Table V.

ComparativeExample C-3 (Comparative layere~ psa! ~:
An adhesive was prepared as described in Example C-l with the exception that 90 parts of IOA and 10 parts of AA were used. The composition ~-~
was coated onto the adhesive mixture of Foam-like psa A as described in ~;
Example 18.
~'.
:.

W093/t3149 Pcr/US92/11365 2l22o2~

Table Y

EXAMPLE NIJMBER
UNITS Ç-2 C-3 18 19 a-olefin pha 0 0 50 50 IOA/AA ratio 90/10 90/10 90/1090/10 PEEL ADHESION from:
stainless steel 90 (20 Min) N/dm 165 148 201 141 90 (72 Hr) N/dm 158 148 201 141 ;:
polypropylene ..
90 (20 Min) N/dm 46 70 148 155 .
90 (72 Hr) N/dm 56 63 197 162 lS
STATIC SHEAR
RT 500 g Minutes 0 104 8048 0 The test data show that better adhesion and superior shear are achieved 20 when the adhesive composition of the invention is coated onto the foamed adhesive than when a film of it is laminated to the foamed adhesive.

Examples 20. 21. 22. and 23 Adhesive films were prepared according to the procedure described in 25 Examples 1-4 with the exception that poly(a-olefin)~2 and poly(a-olefin)#3, prepared as described above and having inherent viscosities of 2.0 and 5.0, respec~ively, were used in place of TX-1771-98. In Examples 20 and 21 poly(a-olefin)~2 was used and in Examples 22 and 23 poly(cr-olefin3#3 was used. The acrylic acid (AA) was added prior to and after pre-30 prepolymerization in Examples 20 and 22 and in Examples 21 and 23,respectively, the prepolymerization in each example being continued to a syrup WO 93/13149 Pcr/uss2/ll365 212202~

having a viscosity of about 3000 cps. The following materials were added to each syrup: 0.1 pha Hl)DA, 8 pha C15/250 Scotch-LiteTM glass bubbles, and 2 pha Aerosir R972 fumed silica. The adhesive mixtures were coated between liners and irradiated to provided crosslinked films l. 1 mm thick. The test data5 are shown in Table VI.

Foam B
Foam-like psa B was prepared as described for the preparation of Foam-like psa A with the exception that the monomer ratio was 95 parts IOA to S
10 parts AA by weight.
'~:

wo 93/13149 - 212 2 0 2 9 pcr/us92/ll36s - 25 - .
Table VI
EXAMPLE NUMBER
UNITS Poam-like 20 21 22 23 I.V. dl/g 2 2 5 5 TENSILE .
STRENGTH kPa 4.1 2.8 2.8 3.4 2~8 :
13LONGATION % ~ i5 768 792 808 863 10 PEEL ADHESION from:
Stainless Steel 90 (72 Hr) N/dm 109 151 120 176 165 15 Glass 90 (72 Hr) N/dm 123 113 120 155 137 STAllC SHEAR
RT 500 g (S.S.) Minutes 104 104 2143 104 7384 70 C 500 g (S.S.) ~inutes 0 0 50 158 34 Slam#per 8/4 2l5 2/S 8l4 2l5 Stage of 8/4 2/5 2l5 1/S 2l5 failure 8/4 2/5 3/5 3/5 3l5 212202~ 26-Example 24 A composition was prepared as described in Example 1 with the exception that poly(l-hexenetpropylene)(60/40), designated as TX 1771-lOO, and 0.15 phw of 2,4-bis(trichloromethyl)-~(3,4-dimethoxyphenyl)-s-~iazine S were used in placed of TX-1771-98 and HDDA, respectively. The mixture was foasned under nitrogen pressure using a 90 mm diameter high shear mixer operating at 900 rpm. The foamed mixture was coated between release coated bia~ually-oriented PET films and cured as described in "Typical Tape-Malcing - Procedure" of U.S. Patent No. 4,415,615. The resulting cellular pressure-10 sensitive membrane was tested and the results are shown in Table VII.

~onlparatiYe Example C-4 A mixture of 95 parts IOA, S parts AA, and 0.04 parts of KB-ln' photoinitiator was prepolymerized to a syrup having a viscosity of about 3000 cps. To the syrup was added 0.15 phw 2,4-bis(trichloromethyl)-~(3,4-dimethox~phenyl)-s-triazine and the resulting.syrup was foamed and coated as desc~ibed in Example24. The resulting cellularpressure-sensitive membrane was ~est~ and the results are shown in Table VII.
Tabl~
EXAMPLE NIJMBE~

P~L ADHESION ~rom:
Stainless Steel 90 (20 Min~ N/dm l2 ll 2~ 90 (72 Hr) N/dm 44 44 Glass 90 (20Min~ N/dm 5 5 90 (72 Hr) N/dm l7 ll Polypropylene 90 (20 Min) Nldm 33 109 90 (72 Hr) N/dm 35 116 WO 93/13149 ~ 1 2 2 0 2 9 PCltUS92/11365 The data of Table VIl shows that ~el adhesion of a cellular pressure-sensitive membrane from polypropylene ai~er 20 min and 72 hr is 109 and 116 N/dm, respectively~ for the membrane containing poly(cY-olefin), but only 33 and 35 Nldm for the membrane containing no poly(a-olefin).
s Exam~les 25-29 Addition of Hydrophobic Fumed Siliea Using the procedure of Example 1, forty (40) grams of poly(a-olefin)#1 was dissolved in 100 grams of IOA. Five aliquots of 20 grams each of this soludon were weighed into 240 ml bottles followed by addition to each of 10 sufficient acrylic acid, KB 1 photoinitiator, ~nd 2,4-bis(trichloromethyl)-~(3,4 dimethoxyphenyl)-s-triazine to provide solutions that were 90/10 IOAJAA, 0.1 pha by weight KB l, and 0.15 pbw 2,4-bis(trichloromethyl)-~(3,4-dimethoxyphenyl)-5-triazine. The aliquots were stirred to dissolve these addenda. The following amounts of hydrophobic fumed silica (Degussa 15 Aerosil~-972) were added respectively to the five aliquots: none, 650, 865, 1,080, and 1,300 milligrams, i.e., to provide.0, 3, 4, 5, 6 pbw of adhesive , composition. The components were again stirred to provide a homogeneous mixture. The solutions were aged in the dark for 18 hours at r~om temperature, degassed in a vacuum desiccator. The adhesive compositions were 20 coated on a single lina and radiation cured under nitrogen to yield adhesive films of 125 micrometer thickness. Test results are shown in Table VIII. The static shear test (less ~an 104 minutes) failed aclhesively.

W0 93/13149 Pcr/US92/11365 212~029 28-Table VIII
EXAMPLE NUMBER

5 Silica loading pbw 0 3 4 5 6 PEEL ADHESION from:
stainless steel 90 (72 Hr) Nldm 9093 102 102 104 polyprowlene 90 (72 Hr) N/dm 7782 93 88 88 STATlC SHEAR
Room Temp (1000 grams) Minutes 103104 104 104 104 70C (500 g~ns) Minutes 14257 6599768 104 Example 30 The procedure of Bxample 1 was repeated to prepare a poly(a-15 olefin)#l/polyacrylate symp using the following reactants: 20 gr~uns of poly(a-olefin)#1, 95 g~ams of isooc~l acrylate, 5 grams of acrylic acid, 0.1 gram of Esacure KB 1~ photoinitiator, and 100 milligrams of hexanediol diacrylate (HDDA). Kni~e coated adhesive films were prepared using the process of Exarnple 1. The cured adhesive film had a ~el adhesion from glass of 183 20 N/dm. The static shear adhesion of this film was not measured.

mparative Example ( -5 7he following materials were placed in a glass reaction bottle: 95 grams of isooctyl acrylate, S grams of acrylic acid, 20 grams of poly[a-olefin)#1]
25 (I.V. 1.2 dlJgm), 100 grams of toluene, and 0.2 grams of benzoyl peroxide.
The reaction bottle was purged with nitrogen and sealed. It was placed in a 60C bath and tumbled therein for 24 hours to polymerize the acrylic monomers. The resulting solution of acrylic and ~-olefin polymers was knife coated onto a 37 micromet~r polyester film to provide a dry coating thickness 30 of 38 micrometers. The ccated film was equilibrated ~or 24 hours and Wo 93/13149 2 1 2 2 0 2 9 Pcr/us92/l 1365 - 2g -thereafter tested under constant temperature and humidity. Adhesive had a peel adhesion of 64 N/dm on glass and shear of lO minutes on stainless steel.

Comparative Example C-6 To the solution of the adhesive composition from the above reaction was added 1 per cent of benzophenone and knife coated onto a 37 micrometer polyester film to provide a dry coating thickness of 38 micrometers. The coated film was equilibrated as above and was cured in nitrogen with 250 mJ/cm2 of energy using medium pressure mercury lamp. The cured adhesive 10 has a peel adhesion of 62 N/dm from glass and shear of 550 minutes on stainless steel.

Example 31 The procedure of Example l was repeated to prepare a poly(a-l5 olefin)#l/polyacrylate using the following reactants: 20 grams of poly(a-~olefin)#l, 100 grams of isooctyl acrylate, O.l gram of 2,2~imethyl-2-phenyl-1-phenylethanone (Esacure KB l' photoinitiator, and 100 milligrams of ;~
hexanediol diacrylate (HDDA). ~Cnife coated adhesive films were prepared using the process of Example l. The peel adhesions of this film from various 20 substrates are shown in Table IX. The static shear adhesion of this film wasnot measured.

Table IX
Example 31 25 Peel Adhesion Stainless Steel 90 (72 hr) N/dm - 49.5 Glass 90 (72 hr) N/dm 52.8 Polypropylene 90 (72 hr) N/dm 91.5 WO 93/13149 Pcr/US92/1 1365 .~

Example 32 A poly(Q~-olefin)/polyacrylate was prepared following the procedure of -Example 1 employing as reactants 40 grams of TX-1872-112 (a 0.8 I.V.
S polyhexene from Eastman Chemicals), 100 grams of isooctyl acrylate, 11 grams of acrylic acid, 0.1 gram of 2,2-dimenthyl-2-phenyl-1-phenylethanone (Esacure KB-l'Y) photoinitiator and 0.23 grams of 2,4-bis(trichloromethyl)-6-(3,4~imethoxyphenyl)-5-triazine. An adhesive film was prepared following the procedures of Example 1 except that the film was cured by exposure first to ;
10 lJV radiation of an intensity of about 1.75 mW/sq cm for about 25% of the Iength of the coater and then to U.V. radiation of an intensity of about 0.75 mW/sq cm for the remaining length of the coater. The composition was ;~
exposed to a tota1 of about 300 milliJoules per cm2 of energy. The peel performance of the adhesive was as indicated in Table X below.
~ , Examples 33-34 The procedure of Example 1 was repeated to prepare for Examples 33 and 34 a poly(Qr-olefin)/polyacrylate employing as reactants 30 grams of TX~
1872-138 (a 1.6 I.V. polyhexene from Eastman Chemicals), 100 grams of ~;
20 isooctyl acrylate, 11 grams of acrylic acid, 0.1 g~am of 2,2-dimethyl-2-phenyl-l-phenyle~hanone (Esacure KB-l~) photoinitiator, and 0.23 grams of 2,4-bis(trichloromethyl)-~(3,4~imethoxyphenyl)-5-triazine. The composition of Example 34 further included 9 grams of Aerosir R 972 which was added to the mixture following the procedure of Examples 25-29. The cure profile for 25 both compositions was described in Example 32 was employed and adhesion performance results were as indicated in Table X below.

WO 93/13149 2 1 2 2 0 2 9 pcr/us92/11365 Table X
EXAMPLE NUMBER

S PEEL ADHESION
from: ~
Stainless Steel 90 (72 Hr) N/dm 98.5 68 66 10 Stainless Steel 90 (72 Hr) N/dm 90.3 63 75 STATIC SHEAR
at room te~q~perature Minutes NDl 328 2017 at 70C Minutes NDl 59 197 1 ND: Not de~ennin~?' -.;~

Claims

We Claim:

1. A composition which is the radiation-cured reaction product of starting materials comprising:
a) 100 parts by weight (pbw) of a blend of:
i) 60 to 100 pbw of an acrylic acid ester of a monohydric alcohol having an average of 4 to 12 carbon atoms; and ii) 0 to about 40 pbw monoethylenically-unsaturated copolymerizable monomer whose homopolymer has a Tg greater than about 50°C;
b) 10 to 100 pbw of polymer of an alpha-olefin having a Tg in the range of about -70°C to -10°C and having a weight average molecular weight of about 25,000 to about 5,000,000 wherein at least 60 mole percent of the alpha-olefin has 6 to 18 carbon atoms; and c) photochemically effective amount of a photoinitiator of free-radical polymerization.

2. A composition according to Claim 1, wherein said component a) of said starting materials comprises about 70-95 pbw of said acrylic acid ester.

3. A composition according to Claim 1, wherein said component a) of said starting materials comprises about 5-30 bpw of said monoethylenically-unsaturated copolymerizable monomer.

4. A composition according to Claim 1, wherein said monoethylenically-unsaturated copolymerizable monomer is a strongly polar monomer.

5. A composition according to Claim 1, wherein said monoethylenically-unsaturated copolymerizable monomer is a moderately polar monomer.

6. A composition according to Claim 1, wherein said component b) of said starting materials is present in an amount of comprises 30 to 70 pbw per100 pbw of said component a).

7. A composition according to Claim 1, wherein said alpha-olefin p????er h?? Tg in the range of about -60°C to -25°C.

8. A composition according to Claim 1, wherein said alpha-olefin polymer has a weight average molecular weight of about 50,000 to about 3,500,000.

9. A composition according to Claim 1, wherein said alpha-olefin polymer has a weight average molecular weight of about 50,000 to about 250,000.

10. ? composition according to Claim 1 wherein at least 80 mole percent of sai? ?lpha-olefins of said alpha-olefin po???er have 6 to 12 carbon atoms.

11. A composition according to Claim 1, wherein said photoinitiator is one selected from the group consisting of a benzoin ether, a substituted acetophenone, a substituted alpha-ketol, an aromatic sulfonyl chloride, and a photoactive oxime.

12. A composition according to Claim 1, wherein said photoinitiator is a trihalomethyl-s-triazine.

13. A composition according to Claim 1, wherein said starting materials further comprise hollow polymeric microspheres.

14. A composition according to Claim 1, wherein said starting materials further comprise glass microspheres.

15. A composition according to Claim 1, wherein said starting materials further comprise hydrophobic silica.

16. A composition according to Claim 1, wherein said starting materials comprise no greater than about 10 pbw of a tackifier per 100 pbw of said component a).

17. A composition according to Claim 1, wherein said starting materials are substantially free of a tackifier.

18. A composition according to Claim 1, which is a pressure-sensitive adhesive.

19. A pressure-sensitive adhesive tape comprising the composition of Claim 18 coated on a suitable substrate.

20. A pressure-sensitive adhesive tape of Claim 19, wherein said substrate is siliconized poly(ethylene terephthalate).

21. A pressure-sensitive adhesive tape of Claim 19, wherein said pressure-sensitive adhesive has a cellular structure.

22. A pressure-sensitive adhesive tape of Claim 19, wherein said pressure-sensitive adhesive is in the form of a cellular membrane.

23. A radiation-curable composition comprising:
a) 100 parts by weight (pbw) of a blend of:

i) 60 to 100 pbw of an acrylic acid ester of a monohydric alcohol having an average of 4 to 12 carbon atoms; and ii) 0 to about 40 pbw monoethylenically-unsaturated copolymerizable monomer whose homopolymer has a Tg greater than about 50°C;
b) 10 to 100 pbw of polymer of an alpha-olefin having a Tg in the range of about -70°C to -10°C and having a weight average molecular weight of about 25,000 to about 5,000,000 wherein at least 60 mole percent of the alpha-olefin has 6 to 18 carbon atoms; and c) photochemically effective amount of a photoinitiator.