MXPA97003096A - Adhesive sensitive to semi-structural pressure stable, low current temperature - Google Patents

Abstract

A curable pressure sensitive adhesive having a long storage life is disclosed comprising: (1) at least one polymer polymerized by free radicals, (2) at least one cationically polymerizable monomer, (3) a photoactivatable catalyst system. for the cationically polymerizable monomer comprising at least one organometallic complex salt or at least one onium salt, and (4) optionally a monohydric or polyhydric alcohol, wherein there is essentially no conversion of the cationically polymerizable monomer from the sensitive adhesive to the the curable pressure when stored in a way that excludes radiation, and methods for manufacturing the same

Description

STABLE SENSITIVE ADHESIVE STABLE I-STRUCTURAL PRESSURE, OR LOW CURING TEMPERATURE Background of the Invention Embodiment of the invention This invention relates to curable pressure sensitive adhesives, comprising (meth) acrylic polymers and pre-polymers of Epoxy, where pressure sensitive adhesives have long shelving durations and exhibit excellent adhesion strengths when cured, and cured pressure sensitive adhesives are particularly useful as structural or semi-structural adhesives.

Description of the Related Art The removal of solvents from polymeric articles and coatings and from the processes by which they are produced is the subject of intense efforts throughout the world. These efforts have included the development of formulations of high solids content and 100% solids polymerized by thermal, photon and energy means to produce a wide variety of polymeric products. Such formulations include polymers prepared from acrylic, urethane and ethoxy precursors and mixtures thereof. However, many of these processes have significant disadvantages, either related to processing or related to the performance characteristics of polymeric products. REF: 24509 A number of polymerizable systems comprise mixtures of acrylate monomers and urethane precursors or acrylate monomers and epoxy monomers have been described in the art. See, for example, U.S. Patent Nos. 5,086,088 and 5,262,232, EPA 476,822 and WO 91/16387. The processes for these systems have a variety of disadvantages. For example, acrylate monomers by themselves are generally polymerized in solution. While solution polymerization is useful for controlling the exothermic reaction of the polymerization characteristic of the acrylate monomers, there is still a need to discard the organic solvents used in such a process. Alternatively, the acrylate monomers can be polymerized in bulk processes with photon beam or photon beam, which normally requires an inert atmosphere. However, once the mixed acrylate-epoxy polymerizable mixtures are exposed to radiation, that is, the radiation necessary to initiate the polymerization of the acrylate component, the epoxy component is invariably exchanged. The epoxy component can begin to cure, albeit slowly, although the epoxy initiators have not been fully initiated. Such a gradual curing process reduces the storage life of the epoxy component. This is not in general a serious limitation, unless there is a desire to maintain a different period of time between the curing of the acrylate component and the component? of epoxy.

Many double curing systems have been described. For example, there are systems that have multiple components, each with the appropriate catalysts that cure at essentially the same wavelength. Additionally, there are systems that are multi-component, again with the appropriate catalysts that cure at different wavelengths. Many of these systems have been described in the art, for example, see U.S. Patent Nos. 5,252,694, 5,262,232, 4,156,035, 4,277,978, 4,428,807, 4,717,605, 4,657,779, 4,694,029, 4,707,432, 4,950,696, 4,985,340 and 4,849,320. In many cases, the photoinitiation of the acrylate and epoxy monomers is carried out using different wavelengths of radiation, in order to separate, in time, the curing of the two systems. Normally, such double curing methods are only moderately successful in separating the two curing (i.e., overlaying the radiation wavelengths such that the systems have limited storage life following the initial irradiation step. double component system in which the acrylate polymer is prepared in a solvent that is subsequently distilled, followed by mixing with an epoxide precursor that can be polymerized under UV light irradiation, is an alternative method to prepare double component compositions. However, this process produces a "release on demand" adhesive that becomes easily non-adherent by exposure to actinic radiation. See, for example, U.S. Patent No. 4,286,047.

Reactive extrusion is another method for thermally polymerizing bulk acrylic monomers using a wiped film extrusion apparatus. See, for example, U.S. Patent No. 4,619,979. However, this method is inapplicable for acrylate monomers that crosslink or form gels during polymerization. As a result, acrylic polymers made by this method tend to show limited utility as high strength adhesives. The addition of cationically polymerizable monomers (eg, epoxies during or after polymerization of acrylate and polymerization thereof to prepare double component adhesives) has not yet been addressed.What is not described in the art is a composition that exhibit the desirable properties of a conventional pressure sensitive adhesive (e.g., a polyacrylate) and a thermosetting resin (e.g., an epoxy resin), having a significy longer shelf life, after the PSA portion is has successfully cured, such compositions as are known in the present.

BRIEF DESCRIPTION OF THE INVENTION The present invention discloses a curable pressure sensitive adhesive which after curing provides a semi-structural or structural adhesive, wherein the pressure sensitive adhesive comprises: (1) at least one polymer obtained from the polymerization of at least one free radical polymerizable monomer, (2) at least one cationically polymerizable monomer, (3) a photo-activatable catalyst system for the cationically polymerizable monomer comprising either at least one organometallic complex salt or at least one onium salt; and (4) optionally, a monohydric or polyhydric alcohol wherein there is essentially no conversion of the cationically polymerizable monomer of the curable pressure sensitive adhesive, for at least 10 days at 20 ° C, 50% relative humidity, when stored from a way to exclude actinic radiation, which is capable of activating the catalytic system. In a second aspect of the invention, there is provided a method for preparing a curable pressure sensitive adhesive, comprising the steps of: (1) preparing a polymerizable composition comprising a mixture of: (a) at least one polymerizable monomer by free radicals, (b) at least one thermal free radical initiator, (c) at least one cationically polymerizable monomer, (d) a photo-activatable catalyst system for the cationically polymerizable monomer comprising at least one salt of organometallic complex or at least one onium salt, and (e) optionally a monohydric or polyhydric alcohol, and (2) applying sufficient thermal energy to the mixture to essentially complete the polymerization of the thermally free radical polymerizable monomer. While any thermally initiated free radical polymerization process is useful in the practice of step 2 of the present invention, reactive and thermal extrusion polymerization in the presence of a heat transfer medium are particularly useful processes. Advgeously, the photoactivatable cationic catalyst is not affected under the operating parameters of the thermal energy application. This provides a stable pressure sensitive adhesive, which after application to a substrate can subsequently be irradiated in situ to provide a structural or semi-structural adhesive. In the present invention, a thermally controlled polymerization process for the production of adhesives and adhesive coated tapes with acceptable product properties can be obtained by using a thermal polymerization step carried out in conjunction with a thermal buffer comprising a process of heat transfer that has a relatively high heat transfer coefficient as a characteristic, such as forced conversion using flow water. Preferably, the adhesives are based on acrylic, which exhibit annoying exothermic reactions and sometimes limit the speed of the polymerization process. Therefore, the process of the invention for the production of adhesives comprises allowing a carrier fabric coated with a free radical polymerizable composition to remain in a thermal buffer for a sufficient time to effect the conversion of the coating to an adhesive, so much that the exothermic reaction is controlled to maintain the reaction temperature at a temperature of 20 ° C of the temperature of the thermal buffer solution. The thermal buffer is characterized as a system for heat transfer, wherein the heat transfer coefficient is at least 25 W / (m2-K) depending on the particular polymerizable mixture, it may be advantageous to exclude oxygen from the zone of polymerization. The coating on the carrier fabric can be a thermally polymerizable mixture, substantially free of solvents, wherein the polymerizable mixture comprises at least one free radical polymerizable monomer, at least one thermal initiator and optionally at least one crosslinking agent, at least one cationically polymerizable monomer and photo-activatable cationic catalyst system. Preferably, the monomers polymerizable by free radicals are predominantly acrylic based monomers. In another embodiment of the present invention, a polymerizable composition is coated between a first and a second carrier fabric, to form a sandwich and then processed as explained above. Advantageously, there is no need to remove oxygen from the polymerization zone.

A particularly useful feature of this invention is an adhesive system having the combined properties of a pressure sensitive adhesive (for easy application) and a thermosetting resin (for a permanent, strong structural or semi-structural bond). In addition, the adhesive system of the present invention exhibits a significantly longer shelf life after the pressure sensitive portion (the free-radically polymerizable monomers) have been fully cured than similar compositions that are known in the art. . Another advantage of the present invention is that the adhesive systems are prepared as 100% reactive coating compositions, to substantially eliminate the waste of industrial solvents, while also reducing energy consumption. The method of the invention provides a significant advantage over the prior art in that the initial polymerization of the free radical polymerizable monomer (s) is carried out in a manner that does not affect the polymerization of the monomer (s) (s) cationically polymerizable (s), neither activates the cationic polymerization catalyst (i.e., the organometallic complex salt or onium salt), which is thermally stable and photochemically labile. This ability to separate the two curing allows the adhesive systems of the invention to have very long storage lives in the PSA state before application and use. The pressure sensitive adhesive can be converted to a structural or semi-structural the adhesive: (a) applying sufficient irradiation to the curable PSA to activate the photocatalytic system photoactivatable, and (b) providing sufficient time and / or thermal energy to effect polymerization essentially complete of the cationically polymerizable monomer. A further advantage of the present invention is provided by the temperatures of thermal curing lower of (the) monomer (s) polymerizable (s) cured (s) cationically opposed to the temperatures of thermal curing required for (the) monomer ( s) cationically cured from known systems. Commonly, the temperatures required to cure the cationically cured monomers, such as epoxies, may be so high as to prevent the use of certain low temperature melting temperature sensitive substrates or reinforcements. In contrast, the photoactivatable catalyst systems used in the present invention are such that the cationic cure to form the structural or semi-structural adhesives can occur at lower, less harmful temperatures. In addition, the preferred present method for controlling the exothermic reaction of acrylate polymerization in a heat exchange medium allows control of the entire temperature during the step of preparing the pressure sensitive adhesive. The subsequent photo-activation and curing of the component? of thermosetting resin, this is the epoxy component of the adhesive system increases the resistance to adhesion to the semistructural level, which can not be achieved by the traditional pressure sensitive adhesives.

Still another advantage of the invention is obtained due to the ability to control the latency at room temperature of the photopolymerization catalyst, used in the curing of the thermosetting resin. Thus, reasonable work times after photolysis of the composition can be performed (in the order of tens of minutes), to allow the positioning (and repositioning) of the substrates to be adhered before a permanent bond is obtained. The low temperature of the curing of the thermosetting resin makes the adhesive of the present invention, especially suitable for those applications where higher temperatures can not be tolerated, due to the limitations of the equipment or the use of thermally sensitive substrates (for example, thermoplastics). In still an aspect of the present invention, the curable pressure sensitive adhesives can be prepared according to the method comprising the steps of: (1) preparing a first polymerizable composition comprising a mixture of (a) at least one monomer polymerizable by free radicals, (b) ) at least one free radical initiator, (2) apply sufficient energy to the mixture to effect the essentially complete polymerization of the free radical polymerizable monomer; (3) mixing to the polymerized composition, a second polymerizable composition comprising a mixture of: (a) at least one cationically polymerizable monomer, (b) a photoactivatable catalyst system for the cationically polymerizable monomer, comprising at least one salt of organometallic complex or at least one onium salt, and (c) optionally, a monohydric or polyhydric alcohol. Alternatively, the cationically polymerizable monomer can be added to the first polymerizable composition, wherein the photoactivatable catalyst system for the cationically polymerizable monomer is added after the first polymerizable composition has been polymerized. The polymer polymerized by free radicals can be prepared in any of a variety of means known in the art, such as photopolymerization or thermal polymerization, any of which can be carried out in volume (100% solids) or in solution. If carried out in solution, the solvent must be removed before the fusion mixture. Preferably, the polymer polymerized by free radicals is prepared by bulk photopolymerization with the cationically present polymerizable monomer. Advantageously, in contrast to the known, energy-curable epoxy-acrylate compositions, such as those described in U.S. Patent No. 5,252,694 (column 7, line 57 to column 8, line 56), esters that thermally decompose are not required as accelerators / additives in the present formulations. As used in this application: "acrylate syrup" means a composition comprising a partially polymerized mixture of (meth) acrylates only or a partially polymerized mixture of non-polymerized epoxy (meth) acrylates and monomers; "containing (meth) actable" means materials that are essentially free of (meth) acrylic acid, but which contain a (meth) acrylate monomer, a mixture of (meth) acrylate monomers, or a mixture of (meth) acrylate -epoxy, furthermore, the terms "(meth) acrylate" and "(meth) acrylic" include acrylates and methacrylate and acrylic and methacrylic respectively; "thermal shock absorber" means a system that brings the material in contact with the shock absorber, such as the coated fabric, to the temperature of the shock absorber and tends to keep the material inside the shock absorber at a relatively constant temperature; "heat transfer coefficient of the thermal buffer" means the effective heat transfer coefficient for the heat transfer process that occurs within the buffer from the coated carrier fabric to the thermal buffer. This heat transfer coefficient can be either a coefficient of heat transfer by convection, when a water bath is used for the thermal buffer or a conduction heat transfer coefficient, for example, when a heated metal surface It is used for the thermal buffer.

"Bi-reactive monomer" means a monomer containing at least two polymerizable groups by free radicals or two cationically polymerizable groups and does not contain both types of groups; "bifunctional monomer" means a monomer containing at least one free radical polymerizable group and at least one cationically polymerizable group; "group" or "monomer" or "anion" or "ligand" means chemical species that allow substitution or that can be substituted by conventional substituents that do not interfere with the desired product, for example, the substituents may be alkyl, alkoxy, aryl , phenyl, halo (F, Cl, Br, I), cyano, nitro, etc.

Description of the Preferred Modes The cationically useful polymerizable monomers in the present invention include, but are not limited to, epoxy-containing materials, alkyl vinyl ethers, cyclic ethers, styrene, divinylbenzene, vinyltoluene, N-vinyl compounds, cyanate esters, 1- alkenes (alpha olefins), lactams and cyclic acetals. The cyclic ethers that can be polymerized according to this invention include those described in Frisch and Reegan Ring-Opening Polymerizations Vol. 2 (1969). Suitable 1,2-cyclic ethers include monomeric and polymeric types of epoxides. Particularly suitable are the 1,2-epoxides, aliphatic type, cycloaliphatic and glycidyl ether. A wide variety of commercial epoxy resins are available and are listed in Lee and Neville Handbook of Epoxy Resins (1967) and P. Bruns Epoxy Resin Technology (1968). Representative of the 1,3 and 1,4-cyclic ethers which can be polymerized according to this invention are oxetane, 3,3-bis (chloromethyl) oxetane and tetrahydrofuran. The cationically additional polymerizable monomers are described in U.S. Patent No. 5,252,694, column 4, line 30 to column 5, line 34, the disclosure of which is incorporated herein by reference. Preferred monomers of this class include EPON ™ 828, and EPON ™ 1001F and the ERL series of cycloaliphatic epoxy monomers such as ERL-4221 ™ or ERL-4206 ™; the most preferred monomers are from the ERL series due to their lower curing temperatures. Ethylenically unsaturated free radical polymerizable monomers useful in the invention include, but are not limited to (meth) acrylates and functionalized vinyl ester materials. Of particular use are (met) acrylics. The starting material may consist of either monomers or oligomers, as described in U.S. Patent No. 5,252,694 in column 5, lines 35-68. Alternatively, useful monomers comprise at least one functionality free radical polymerizable. Examples of such monomers include specifically, but not exclusively, the following classes: Class A - esters of acrylic acid of an alkyl alcohol (preferably a non-tertiary alcohol), the alcohol contains from 1 to 14 (preferably from 4 to 14) carbon atoms, and includes, for example, methyl acrylate, acrylate of ethyl, n-butyl acrylate, t-butyl acrylate, hexyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isobornyl acrylate, phenoxyethyl acrylate, decyl acrylate, and dodecyl acrylate; Class B - esters of methacrylic acid of an alkyl alcohol (preferably a non-tertiary alcohol), the alcohol contains from 1 to 14 (preferably from 4 to 14) carbon atoms and includes, for example, methyl methacrylate, methacrylate ethyl, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate and t-butyl methacrylate; Class C - (meth) acrylic acid monoesters of polyhydroxyalkyl alcohols such as 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, the various butyl diols, the various hexanediols, glycerol, in such a way that the Resulting esters are referred to as hydroxyalkyl (meth) acrylates; Class D - multifunctional (meth) acrylic esters, such as 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, glycerol diacrylate, glycerol triacrylate and neopentyl glycol diacrylate, although these monomers are generally not preferred for the reactive extrusion or fusion mixing; Class E - macromer (metha) acrylates, such as (met) acrylate-terminated (meth) acrylate-terminated styrene oligomers and (meth) acrylate-terminated polyethers, as described in PCT patent application WO 84/03837 and the European patent application EP 140941; Class F - (meth) acrylic acids and their salts with alkali metals, including, for example, lithium, sodium and potassium, and their salts with alkaline earth metals, including, for example, magnesium, calcium, strontium and barium. Although the curing temperatures of the cationically polymerizable monomers can be affected, it is also within the scope of the present invention to also use a seventh class of monomers by free radicals, ie "Class G" monomers. Class G monomers include nitrogen-carrying monomers selected from the group consisting of (meth) acrylonitrile, (meth) acrylamide, N-substituted (meth) acrylamides, N, N-disubstituted (meth) acrylamides, the latter of which may include substituents of the 5- and 6-membered heterocyclic rings comprising one or more heteroatoms and methyl-substituted maleonitrile and N-vinylactams, such as N-vinylpyrrolidinone and N -vinylcaprolactam. Two other criteria for free radical monomers are preferred, but are not required: (a) these monomers must be miscible with the epoxy monomer (s) and (b) the free radical monomers are preferably chosen from such that their copolymers have Tg compounds in the range of 30 ° C or less, as calculated by, for example, the Fox equation, Bull Am. Phvs. Soc. 1. 123 (1956). The bifunctional monomers can also be used and examples which are useful in the invention possess at least one free radical and a cationically reactive functionality per monomer. Examples of such monomers include, but are not limited to, glycidyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl acrylate. Suitable salts of the organometallic complex include those described in U.S. Patent No. 5,059,701 and such a description is incorporated herein by reference. In addition to those described in U.S. Patent No. 5,059,701, organometallic complex salts, described in EPO No. 109,851, are also useful in the present invention. The salts of the organometallic complex useful in the present invention have the following formula: [(L'KL ^ MT Y. wherein Mp represents a metal selected from the group consisting of Cr, Mo, W, Mn, Re, Fe and Co; L1 represents 1 or 2 ligands contributing with pi-electrons which may be the same or different ligand selected from the group of: eta3-allyl, eta5-cyclopentadienyl, and eta7-cycloheptatrienyl, and substituted and unsubstituted eta6-aromatics selected from compounds substituted eta6-benzene and eta-benzene and compounds having 2 to 4 fused rings, each capable of contributing 3 to 8 pi-electrons to the valence of Mp; L2 represents none or 1 to 3 ligands that contribute to an equal number of sigma electrons that can be the same or different ligand, selected from the group of: carbon monoxide, nitrosonium, triphenylphosphine, triphenyltin and phosphorus, arsenic and antimony derivatives, with the condition that the total electronic charge, contributed to Mp, results in a net positive residual charge of q to the complex; q is an integer that has a value of 1 or 2, the residual charge of the complex cation; Y is a complex anion containing halogen, selected from BF4", AsF6", PF6 ', SbF5O, SbF6"and CF3SO3', and n is an integer having a value of 1 or 2, the number of complex anions required to neutralize the charge q on the complex cation The preferred organometallic initiators are the cyclopentadienyl iron (CpFeArenos), and preferably, SbFβ "is the counter ion. CpFe (arenes) are preferred because they are very thermally stable and still excellent photoinitiation catalysts. It has been described that useful cationic photoinitiators comprising onium salts have the structure AX, wherein: A is an organic cation, selected from diazonium, iodonium and sulfonium cations, more preferably A is selected from diphenyliodonium, triphenylsulfonium and phenylthiophenyldiphenylsulfonium; and X is an anion, the counter ion of the onium salts which includes those in which X is an organic sulfonate, or metal or halogenated metalloid. Particularly useful onium salts include, but are not limited to, aryl diazonium salts, diaryl iodonium salts, and triarylsuiphonium salts. Further examples of onium salts are described in U.S. Patent No. 5,086,086, column 4, lines 29-61, and such a description is incorporated herein by reference. Cationic photoinitiators that are also useful include aromatic iodonium complex salts and aromatic sulfonium complex salts. Complex aromatic iodonium salts have the formula: r wherein Ar1 and Ar2 are aromatic groups having from 4 to 20 carbon atoms and are selected from the group consisting of phenyl, thienyl, furanyl and pyrazolyl groups; Z is selected from the group consisting of oxygen, sulfur, wherein R is aryl (having 6 to 20 carbon atoms, such as phenyl) or acyl (having 2 to 20 carbon atoms, such as acetyl, benzoyl, etc.), a carbon-carbon bond, or wherein Ri and R2 are independently selected from hydrogen, alkyl radicals of 1 to 4 carbon atoms, and alkenyl radicals of 2 to 4 carbon atoms; n is zero or 1; and X 'is a halogen-containing complex anion, selected from tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate and hexafluoroantimonate. The salt photoinitiators of the aromatic sulfonium complex are described by the formula: wherein R3, R * and R5 can be the same or different, provided that at least one such group is aromatic and such groups can be selected from the aromatic groups having from 4 to 20 carbon atoms (for example, phenyl, thienyl, furanyl substituted or unsubstituted) and alkyl radicals having from 1 to 20 carbon atoms. The term "alkyl" as used herein includes substituted and unsubstituted alkyl radicals. Preferably, R3, R4 and Rs are each aromatic groups; and Z, n and X "are as defined above .. Of aromatic suifonium complex salts that are suitable for use in the present invention, the preferred salts are triaryl-substituted salts, such as triphenyl sulfonium hexafluorophosphate and triphenylsulfonium hexafluoroantimonate. The triaryl substituted salts are preferred because they are thermally more stable than the mono- and diaryl substituted salts. The thermal free radical initiators useful in the present invention include, but are not limited to azo initiators, peroxide, persulfate and redox initiators. Suitable azo initiators include, but are not limited to, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) (VAZO ™ 33), 2,2'-azobis dihydrochloride (amidinopropane) (VAZO ™ 50 ); 2,2'-azobis (2,4-dimethylvaleronitrile) (VAZO ™ 52); 2,2'-azobis (isobutyronitrile) (VAZO ™ 64); 2,2'-azobis-2-methylbutyronitrile (VAZO ™ 67); 1,1'-azobis (1-cyclohexadecanecarbonitrile) (VAZO ™ 88), all of which are available from DuPont Chemicals and 2,2'-azobis (methyl isobutyrate) (V-601) available from Wako Chemicals. Suitable peroxide initiators include, but are not limited to, benzoyl peroxide, acetyl peroxide, lauroyl peroxide, decanoyl peroxide, dicetyl peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate (PERKADOX ™ 16S, available from AKZO Chemicals), di (2-ethylhexyl) peroxydicarbonate, t-butyl peroxypivalate (Luperson ™ 11, available from Atochem), t-butylperoxy-2-ethylhexanoate (Trigonox ™ 21-C50, available from Akzo Chemicals, Inc.) and peroxide of dicumil. Suitable persulfate initiators include, but are not limited to, potassium persulfate, sodium persulfate and ammonium persulfate. Suitable redox (oxidation-reduction) initiators include, but are not limited to, combinations of the above persulfate initiators with reducing agents such as sodium metabisulfite and sodium bisulfite; systems based on organic peroxides and tertiary amines, for example, benzoyl peroxide plus dimethylaniline; and systems based on organic hydroperoxides and transition metals, for example, eumeno hydroperoxide plus cobalt naphthenate. Other initiators include, but are not limited to, pinacols, such as tetraphenyl-1,2,2-ethanediol. Preferred thermal free radical initiators are selected from the group consisting of peroxides and azo compounds that do not contain nitrite or basic groups. The most preferred initiators are V-601, Lupersol ™ 11 and Perkadox ™ 16S, and mixtures thereof, because their preferred decomposition temperature is in the range of about 45 to 95 ° C. Additionally, they are generally inert towards initiators of cationic polymerization.

The initiator is present in a catalytically effective amount and such amounts are usually in the range of about 0.01 parts to 5 parts, and more preferably in the range of about 0.025 to 2 parts by weight, based on 100 total parts by weight of the monomer or monomer mixture. If a mixture of initiators is used, the total amount of the initiator mixture would be as if a single initiator were used. Photoinitiators that are useful for partially polymerizing the non-crosslinking alkyl acrylate monomer to prepare syrups include benzoin ethers, such as benzoin methylether or benzoin isopropyl ether, substituted benzoin ethers, such as methyl ether, anisoine, substituted acetophenones, such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone, substituted alpha-ketoles, such as 2-methyl-2-hydroxypropiophenone, aromatic sulfonyl chlorides, such as 2-naphthalene sulfonyl chloride and photoactive oximes , such as 1-phenyl-1,2-propanedione-2- (O-ethoxycarbonyl) oxime. They can be used in amounts, which when dissolved provide about 0.001 to about 0.5 weight percent of the alkyl acrylic monomer, preferably at least 0.01 percent. Optionally, monohydroxy- and polyhydroxy alcohols can be added to the curable compositions of the invention, as chain-extending agents for the epoxy resin. Suitable examples of alcohols include, but are not limited to, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, pentaerythritol, 1,2-propanediol, ethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol and glycerol. Preferably, the compounds containing hydroxyl groups, particularly compounds containing from about 2 to 50 hydroxyl groups and especially, compounds having a weight average molecular weight of from about 50 to 25,000, preferably from about 50 to 2,000, for example , polyesters, polyethers, polyethers, polyacetals, polycarbonates, poly (meth) acrylates and polyester amides, containing at least 2, in general from about 2 to 8, but preferably from about 2 to 4 hydroxyl groups or even prepolymers containing The hydroxyl of these compounds are representative compounds useful in accordance with the present invention and are described, for example, in Saunders, High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology," Vol.1, pages 32-42, 44- 54 and Vol. II, pages 5-6, 198-99 (1962, 1964), in Kunststoff-Handbuck, Vol. VII, pages 45-71 (1966). It is permissible, of course, to use mixtures of the aforementioned compounds containing at least two hydroxyl groups and having a molecular weight of about 50 to 50,000, for example, mixtures of polyethers and polyesters. In some cases, it is particularly advantageous to combine low melting point and high melting point polyhydroxyl compounds (German Offenlegungsschrift No. 2,706,297).

Low molecular weight compounds containing at least two reactive hydroxyl groups (molecular weight of about 50 to 400) suitable for use in accordance with the present invention are compounds which preferably contain hydroxyl groups and generally contain about 2 to 8, preferably from about 2 to 4 reactive hydroxyl groups. It is also possible to use mixtures of different compounds having at least two hydroxyl groups and having a molecular weight in the range of about 50 to 400. Examples of such compounds are ethylene glycol, 1,2- and 1,3-propylene glycol, , 4 and 2,3-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol, trimethylolpropane, 1,4-bis-hydroxymethylcyclohexane , 2-methyl-1,3-propanediol, dibromobutendioi (US Patent No. 3,723,392) glycerol, trimethylolpropane, 1, 2,6-hexanetriol, trimethylolethane, pentaerythritol, quinitol, mannitol, sorbitol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols, di-propylene glycol, higher polypropylene glycols, dibutylene glycol, higher polybutylene glycols , 4,4'-dihydroxydiphenyl propane and dihydroxy methylhydroquinone. Other polyols suitable for the purposes of the present invention are mixtures of hydroxy aldehydes and hydroxy ketones ("formosa") or the polyhydric alcohols obtained therefrom by reduction ("formitol"), which are formed in the self-condensation of hydrated formaldehyde in the presence of metal compounds as catalysts and compounds capable of the formation of enediol as co-catalysts (German Offenlegungsschrift patents Nos. 2,639,084, 2,714,084, 2,714,104, 2,721,186, 2,738,154 and 2,738,512). It is contemplated that polyfunctional alcohols such as poly (ethylene glycol) carboceras, poly (ethylene glycol methyl ether), poly (ethylene glycol), tetrahydrofurfuryl ether, poly (propylene glycol) may also be used in the compositions of the present invention. It is also within the scope of this invention to add optional adjuvants provided they are not detrimental to cationic cure, and include, for example, thixotropic agents; plasticizers; hardening agents, such as those shown in U.S. Patent No. 4,846,905, pigments; fillings; abrasive granules, stabilizers, light stabilizers, antioxidants, flow agents, bulking agents, opacifying products (varnishes), dyes, binders, blowing agents, fungicides, bactericides, surfactants; glass and ceramic beads; and reinforcing materials, such as woven and non-woven fabrics of organic and inorganic fibers, such as polyester fibers, glass polyimide and ceramic fibers; and other additives as known to those skilled in the art can be added to the compositions of this invention. In an amount effective for its intended purpose, normally amounts of up to about 25 parts of adjuvant per total formulation weight can be used. The additives can modify the properties of the basic composition to obtain a desired effect. In addition, the additives can be reactive components such as materials containing reactive hydroxyl functionality. Alternatively, the additives may also be substantially non-reactive, such as fillers, in which inorganic and organic fillers are included. It is optionally within the scope of this invention to include photosensitizers or photoaccelerators in the radiation sensitive compositions. The use of the photosensitizers or photoaccelerators alters the wavelength sensitivity of the radiation sensitive compositions employing the latent catalysts of this invention. This is particularly advantageous when the incident radiation is not strongly absorbed by the latent catalyst. The use of a photosensitizer or photoaccelerator increases the sensitivity to radiation, to allow shorter exposure times and / or the use of less powerful radiation sources. Any photosensitizer or photoaccelerator can be useful if your triplet energy is at least 45 kilocalories per mole. Examples of such photosensitizers are given in Table 2-1 of the reference, SL Murov, Handbook of Photochemisty, Marcel Dekker Inc., NY, 27-35 (1973) and include pyrene, fluoranthene, xanthone, thioxanthone, benzophenone, acetophenone, benzyl, benzoin and ethers of benzoin, ensen, p-terrynyl, acenaphthene, naphthalene, phenanthrene, biphenyl, substituted derivatives of the preceding compounds and the like. When present, the amount of the photosensitizer or photoaccelerator used in the practice of the present invention is generally in the range of 0.01 to 10 parts, and preferably 0.1 to 1.0 parts by weight of the photosensitizer or photoaccelerator by the organometallic salt. or salt of onium.

Glass microbubbles having an average diameter of 10 to 200 microns can be combined with the polymerizable compositions of this invention, as taught in U.S. Patent No. 4,223,067. If the microbubbles comprise from 20 to 65 volume percent of the pressure sensitive adhesive, the polymerized product will have a foam-like appearance and be suitable for uses for which foam-reinforced pressure-sensitive adhesive tapes are useful. Electrically conductive particles, as taught in U.S. Patent No. 4,606,962 can be combined with the polymerizable compositions of this invention. Conductive particles, such as solid metal particles, carbon black, metal coated particles or metal flakes, added to the polymerizable compositions of this invention can provide electrical conduction between the semiconductor chips and the circuit traces. Advantageously, such a conductive adhesive layer eliminates welding and provides better mechanical strength. In addition, more connections can be made per area (clear) when using a conductive adhesive. The removal of solder is safer from the environmental point of view, since dangerous solvents and solder lead are eliminated. In addition, thermally conductive particles, such as metal oxide particles can be combined with the polymerizable compositions of the present invention. Other materials that may be combined with the polymerizable compositions of this invention include tackifying agents, reinforcing agents and other modifiers, some of which may be copolymerized with the cationically or free radical polymerizable monomers or independently photopolymerized. However, the addition of any such material adds complexity and from here, expense to an otherwise simple, direct and economic process and is not preferred, except that they are used to obtain specific results. While it is preferred that the solvents are not used in the preparation of the polymerizable compositions of the present invention, the solvents, preferably organic, can be used to assist in the dissolution of the catalyst system in the free radical and cationically polymerizable monomers. . It may be advantageous to prepare a concentrated solution of the organometallic complex salt or the onium salt in a solvent to simplify the preparation of the polymerizable composition. Representative solvents include acetone, methyl ethyl ketone, cyclopentanone, methyl cellosolve acetate, methylene chloride, nitromethane, methyl formate, gamma-butyrolactone, propylene carbonate and 1,2-dimethoxyethane (glime). The irradiation sources that provide light in the region of 200 to 800 nm are effective in the practice of this invention. A preferred region is between 250 to 700 nm. Suitable sources of radiation include mercury discharge vapor lamps, carbon arcs, halogen quartz lamps, tungsten lamps, xenon lamps, fluorescent lamps, lasers, sunlight, etc. The amount of exposure required to effect the polymerization is dependent on such factors as the identity and concentrations of the photoactivatable catalyst system, the free-radical and cationically-specific polymerizable monomers, the thickness of the exposed material, the type of the substrate, the intensity of the source of radiation and the amount of heat associated with radiation. The preferred composition of the invention comprises monomeric ratios of 10-70, preferably 20-50% of epoxy monomer (s) and 30-90%, preferably 50-80% of acrylate monomer (s).

Partially prepolymerized syrups The curable adhesive composition can be prepared by using a free radical polymerizable syrup (also referred to as "syrup"), which consists of partially polymerized free radical monomers (1% to 30% conversion) or a mixture of partially polymerized free radical monomers and substantially unpolymerized epoxy monomers and optional adjuvants.

Method 1 A first step in the preparation of a syrup is to mix the free radical polymerizable monomers with a catalytically effective amount of a free radical initiator, preferably a free radical photoinitiator. Preferably, the free radical photoinitiator is not a crosslinking agent and is generally present in an amount within the range of 0.0001 to 5.0% by weight of the polymerizable composition, preferably in the range of 0.01 to 1.0% by weight of the polymerizable composition. A second step, which is simultaneous and concurrent with step (3) is to purge the system (the polymerizable composition, also as the reaction environment), for example, by bubbling an inert gas, such as N2, Ar, or He through the polymerizable composition to remove any residual oxygen. A third step is to apply energy to the free radical polymerizable composition to allow it to polymerize, such that the viscosity increases to a viscosity within a range of 0.3 to 20.0 Pascal seconds at room temperature. Preferably, the viscosity after this step is in the range of 500 to 4000 cps (0.5 to 4.0 Pa-s). The increased viscosity provides a syrup that is more suitable as a coating composition for the production of the articles of the invention. The polymerizable composition can be polymerized using any well known free radical polymerization technique and air cooled to the desired viscosity. Preferably, the free radical initiator is a photoinitiator and the partial polymerization can be stopped at any point by eliminating the source of irradiation. A fourth step is to mix the cationically polymerizable monomers and the optional alcohol-containing material to the syrup. A fifth step is to mix at least one organometallic complex or onium salt and at least one additional free radical initiator to the syrup of step three. The additional free radical initiator may be the same as the initiator of step 1 or different. Optically birective, free radical polymerizable monomers, bifunctional monomers, adjuvants to the syrup can be optionally added at this time. A sixth step is to degas the curable compositions under vacuum to eliminate bubbles, volatile solvents, dissolved air, oxygen and the like. Although it is preferable to do this stage before coating, it can be carried out at any time from a few hours to several weeks before coating. To ensure the stability of degassed curable compositions, it is preferable to keep them away from exposure to unwanted light.

Method 2 A first step in this alternative preparation for a syrup is to mix the polymerizable monomers (cationically and free radical polymerizable monomers) with a catalytically effective amount of at least one free radical initiator. Preferably, the free radical initiator is not a crosslinking agent and is generally present in an amount within the range of 0.001 to 5.0% by weight of the polymerizable composition, preferably in the range of 0.01 to 1.0% by weight of the polymerizable composition.

A second stage, which is simultaneous and concurrent with the stage (3) is to purge the system (the polymerizable composition, also as the reaction environment), for example, by bubbling an inert gas, such as N2, Ar or He has, through the polymerizable composition to remove any residual oxygen. A third step is to apply energy to the polymerizable composition to allow the free radical polymerizable monomers to polymerize, such that the viscosity increases to a viscosity within the range of 0.3 to 20.0 Pascal seconds (Pa-s) at room temperature . Preferably, the viscosity after this stage is in the range of 0.5 to 2.0 Pa-s. The increased viscosity provides a syrup that is more suitable as a coating composition for the production of the articles of the invention. The polymerizable composition can be polymerized by using any well known free radical polymerization technique and cooling with air to achieve the desired viscosity. A fourth step is to mix at least one complex or salt of onium, and at least one additional free radical polymer, any optional birereactive free radical polymerizable monomer, bifunctional monomer, syrup adjuvants of step two. A fifth step is to degas the curable compositions under vacuum to eliminate bubbles, dissolved air, volatile solvents, oxygen and the like. Although it is preferable to perform this step just before coating, it can be carried out at any time from a few hours to several weeks before coating. To ensure the stability of degassed curable compositions, it is preferable to keep them away from unwanted light exposure. Once the curable adhesive compositions have been prepared using either method 1 or method 2, the compositions can be coated on a carrier fabric and polymerized to produce a curable pressure sensitive adhesive having an improved shelf life, in such a way that the pressure-sensitive adhesive properties are retained for a longer period of time than the known curable epoxy-acrylate adhesives of the prior art.

Thermal processing The thermally initiated free radical polymerizations of the invention are carried out by using a single heating zone in the polymerization zone or multiple heating zones in the polymerization zone. The curable adhesive composition can be coated via a coating station on at least one main surface of a carrier fabric. In many situations, it may be desirable to coat it between a lower carrier fabric and a higher carrier fabric. Once coated, the curable adhesive composition is processed through at least one polymerization zone, wherein the curable adhesive composition is thermally polymerized by heating it within a thermal buffer having a heat transfer process characterized by a heat transfer coefficient of at least 25 W / (m2-K) at a temperature sufficient to initiate thermal polymerization for a period of time sufficient to effect the conversion of about 5-100% of the polymerizable monomer mixture by Free radicals or syrup prepolymerized to the polymer. When the process is carried out in a heating zone, it is preferred that the time and temperature be such that at least 90% of the monomeric free radical polymerizable mixture or the prepolymerized syrup is converted to the polymer. Furthermore, it is advantageous if the heat transfer coefficient for the heat transfer process inside the thermal buffer is relatively high, preferably 100 W / (m2-K) and more preferably at least 500 W / (m2-). K). The thermal control of the polymerization process of the present invention can be stated as follows. As the polymerization occurs through the cross section of the polymerization mixture, the remainder of energy in a small unit volume of the polymerizable mixture contains components that are related to the generation of internal heat created by the polymerization reaction and on the heat transfer by conduction in and out of the small unit volume, from the surrounding unit volumes. The speed of the heat flow out of a unit volume must be fast enough to prevent an excessive temperature rise within the unit volume caused by the exothermic reaction.

If more than one heating zone is used, the first heating zone of the polymerization zone can also perform as 5% conversion of the monomeric mixture polymerizable by free radicals. Preferably, the multistage process (that is, the use of one or more of a heating zone or the combination of a pre-heating zone and at least one heating zone) is carried out continuously, this is, online, without interruption of the polymerization process. The coated mixture is heated to a first temperature and maintained for a first period of time and then immediately moved to a second heating zone without interruption of the process between the heating zones. There may also be a preheating zone, wherein the coated mixture is heated to a point just prior to the start of the polymerization of the monomeric component (s) polymerizable by free radicals. When more than one heating zone is used, the temperature of the second heating zone is generally higher than that of the first heating zone. It is within the scope of the present invention to use more than two heating zones. When each zone subsequent to the first heating zone is used to initiate the thermal initiators, the temperature of each subsequent zone is higher than the previous zone. When a single coated carrier fabric is used to prepare the pressure sensitive adhesives of the invention, the polymerization is carried out in such a way that the oxygen is essentially excluded from the polymerization zone. However, when the monomeric free radical polymerizable mixture or the monomeric free radical polymerizable mixture is partially coated between two carrier fabrics, it is not generally necessary to exclude oxygen from the polymerization zone. The process of heat transfer within the thermal buffer may include, but is not limited to, air, helium, or forced or driven hydrogen; heat transfer via conduction, such as a metal plate, heated metal rollers; or via convection transfer to liquids, such as water, perfluorinated liquids, glycerin or propylene glycol. Heat transfer processes that are characterized as having heat transfer coefficients of at least 25 W / (m2-K) are considered to be within the scope of the present invention. Additionally, it is also within the scope of the present invention to add low molecular weight organic salts or compounds to a fluid heat transfer medium to alter the characteristics of the thermal buffer, such as providing a reduced oxygen content, the solubility of the monomers and the like. It should be noted that it is not necessary inside the thermal shock absorber to surround the coated construction with the heat transfer medium; the contact one side of the carrier fabric, or polymerization mixture may be sufficient. In addition, physical properties, such as the boiling point of the heat transfer fluid, must be taken into consideration when designing a thermal buffer, together with the type and concentration of the initiator, the processing temperature and the like.

The curable adhesive tapes of the present invention, such as transfer opaque strips, microstructured, foamed and / or opaque, can be prepared as stacked layers and / or in multiple layers, wherein more than one layer of polymerizable compositions are coated between more than one solid sheet material, then they are passed to at least one heating zone to effect all polymerization of all the layers. This is an advantage over the photopolymerizable systems, where the polymerization radiation can have difficulty to reach all the layers of the construction equally. A further advantage is that two or more different internal coating materials can be used simultaneously in order to improve the efficiency and performance of the tape production facilities. As will be appreciated by those skilled in the art, such a coating material may have a low adhesion surface (s) and may be removed after the polymerization is consumed or one such surface may be a tape reinforcement material. which remains permanently fixed to the curable adhesive product. It is also contemplated that multiple coating stations may be positioned in series or in parallel upstream of the polymerization zone. This can be carried out with or without the use of multiple top carrier fabrics. A stacked tape configuration is also within the scope of the present invention. For example, a four layer ply tape having a lower coating and three coatings separating four coated layers of polymerizable composition of the invention can be constructed by using multiple coating stations. Optionally, an upper layer (eg, fifth layer) is within the scope of the invention, when it is desired, for example, to exclude oxygen from the upper coated layer. In addition, it will be appreciated that a four-layer configuration is only a single contemplated configuration. For example, the number of layers should not be interpreted limited to four and can be two or more, the coatings used can be different materials, the curable syrup can be for each or even in multilayers between coating layer. A multi-layer tape configuration is also within the scope of the present invention, wherein two or more layers can be coated on top of each other on a single coating. Optionally, such multilayer can be part of a stacked configuration, as previously described. Cured coated constructions can be post-treated or post-conditioned, that is, treated further after the polymerization of the free-radical polymerizable component (s), but before the component is cured? cationically cured Such treatments may be useful, for example, to minimize monomeric debris, increase the cut resistance, corona treat the coating and provide crosslinking. Post-treatment techniques commonly involve a source of energy, such as microwave radiation, electron beam, IR, electromagnetic radiation, radiant heat, forced air, driven air, metal plates and heated metal rolls. It will be appreciated that any post-treatment or conditioning process commonly used by those skilled in the art for treating tapes, films and the like can be used in combination with the present invention. The thermally initiated free radical polymerizations of the invention can also be carried out in an extrusion apparatus.

See, for example, U.S. Patent No. 4,619,979, the content of which is incorporated herein by reference for a detailed description of free radical polymerizations in an extrusion apparatus. Polymerizations in extrusion apparatusAlso known as "reactive extrusions" are similar to bulk polymerizations, but overcome the disadvantages of poor mixing and poor heat transfer in the viscous reaction mass and loss of control over the molecular weight distribution in the resulting polymer. An extrusion apparatus is characterized by being a wiped surface reactor, comprising a cover or container which contains at least one rotor having a rinsing portion located close to the inner surface of the cover, and a root portion. , which is substantially spaced beyond the cover of the rinsing portion. As the rotor is rotated, the rinse portion passes sufficiently close to the inner surface of the cover to clean the surface and form a seal when the reactor contains monomer and / or polymer, but not so close as to cause the Permanent deformation of either the rotor or the cover. It is necessary that the root surface of the rotor is also rinsed or cleaned continuously during the operation of the reactor.

Constant screw double screw extruders can be used as wiped surface reactors. Although double-screw, co-rotating extrusion apparatus can be used, double counter-rotating screw extrusion apparatuses are preferred. The counter-rotating extrusion apparatus acts as a positive displacement pump that transports the reaction current and also behaves as a series of small mixing zones or continuous stirred tank reactors. The double-screw counter-rotating extrusion apparatus also gives good control over the reaction temperature to give the required control over the molecular weight of the polymer and the molecular weight distribution. Polymerization in an extrusion apparatus can be easily carried out in an oxygen-free manner, since the extrusion apparatus itself is sealed and all reagents can be easily purged of oxygen and stored in an inert atmosphere, before being pumped. to the extrusion apparatus. Thus, the polymerization is carried out in a sufficiently oxygen-free atmosphere, so that no serious inhibition of free-radical polymerization occurs. When the monomer mixture is converted to the polymer and transported to the end of the extrusion apparatus, it can conveniently be extruded or coated directly onto an appropriate substrate (eg, tape reinforcement or inner coating), since there is no solvent or media. reaction to be evaporated. When the reaction mixture leaves the extrusion apparatus and is exposed to air, the polymerization is stopped. The coated pressure sensitive adhesive (PSA) of the invention thus obtained can be stored for an extended period before its final use. In use, the double counter-rotating extrusion apparatus is divided into a variety of sections having controllable screw configurations of the extrusion apparatus and the barrel. Thus, the screws of the extrusion apparatus can be composed of a variety of separate sections which can be adjusted on a common drive shaft by means of a keyhole and which can be disassembled and rearranged in various orders and orientations. For example, the screw may have one clear in the inlet section, another clear in the middle part of the length of the screw and still another clear one towards the exit end of the extrusion apparatus or, as most of the sections of the screw can be oriented to transport the reaction mass towards the outlet of the extrusion apparatus, some sections can be inverted to increase residence time and mixing. Finally, the sections of the barrel can be configured as either heating or cooling sections. The residence time and the distribution of the time necessary to consummate the reaction in general, in a top-run reactor, is controlled by the geometry, the rotational direction and the rotational speed of the screws of the extrusion apparatus. Typical residence times for the production of the pressure sensitive adhesives of the present invention are in the range of 5 minutes to 15 minutes.

In practice, a monomer mixture or prepolymer as described in method one or method two, above, is prepared in a premix tank or holding tank, where it is degassed and covered with a layer of inert gas such as nitrogen. From the holding tank, it can optionally be pumped to a static mixer, where it can optionally be preheated to a temperature in the range of 35 ° C to 55 ° C, then it is introduced at the entrance of the surface-run reactor at a sufficient pressure to maintain the stability of the process. After an appropriate residence time, the resulting polymeric material is withdrawn from the reactor and directed to a coating apparatus or otherwise packaged. In another aspect of this invention, a mixture of the polymer polymerized by free radicals, cationically polymerizable monomer and catalyst system can be combined in the molten state. A mixture is formed in the molten state, by heating the mixture to at least the softening temperature of the polymer polymerized by free radicals, usually between about 100 ° C and 150 ° C, with mechanical stirring to produce a homogeneous mixture. During the melt blending process, the polymer polymerized by free radicals, cationically polymerizable monomer and catalyst system are mixed, such as in the mixing barrel of a single screw or twin screw extrusion apparatus, where the mixture it is heated during mixing in the absence of actinic radiation that would activate the catalyst. See, for example, "Polymer Extrusion" by Chris Rauwendaal, ed. Hanser Publishers, 1986, pages 322-330, for a detailed description of mixing in screw extrusion apparatus. The polymer polymerized by free radicals, the cationically polymerizable monomer and the catalyst system are combined in a molten mixing apparatus where they are heated and combined in the molten state to form a homogeneous mixture. After an appropriate residence time, the resulting polymer material is removed from the mixer in the molten state and directed to a coating apparatus or otherwise packaged and cooled. Free radical polymerized polymers can be prepared from any of a variety of means known in the art, such as photopolymerization or thermal polymerization, any of which can be carried out in volume (100% solids) or in solution . If the polymerization is carried out in solution, the solvent must be removed before the combination in the molten state. Preferably, the (meth) acrylate polymer is prepared by photopolymerization in the volume with the cationically polymerizable monomer present. The curable pressure sensitive adhesive compositions of the present invention are useful for coatings, foams, shaped articles, adhesives, filled or reinforced composites, abrasives, caulking and sealing compounds, casting and molding compounds, filler and encapsulation compounds. , impregnation and coating compounds and other applications, which are known to those skilled in the art. The present process can be used to make many different types of ribbons. Various reinforcements and flexible coatings (also referred to as "substrates") can be used, which include films (transparent and non-transparent), fabrics, papers, fibrous non-woven constructions, metal foils, aligned filaments and the like. The reinforcements and coatings are chosen to be compatible with the processing parameters of the present invention. For example, an untreated paper coating may not be the reinforcement or coating of choice when a fluid heat exchange medium such as water is used. The polymerizable mixture or prepolymerized syrup can be coated on any suitable substrate, using coating techniques known to those skilled in the art. In addition, the polymerizable mixture can be coated on a moving substrate that does not become part of the finished article, to produce a free standing sheet or film. The compositions are commonly coated at a dry thickness ranging from 0.025 to 5.0 mm. After curable pressure sensitive adhesive compositions have been made to an article, such as transfer tape or film, the articles must be stored in the absence of actinic radiation, which is capable of activating the catalyst system.

To convert the curable pressure sensitive adhesive to a structural or semi-structural adhesive, the curable, pressure sensitive adhesive is irradiated. The sources of irradiation that provide light in the region of 200 to 800 nm are effective in the practice of this invention. A preferred region is between 250 to 700 nm. Suitable sources of radiation include mercury vapor discharge lamps, carbon arcs, tungsten lamps, xenon lamps, fluorescent lamps, lasers, sunlight, etc. The amount of exposure required to effect polymerization is dependent on such factors as the identity and concentrations of the photoinitiated catalyst system, the free-radical and cationically-specific polymerizable monomers, the thickness of the exposed material, the type of the substrate, the intensity of the source of radiation and the amount of heat, associated with radiation. Optionally, the photoactivated adhesive (that is, the structural or semi-structural adhesive) can be heat treated to complete the conversion. Suitable sources of heat for curing the thermosetting (epoxy) compositions of the invention include induction heating coils, ovens, hot plates, hot air guns, IR sources including lasers, microwave sources, etc. Objects and advantages of this invention are further illustrated by the following examples, but the particular materials and properties thereof cited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention. All materials are commercially available, for example, from Aldrich Chemical Company or for those known in the art, unless stated otherwise or are obvious.

Glossary Bulbs 350BL fluorescent bulbs available from Sylvania Corp., under the trade designation F15T8 / 350BL CpFeXyl SbF6 hexafluoroantimonate (eta6-xylenes (mixed isomers)) (eta5-cyclopentadienyl) iron (1 +) EPON 1001F diglycidyl ether bisphenol A (weight epoxy equivalent = 525.550 g / eq.) (available from Shell Chemical Co.) EPON 828 diglycidyl ether of bisphenol A (epoxy equivalent weight = 185- 192 g / eq.) (available from Shell Chemical Co.) ERL-4206 dioxide vinylcyclohexene (available as BAKELITE ERL-4206 from Union Carbide Corp.) ERL-4221 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (available as BAKELITE ERL-4221 from Union Carbide Corp.) ESACURE KB-1 2,2 -dimethoxy-2-phenylacetophenone (available from Sartomer Chemicals) IBA isobutyl acrylate nBA n-butyl acrylate PERKADOX 16 di (4-t-butylcyclohexyl) peroxydicarbonate (available from Akzo Chemicals, Inc.) POEA phenoxyethyl acrylate Super bulbs fluorescent bulbs , available from Philips Lighting, under Actinic the commercial designation TLD15W / 03 tBOX di-t-butyl oxalate (available from Aldrich Chemical Company) THFA tetrahydrofurfuryl acrylate UVI-6974 salts of triaryl sulfonium hexafluoroantimonate 50% mixed in propylene carbonate (available as CYRACURE UVI-6974 by Union Carbide Corp.) V-601 2,2'-azobisisobutyrate dimethyl (available from Wako Chemical Co.) EXAMPLES Test Methods Differential Scanning Calorimetry (DSC): Differential scanning calorimetry was used to measure the exothermic heat of reaction (Joule / gram (J / g)) associated with the curing of the cationically polymerizable monomer. The exothermic profile, that is, the maximum temperature, starting temperature, etc., of the exothermic reaction provides information regarding the conditions that were necessary to cure the material. The DSC samples were typically 6 to 12 milligrams and were operated on sealed trays in a Seiko Instruments DSC 220C at a heating rate of 10 ° C / minute. The starting temperature (Tjnicio) is the point of intersection between the tangents traced to the curve along the reference line and after the start of the exothermic reaction at the point of the maximum change in slope. The integrated energy under the exothermic maximum is related to the extent of curing. For a stable composition, more than the exothermic reaction should remain over time, which indicates that the composition is not healing prematurely. For a stable composition, the energy exothermically will decrease more rapidly over time, indicating that the composition has undergone some degree of premature curing.

Photodifferential scanning calorimetry (PDSC) The photodifferential scanning calorimetry was used to measure the exothermic heat of reaction (Joule / gram (J / g)) associated with the curing of the cationically polymerizable monomer after exposure to light. The PDSC samples were typically 6-12 milligrams and were operated on open trays in a Seiko Instruments PDC121 apparatus at a heating rate of 10 ° C / minute, after a photolysis step, using a mercury lamp. 200 watts xenon. The analysis of the exothermic profile was carried out in the same manner as described under the description of the DSC.

Shear strength of superposition Samples were prepared by cutting 12.7 mm X 25.4 mm models from the adhesive film. The internal silicone release liner was removed from one side of the model, and the exposed adhesive was applied to one end of an aluminum test sample measuring 1.7 mm x 25.4 mm x 50.8 mm. The internal silicone release liner was separated from the other side of the sample and another identical aluminum sample was placed on the adhesive, such that there was a 12.7 mm overlap of the samples and with the uncoated ends of the samples aligned in opposite directions to each other. The samples were held together and thermally cured. The prepared samples were chilled for at least 1 hour at about 22 ° C before testing. The bending shear stress was determined with the use of an Instron model 1122 tensile tester according to the test method of ASTM D1002-72 with a transverse velocity of 5 cm / minute. The bending shear stress is reported in MegaPascals (MPa).

Adhesion to 180 ° detachment Peel adhesion samples were prepared by applying a 12.7 mm wide strip of PSA tape to a desired panel (either 1.7 mm thick by 50 mm x 125 mm aluminum or microscope slides glass, standard 25 mm x 75 mm). The value of adhesion to the average release was determined by folding one end of the adhesive tape on itself at 180 °, and by measuring the force required to detach the tape from the substrate at a rate of 30.5 cm / minute when using an apparatus of Instron tensile tests model 1122. The values of the adhesion to the detachment at 180 °, are reported in Newton / centimeters (N / cm). Additional details of this test are shown in "Test Methods for Pressure Sensitive Tapes," available from the "Specification and Technical Committee of the Pressure Sensitive Tape Council," 5700 Old Orchard Road, First Floor, Skokie, IL 60077, under the PSTC test designation. -1.

Example 1: reactive extrusion of poly (acrylate) A mixture of 60 parts of a 75:25 ratio of phenoxyethyl acrylate: isobornyl acrylate, 40 parts of a 75:25 ratio of EPON ™ 828: EPON ™ 1001F, 3.8 parts of a 1: 1 ratio of cyclohexane dimethanol: 1,6-hexanediol, 1.2 parts of Wako V-601 ™ (25 weight percent in propylene carbonate), and 1.6 parts of CpFeXyl SbF6 (25 percent by weight in propylene carbonate) was metered into the throat of a 18 mm double counter-rotating extrusion apparatus by means of a peristaltic pump. The sample was transported by the length of the extrusion apparatus, subjected to operation at a screw speed of 50 rpm, through 8 heated zones (72, 81, 92, 96, 105, 110, 115 and 120 ° C, respectively ), which leave the extrusion apparatus at 120 ° C as a viscoelastic foam mass, of relatively low viscosity. The DSC analysis of material cooled to room temperature indicates a maximum exothermic temperature of 229.9 ° C and an exothermic curing curve of 74.6 J / g. The DSC photo analysis showed a maximum exothermic temperature shift at 105.2 ° C and an increase in curing exotherm at 173 J / g after a two minute photolysis step. After 429 days of storage in the dark of room temperature, the DSC photo of the sample gave a maximum exothermic temperature of 110.3 ° C and a curing exotherm of 171 J / g. This example shows that the PSA prepared by reactive extrusion has a very long storage life, essentially without advancing the epoxy resin during a period of 14 months. Adhesive tapes were prepared by pressing this polymeric material to a thickness of 0.200 mm between a film of poly (ethylene terephthalate) of 0.036 mm and poly (ethylene terephthalate) film coated with silicone of 0.100 mm, when using a plate press heated to a temperature of 170 ° C. After cooling to room temperature, these tapes were tested for adhesion to 180 ° detachment to glass and aluminum substrates with and without cure. The curing was carried out by exposing the previously prepared panels to irradiation under Super Actinic ™ bulbs for 5 minutes and then heating in an oven at 100 ° C for 10 minutes. The resulting release values are summarized below.

Adhesion to average release (N / cm wide) Sample Glass Aluminum Before curing 0.97 10.3 After curing failure of reinforcement * failure of reinforcement * * It was determined that the reinforcement of poly (ethylene terephthalate) film of 0.36 mm has a breaking strength of 31.3 N / cm in width, which indicates that adhesion to detachment greater than this value had developed as a result of curing.

Example 2: Storage life of a coated sample prepared by thermal polymerization A mixture of 30 parts of phenoxyethyl acrylate, 30 parts of isobornyl acrylate, 40 parts of epoxy monomer ERL-4221 ™ and 0.01 parts of photoinitiator KB-1 was prepared and purged with nitrogen and irradiated with 350BL fluorescent bulbs with stirring, until the viscosity of the mixture was adequate for the coating (approximately 1055 KPa). A mixture of 100 parts of the above syrup, 0.4 parts of milled CpFeXyl SbF6, 0.8 parts of methyl ethyl ketone, 0.1 parts of hexanediol diacrylate, 0.1 parts of initiator V601, 0.075 parts of PERKADOX ™ 16 initiator and 4.0 parts of a mixture of 1: 1 of 1,4-cyclohexanedimethanol: 1,6-hexanediol was degassed and covered by 0.125 mm thick spatula between two white poly (ethylene terephthalate) films, coated with 0.050 mm silicone under diffuse illumination. The sandwich construction was placed on an aluminum plate heated at 90 ° C for 15 minutes, then cooled to room temperature. The DSC analysis of the cured acrylate film, in the absence of a photopolymerization step, showed an exothermic reaction start temperature of 210.4 ° C, a maximum exothermic temperature of 226.8 ° C and a curing exotherm of 45.2 J / g. The DSC photo of the sample showed an exothermic reaction start temperature of 77.9 ° C, a maximum exothermic temperature at 94.6 ° C and a curing exotherm of 204.7 J / g after a five minute photolysis step. The exothermic curing energy was verified as a function of time in diffuse illumination at room temperature to determine the stability during the storage of the samples. The exothermic curing energy measured after a photolysis step is summarized below.

Table 1 Days at temperature Curing energy Ambient appearance (J / g) 0 204.7 transparent, adherent PSA 29 188.7 transparent, adherent PSA 44 185.9 transparent, adherent PSA 89 174.1 transparent, adherent PSA 139 171.1 transparent, adherent PSA 217 195.3 transparent, Adhesive PSA 258 193.9 transparent, adhesive PSA 332 202.1 transparent, PSA adherent 391 186.3 transparent, PSA adherent 398 213.3 transparent, PSA adherent 422 187.9 transparent, PSA adherent This example demonstrates that no advancement of the epoxy monomer had taken place after 14 months of storage at room temperature and that the PSA had excellent shelf life after thermal polymerization.

Examples 3-6 v 1C to 4C: Light-curing of the acrylate against thermal polymerization A cohesive acrylate syrup was made, which contained 60 parts by weight of nBA and 40 parts by weight of THFA. 0.04 parts by weight of the KB-1 photoinitiator was added to the acrylate mixture, the mixture was purged with nitrogen bubbling and the acrylate monomers were taken at approximately 10% polymerization conversion by irradiation with 350BL fluorescent bulbs. 60 parts by weight of this syrup were mixed with 40 parts by weight of an epoxy mixture consisting of 80 parts by weight of Epon 828 and 20 parts by weight of Epon 1001F. Eight different formulations were prepared from this epoxy / acrylic mixture consisting of the components and the amounts summarized in Table 2 (all amounts are parts by weight). Table 2 Component C1 C2 C3 C4 3 4 5 6 Mixture of Epoxy / 100 100 100 100 100 100 100 100 Acrylate - 4.0 - 4.0 - 4.0 - 4.0 Cyclohexane dimethanol t-BOX - - 0.4 0.4 - - 0.4 0.4 KB-1 0.6 0.6 0.6 0.6 - - - - CpFeXylSbF6 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 V-601 - _. _ 0.1 0.1 0.1 0.1 Perkadox P-16 - - - - 0.15 0.15 0.15 0.15 Prior to coating, each of the formulations was de-aerated in a vacuum chamber, then covered by a spatula to a thickness of 0.75 mm between two transparent polyethylene terephthalate release liners of 0.100 mm. Samples C1 to C4 were irradiated for 13 minutes with 350BL fluorescent bulbs at a light dosage of 1960 mJ / cm2. These films were self-supporting, adherent, transparent pressure sensitive adhesives. Samples 3 to 5 were immersed in water at 83 ° C for 15 minutes, followed by 10 minutes in an oven at 100 ° C. These films were also pressure sensitive, self-supporting, adherent, transparent adhesives. Samples of these adhesives were used to adhere aluminum panels of 50.8 mm x 25.4 mm x 1.7 mm. Prior to adhesion, the panels were cleaned with isopropanol. Samples 3 to 5 were irradiated for 5 minutes under Super Actinium ™ bulbs before the adhesion preparation. An overlap joint of approximately 1.2 cm in length was formed and the adhered strips were placed in a circulating air oven at 100 ° C for 30 minutes. The shear bond strength of the overlap was measured by using an Instron Tensile Model # 1122 Test Apparatus. The speed of separation of the jaws was 5 cm / minute. The results are summarized in Table 3.

Table 3 Sample Adhesion Resistance Mode of Shear Failure of Adhesion Overlay (MPa) C1 4.48 Adhesive C2 6.72 Adhesive C3 6.53 Adhesive C4 7.52 Adhesive 3 1.01 Adhesive 4 1.73 Adhesive 5 7.16 Adhesive 6 5.43 Adhesive It was found that samples 3 and 4 were not fully cured. Additional overlap cut panels were prepared in the same manner as described above, with the exception that the adhered strips were placed in a circulating air oven at 120 ° C for 30 minutes. The resistance to the adhesion of cut-off of these samples was measured as described above and the results are tabulated below.

Sample Adhesion Resistance Shear Failure Mode of Adhesion Overlay (MPa) 3 3.30 Adhesive 4 5.63 Adhesive The storage stability at room temperature of these samples was verified by determining the exothermic energy of the epoxy curing by using a Seiko DSC as a function of time at room temperature. Samples 3 to 6 were irradiated for 5 minutes under Super Actinic ™ bulbs before analysis in the DSC. Samples C1 to C4 were analyzed without the photolysis step.

Table 4 Shows 2 days at T.A. 15 days at T.A. 33 days at T.A.

C1 153.1 J / g (adherent) 77.2 J / g (low adhesion) 21.2 J / g (non-adherent) C2 137 3 J / g (adherent) 47.0 J / g (low adhesion) 21.0 J / g (non-adherent) C3 149.2 J / g (adhßrßnte) 76.6 J / g (low adhesion) 30.4 J / g (non-adherent) C4 139.7 J / g (adherent) 60.6 J / g (low adhesion) 18.5 J / g (non-adherent) 3 142.0 J / g (adherent) 152.5 J / g (adherent) 158.9 J / g (adherent) 4 148.7 J / g (adherent) 146.4 J / g (adherent) 150.1 J / g (adherent) 159.8 J / g (adherent) 159.8 J / g (adherent) 166.0 J / g (adherent) 6 147.5 J / g (adherent) 157.7 J / g (adherent) 156.6 J / g (adherent) After 33 days of storage at room temperature, samples C1 to C4, those that were light-cured, cured to a significant extent and were no longer adherent or worked as pressure sensitive adhesives. Samples 3 to 6, those that were thermally polymerized, showed no signs of advancing the cure and remained adherent and continued to function as pressure sensitive adhesives.

Example 7: Latency at room temperature after photoactivation A mixture of 30 parts of phenoxyethyl acrylate, 30 parts of isobornyl acrylate, 40 parts of epoxy monomer ERL-4206 and 0.02 parts of photoinitiator KB-1 was prepared and purged with nitrogen and irradiated with 350BL fluorescent bulbs with stirring until the viscosity of the mixture was appropriate for the coating (approximately 700 KPa). A mixture of 100 parts of the above syrup, 0.4 parts of milled CpFeXyl SbF6, 0.8 parts of methyl ethyl ketone, 0.4 parts of hexanediol diacrylate, 0.1 parts of initiator V-601 and 0.15 parts of Perkadox 16 initiator was degassed and spatula coated to a thickness of 0.125 mm between two PET films coated with silicone of 0.100 mm, under diffuse lighting. The sandwich construction was placed in water at 85 ° C for 15 minutes, followed by water at 98 ° C for 10 minutes, then cooled to room temperature. The film was a self-supporting, sticky, transparent pressure sensitive adhesive. The DSC analysis of the film, after 5 minutes of irradiation with Super Actinic ™ bulbs showed a maximum exothermic temperature at 72.2 ° C and a curing exotherm of 297.1 J / g. The curing speed of this film at an isothermal temperature of 60 ° C was determined by irradiating the film for 2 minutes with Super Actinic ™ bulbs with the top coating removed, after which the coating was replaced and the sample was immersed in a silicone oil bath heated to 60 ° C for a predetermined duration of time (see Table 5). The DSC analysis was carried out on the sample after removing it from the silicone oil to determine the extent of curing.

Table 5 Minutes at 60 ° C Curing energy (J / g) Residual cure (%) 0 297.1 100.0 2 91.6 30.8 5 28.7 9.7 10 16.5 5.6 40 0.0 0.0 The curing speed of this film at room temperature was determined by irradiating the film for 2 minutes with Super Actinic ™ bulbs with the top coating removed, after which the coating was replaced and the sample was stored in the dark at room temperature. Environment (22 ° C). The DSC analysis was carried out on the sample after several time durations to determine the extent of curing.

Table 6 Minutes at temperature Cured curing energy ambient residual (22 ° C) (J / g) (%) 0 297.1 100.0 30 237.8 80.0 60 111.9 37.7 180 80.9 27.2 540 50.1 16.9 4680 36.9 12.4 These results show that the latency of curing at ambient temperatures can be achieved after a stage of irradiation in these materials to allow positioning and repositioning.

Examples 8-9: Comparison of cationic organometallic initiators and onium photoinitiators after thermal polymerization. A mixture of 45 parts of phenoxyethyl acrylate, 15 parts of isobornyl acrylate, 30 parts of EPON 828, 10 parts of EPON 1001F and 0.04 parts of KB-1 photoinitiator was prepared and purged with nitrogen and irradiated with fluorescent bulbs. 350BL with stirring, until the viscosity of the mixture was appropriate for the coating (approximately 700 KPa). A mixture of 100 parts of the above syrup, 3.8 parts of a 1: 1 mixture of 1,4-cyclohexane dimethanol: 1,6-hexanediol, 0.3 parts of initiator V-601, 0.1 parts of PERKADOX 16 initiator and the cationic photocatalyst listed in Table 7 it was degassed and covered by a spatula to a thickness of 0.200 mm between a poly (ethylene terephthalate) film of 0.036 mm and a film of poly (ethylene terephthalate) coated with silicone of 0.100 mm under diffuse illumination. The sandwich construction was placed in water at 85 ° C for 15 minutes, followed by water at 98 ° C, for 10 minutes, then cooled to room temperature. These tapes were tested for adhesion to 180 ° detachment to glass and aluminum substrates, with and without cure. The curing of the material of Example 8 was carried out by exposing the panels to irradiation under Super Actinic ™ bulbs for 5 minutes, and then heating in an oven at 100 ° C for 10 minutes. The curing of the material of Example 9 was carried out by exposing the panels to irradiation under 350BL bulbs for 5 minutes without heating step. The resulting release values are summarized in Table 7.

Table 7 Average release adhesion (N / cm wide) Aluminum glass catalyst example 8 0.4 parts Before curing 0.06 4.4 CpFeXyISbFß After curing 86.4 6.6 9 3.0 parts Before curing 0.09 3.0 UVI-6974 After curing 2.1 6.6 These results show that cationic organometallic catalysts and photoactivatable onium catalysts can be used to prepare adhesives Curable pressure sensitive, when using the thermal polymerization of the component? of acrylate. Both curable pressure sensitive adhesives demonstrated an increase in adhesion resistance after curing of the epoxy.

Examples 10-11: Comparisons of the organometallic compound and onium in curable pressure sensitive adhesives, combined in the molten state Mixture 1: A mixture of 45 parts of phenoxyethyl acrylate, 15 parts of isobornyl acrylate, 30 parts of I? PON 828 , 10 parts of EPON 1001F and 0.04 parts of photoinitiator KB-1 was prepared and purged with nitrogen and irradiated with 350BL fluorescent bulbs with stirring, until the viscosity of the mixture was appropriate for the coating (approximately 700 KPa). Mixture 2: A mixture of 100 parts of the above syrup, 3.8 parts of a 1: 1 mixture of 1,4-cyclohexane dimethanol: 1,6-hexanediol, 0.2 parts of photoinitiator KB-1 was degassed and coated at 0.75 mm thickness between two films of poly (ethylene terephthalate) coated with silicone of 0.100 mm. This double coating construction was irradiated for 15 minutes by using 350BL fluorescent bulbs at a light dosage of 2260 mJ / cm2. The polymerized mixture was used in examples 10 and 11. The coatings used to polymerize the mixture were separated before further processing with the photoactivatable catalyst of the pressure sensitive adhesive. In Example 10, a molten mixture of the polyacrylate-epoxy material with cationic photocatalyst was prepared by combining 100 parts of the polymerized mixture 2 (the coatings are pre-separated before the combination) with 3.0 parts of cationic photoinitiator UVI-6974 with stirring, in an aluminum container heated to 150 ° C. Pressure-sensitive adhesive tapes were prepared by pressing this polymeric material to a thickness of 0.250 mm between a polyethylene terephthalate film of 0.036 mm and a film of poly (ethylene terephthalate) coated with silicone of 0.100 mm. use a plate press heated to a temperature of 120 ° C. After cooling to room temperature, these tapes were tested for adhesion to 180 ° peel to the glass substrate before and after curing the epoxy component of the pressure sensitive adhesive. The curing was carried out by exposing the previously prepared panels to irradiation under 350BL bulbs for 5 minutes without a heating step. The resulting release values are summarized in Table 8 below. In Example 11, a molten mixture of the polyacrylate-epoxy material with cationic photocatalyst was prepared by combining 100 parts of the polymerized mixture 2 with 1.0 part of pre-dissolved CpFeXyISbFß cationic photoinitiator to % by weight in propylene carbonate, with stirring in an aluminum container, heated to 150CC.

Pressure-sensitive adhesive tapes were prepared by pressing this polymeric material to a thickness of 0.250 mm between a poly (ethylene terephthalate) film of 0.036 mm and a film of poly (ethylene terephthalate) coated with 0.100 mm silicone, when using a plate press heated to a temperature of 120 ° C. After cooling to room temperature, these tapes were tested for adhesion to 180 ° peel to the glass substrate before and after curing the epoxy component of the pressure sensitive adhesive. The curing was carried out by exposing the panels to irradiation under Super Actinic bulbs for 5 minutes, followed by heating in a homo at 100 ° C for 10 minutes. The resulting release values are summarized in Table 8 below.

Table 8 Example Adhesion to Average Glass Release (N / cm wide) 10 Before curing 0.4 After curing 10.5 11 Before curing 0.2 After curing 10.9 These results show how cationic organometallic catalysts and photoactivatable onium catalysts can be Use to prepare curable, pressure sensitive adhesives, when using melt blending techniques. Both of these curable pressure sensitive adhesives demonstrate an increase in adhesion resistance after curing of the epoxy. Various modifications and alterations of this invention will become apparent to those skilled in the art, without departing from the scope and principles of this invention, and it should be understood that this invention is not unduly limited to the illustrative embodiments summarized herein. All publications and patents are incorporated herein by reference to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference.

Claims (12)

1. Claims 1. A curable pressure sensitive adhesive, characterized in that it comprises: (i) at least one polymer polymerized by free radicals; (ii) at least one cationically polymerizable monomer; (iii) a photoactivatable catalyst system for the cationically polymerizable monomer, comprising at least one organometallic complex salt or at least one onium salt; and (v) optionally, a monohydric or polyhydric alcohol, wherein there is essentially no conversion of the cationically polymerizable monomer from the curable, pressure sensitive adhesive, for at least 10 days at 20 ° C, 50% relative humidity, when is stored in a manner to exclude actinic radiation, with the proviso that at least one polymer polymerized by free radicals is not a polymerization product of a monomer of the formula H2C = CHCO2-R2-O [CO (RaRb) cO) nH wherein R1, Ra and Rb are hydrogen or an alkyl group, R2 is a residual group of the organic compound, c is an integer from 4 to 8 and n is an integer greater than 0.
2. 2. A structural or semi-structural adhesive comprising the pressure sensitive adhesive according to claim 1, characterized in that the cationically polymerizable monomer has been cured.
3. 3. A method for preparing a curable pressure sensitive adhesive, characterized in that it comprises the steps of: (i) preparing a polymerizable composition, comprising a mixture of (a) at least one monomer polymerizable by free radicals, (b) by at least one thermal free radical initiator, (c) at least one cationically polymerizable monomer, (d) at least one photoactivatable catalyst system for the cationically polymerizable monomer, comprising at least one organometallic complex salt or at least one an onium salt, and (e) optionally a hydro-or polyhydric alcohol; and (ii) applying sufficient thermal energy to the mixture to effect substantially complete polymerization of the free radical polymerizable monomer.
4. 4. The method according to claim 3, characterized in that it further comprises the steps of: (a) applying sufficient irradiation to the curable pressure sensitive adhesive to activate the photoactivatable catalyst system; and (b) providing sufficient time and / or thermal energy to effect essentially complete polymerization of the cationically polymerizable monomer.
5. 5. A method for preparing a curable pressure sensitive adhesive, characterized in that it comprises the steps of: (i) preparing a first polymerizable composition, comprising a mixture of (a) at least one monomer polymerizable by free radicals, (b) at least one free radical initiator, (c) at least one cationically polymerizable monomer, and (d) optionally, a monohydric or polyhydric alcohol; (ii) applying sufficient energy to the mixture to effect the essentially complete polymerization of the free radical polymerizable monomer; (iii) mixing the polymerized composition, (a) a photoinitiated catalyst system for the cationically polymerizable monomer, comprising at least one organometallic complex salt or at least one onium salt, and (b) optionally, a monohydric alcohol or polyhydric with the proviso that at least one monomer polymerizable by free radicals is not a monomer of the formula: H2C = CHCO2-R -O [CO (RaRb) cO) nH wherein R1, Ra and Rb are hydrogen or a group alkyl, R2 is a residual group of the organic compound, c is an integer from 4 to 8 and n is an integer greater than 0.
6. 6. The method according to claim 5, characterized in that it further comprises the steps of: (a) applying sufficient irradiation to the curable pressure sensitive adhesive to activate the photoactivatable catalyst system, and (b) providing time and / or energy thermally sufficient to effect the essentially complete polymerization of the cationically polymerizable monomer.
7. 7. A method for preparing a curable pressure sensitive adhesive, characterized in that it comprises the steps of: (i) preparing a first polymerizable composition, comprising a mixture of: (a) at least one monomer polymerizable by free radicals, and (b) at least one free radical initiator, and (i) applying sufficient energy to the mixture to effect substantially complete polymerization of the free radical polymerizable monomer; (Ii) mixing to the polymerized composition, a second polymerizable composition, comprising a mixture of: (a) at least one cationically polymerizable monomer, (b) a photoinitiated catalyst system for the cationically polymerizable monomer, comprising at least an organometallic complex salt or at least one onium salt; and (c) optionally a monohydric or polyhydric alcohol with the proviso that at least one free radical polymerizable monomer is not a monomer of the formula: H2C = CHCO2-R2 -O [CO (RaRb) cO) nH wherein R1, Ra and Rb are hydrogen or an alkyl group, R2 is a residual group of the organic compound, c is an integer from 4 to 8 and n is an integer greater than 0.
8. 8. The method according to claim 7, characterized in that it further comprises the steps of: (a) applying sufficient irradiation to the curable pressure sensitive adhesive to activate the photoactivatable catalyst system, and (b) providing time and / or energy thermally sufficient to effect the essentially complete polymerization of the cationically polymerizable monomer.
9. 9. A pressure sensitive adhesive prepared according to the methods of claims 3, 5 or 7.
10. 10. The pressure sensitive adhesive, according to claim 9, characterized in that it also includes electrically or thermally conductive particles.
11. 11. A structural or semi-structural adhesive prepared according to the methods of claims 4, 6 or 8.
12. 12. The structural or semi-structural adhesive prepared according to claim 11, characterized in that it also includes electrically or thermally conductive particles.