WO1997040090A2 - Procede de reticulation de polymeres par rayonnement et compositions susceptibles d'etre reticulees sous l'effet d'un rayonnement - Google Patents

Procede de reticulation de polymeres par rayonnement et compositions susceptibles d'etre reticulees sous l'effet d'un rayonnement

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Publication number
WO1997040090A2
WO1997040090A2 PCT/US1997/006166 US9706166W WO9740090A2 WO 1997040090 A2 WO1997040090 A2 WO 1997040090A2 US 9706166 W US9706166 W US 9706166W WO 9740090 A2 WO9740090 A2 WO 9740090A2
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WO
WIPO (PCT)
Prior art keywords
radiation
polymer
crosslinking agent
polymerizable
process according
Prior art date
Application number
PCT/US1997/006166
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English (en)
Other versions
WO1997040090A3 (fr
Inventor
Peter A. Stark
Robin E. Wright
Chung I. Young
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Minnesota Mining And Manufacturing Company
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Publication date
Application filed by Minnesota Mining And Manufacturing Company filed Critical Minnesota Mining And Manufacturing Company
Priority to BR9708703A priority Critical patent/BR9708703A/pt
Priority to EP97920385A priority patent/EP0894112A2/fr
Priority to JP9538142A priority patent/JP2000509089A/ja
Publication of WO1997040090A2 publication Critical patent/WO1997040090A2/fr
Publication of WO1997040090A3 publication Critical patent/WO1997040090A3/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/28—Treatment by wave energy or particle radiation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C08F8/28—Condensation with aldehydes or ketones
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/04—Homopolymers or copolymers of esters
    • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09J133/08—Homopolymers or copolymers of acrylic acid esters
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38—Pressure-sensitive adhesives [PSA]
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2800/00—Copolymer characterised by the proportions of the comonomers expressed
    • C08F2800/20—Copolymer characterised by the proportions of the comonomers expressed as weight or mass percentages
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2810/00—Chemical modification of a polymer
    • C08F2810/20—Chemical modification of a polymer leading to a crosslinking, either explicitly or inherently
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/40—Additional features of adhesives in the form of films or foils characterized by the presence of essential components
    • C09J2301/416—Additional features of adhesives in the form of films or foils characterized by the presence of essential components use of irradiation

Definitions

  • This invention relates generally to a process for radiation crosslinking polymers and, more specifically, to a process for radiation crosslinking polymers using a monochromatic light source such as an excimer laser or lamp.
  • This invention further relates to radiation crosslinkable compositions and, more specifically, to compositions that include both a polymer having radiation-activitable crosslinking groups and non-polymerizable radiation-activitable crosslinkers.
  • Crosslinked polymers i.e., polymer networks
  • crosslinked polymers may show unique and highly desirable properties such as solvent resistance, high cohesive strength, and elastomeric character.
  • the crosslinking reaction can occur in situ during formation ofthe polymer. However, since further processing ofthe polymer is often necessary, it is more typical to start from the linear or branched polymer which is then crosslinked in the final processing step.
  • the curing or crosslinking step is typically activated by moisture, thermal energy or radiation. The latter has found widespread application, particularly using ultraviolet light as the radiation source.
  • Ultraviolet lamps are conventionally used as the ultraviolet light source for irradiating photo-treatable adhesives, coatings and the like. Most often, the lamp includes a mercury element bulb, although one or more additives may be used to accentuate a particular spectral range or output ofthe lamp.
  • the spectrum ofthe light radiated by the lamp is the spectrum ofthe mercury element or that ofthe additive-modified mercury element.
  • the spectrum produced by these lamps has radiation present over the entire, relatively wide range of 240-2000 nm. Because the radiation is distributed over the entire broad range, the lamp's output is relatively insignificant in any particular, narrow segment ofthe output spectrum. For some applications, however, it is desirable that the greatest part ofthe output radiation lie within a narrow range.
  • the broad spectral distribution associated with conventional ultraviolet light sources may require long exposure times and may result in photochemical degradation ofthe polymer, undesirable side reactions, and deteriorated surface properties from overcuring ofthe polymer surface.
  • Excimer lamps have been used in the modification and microstructuring of polymer surfaces and the photodeposition of various coatings on metal, dielectric and semiconductor surfaces. Examples of these applications can be found in Kogelschatz, Applied Surface Science. 54 (1992), 410-423, and Zhang et al., Journal of Adhesion Science and Technology. 8(10) (1994), 1179-1210.
  • European Patent Appl. EP 604738 Al (Nohr et al.) describes a method of preparing a laminate which involves coating a cationically curable adhesive composition onto the surface of a first sheet, exposing the adhesive composition to ultraviolet radiation from an excimer lamp having a narrow wavelength band within the range of about 260 to about 360 nm, and bringing the surface of a second sheet in contact with the adhesive composition-bearing surface ofthe first sheet.
  • the adhesive composition includes about 94 to about 60 percent by weight of a cycloaliphatic diepoxide, from about 1 to about 10 percent by weight of a cationic photoinitiator, and from about 5 to about 30 percent by weight of a vinyl chloride-vinyl acetate- vinyl alcohol te ⁇ olymer (based on the weight of the adhesive composition).
  • photopolymerizable groups such as acetophenones, benzophenones, benzil derivatives, benzoin derivatives, dialkoxy acetophenones, hydroxyalkyl phenones, ⁇ -acyloxime esters, ⁇ -halogen ketones, thioxanthones, fluoronone derivatives, anthraquinone derivatives, iron-arene complexes, dibenzosuberones, and Michlers ketone, are inco ⁇ orated into the contact adhesive. Due to their proximity to and inco ⁇ oration into the polymeric backbone, such crosslinkers provide efficient crosslinking when copolymerized at appropriate concentrations for the cured polymer's end-use.
  • Crosslinking of polymers containing radiation-activatable crosslinking groups can also be affected by the subsequent addition of other components, e.g., oligomeric or polymeric materials such as rheological modifiers, plasticizers, tackifying resins, etc. Adding these components dilutes the concentration ofthe inco ⁇ orated crosslinking groups, decreasing the ability of radically-active sites to combine and form crosslinks with other sites on the same or different polymer chains. Moreover, dilution reduces the number of cross-links per unit volume which may impair the performance ofthe crosslinked polymer system.
  • other components e.g., oligomeric or polymeric materials such as rheological modifiers, plasticizers, tackifying resins, etc. Adding these components dilutes the concentration ofthe inco ⁇ orated crosslinking groups, decreasing the ability of radically-active sites to combine and form crosslinks with other sites on the same or different polymer chains. Moreover, dilution reduces the number of cross-links per unit
  • the added components may diminish the performance ofthe inco ⁇ orated crosslinker by absorbing light that is needed to activate the crosslinking agent, by reacting with the activated crosslinker (if the added component contains abstractable hydrogen atoms), and/or by providing uninco ⁇ orated low molecular weight fragments to the composition. In all of these cases, the added components reduce the crosslinking efficiency ofthe crosslinking groups that have been inco ⁇ orated in the polymer.
  • non-polymerizable crosslinking agents offer some advantages over the copolymerizable crosslinking compounds. Although typically more volatile and marginally less efficient than their copolymerizable counte ⁇ arts, non- polymerizable crosslinking compounds can be added at any desired level to a variety of polymer systems, either before, during or following polymerization. Examples of non-polymerizable crosslinking agents include anthraquinone, substituted anthraquinone, multifunctional acetophenones, multifunctional benzophenones, and triazines.
  • U.S. Patent Nos. 4,391,678 and 4,330,590 (each to Nesley) describe a class of fast curing, non-polymerizable triazine photocrosslinkers which are mixed with acrylic monomers and, optionally, ethylenically unsaturated copolymerizable monomers. When the triazine-containing polymerizable mixture is exposed to UV radiation a crosslinked polyacrylate is formed. Although effective crosslinking agents for polyacrylates, triazines can evolve corrosive gases during polymerization and/or crosslinking.
  • 5,407,971 (Everaerts et al.) describes the use of radiation- activatable polyfunctional acetophenones and benzophenones as crosslinking agents for elastomeric polymers.
  • these radiation-activatable polyfunctional acetophenone and benzophenone crosslinking agents have lower volatility, increased compatibility, and decreased oxygen sensitivity, and avoid the evolution of toxic or corrosive by ⁇ products and discoloration ofthe final product.
  • WO 96/05249 discloses a syrup that can be cured to a crosslinked viscoelastomeric material.
  • a composition that is disclosed is based on a mixture of free radically polymerizable, ethylenically unsaturated monomers that includes a small amount of an ethylenically unsaturated monomer that has a radiation-sensitive hydrogen abstracting group. This mixture is then exposed to energy so as to partially polymerize the monomer mixture and form a coatable syrup. An ethylenically unsaturated monomer having a radiation-sensitive hydrogen abstracting group or a polyethylenically unsaturated monomer can then be added to the syrup. The syrup can then again be exposed to energy to obtain the final crosslinked viscoelastomeric material.
  • this invention relates generally to a process for radiation crosslinking polymers. It has been discovered that a monochromatic radiation source (e.g., an excimer lamp or an excimer laser) can be used to crosslink elastomers and thermoplastic polymers compounded with a radiation activatable crosslinking agent such as anthraquinone, substituted anthraquinone, acetophenones (ofthe multifunctional or copolymerizable type), benzophenones (ofthe multifunctional or copolymerizable type), and substituted triazines.
  • a monochromatic radiation source e.g., an excimer lamp or an excimer laser
  • a radiation activatable crosslinking agent such as anthraquinone, substituted anthraquinone, acetophenones (ofthe multifunctional or copolymerizable type), benzophenones (ofthe multifunctional or copolymerizable type), and substituted triazines.
  • crosslinking agent or group in connection with this invention is meant that the crosslinking agent or group can be activated, i.e. becomes reactive, upon exposure to radiation and in particular light such as light emitted by a high, medium or low pressure mercury vapor lamp or an excimer lamp or laser.
  • a radiation crosslinkable composition comprising: (i) a radiation crosslinkable polymer having abstractable hydrogen atoms (hereinafter also abbreviated as radiation crosslinkable polymer); and (ii) a non-polymerizable, radiation activatable crosslinking agent;
  • the radiation crosslinkable polymer may be a thermoplastic polymer such as those selected from the group consisting of polyolefins, polystyrenes, vinyl plastics, polyacrylates, polymethacrylates, poly(vinyl esters), polyamides, polycarbonates, polyketones, and copolymers comprising the polymerization product of at least one ofthe monomers from which the foregoing polymers may be derived and a copolymerizable comonomer.
  • a thermoplastic polymer such as those selected from the group consisting of polyolefins, polystyrenes, vinyl plastics, polyacrylates, polymethacrylates, poly(vinyl esters), polyamides, polycarbonates, polyketones, and copolymers comprising the polymerization product of at least one ofthe monomers from which the foregoing polymers may be derived and a copolymerizable comonomer.
  • the radiation crosslinkable polymer may be an elastomer such as those selected from the group consisting of polyurethanes, polydiorganosiloxanes, A-B-A-type block copolymers, synthetic rubber, natural rubber, ethylene-vinyl monomer polymers, poly(vinyl ethers), poly(vinyl esters), polyacrylates, polymethacrylates, and copolymers comprising the polymerization product of at least one ofthe monomers from which the foregoing polymers may be derived and a copolymerizable comonomer.
  • the radiation crosslinkable polymer exclusive ofthe crosslinking agent absorb substantially no radiation emitted by the monochromatic radiation source.
  • the monochromatic radiation source may be an excimer laser or an excimer lamp, the latter is preferred.
  • the monochromatic radiation source preferably emits radiation having a wavelength of about 270 to 370 nm, more preferably about 300 to 360 nm, and even more preferably about 300 to 340 nm.
  • the most preferred monochromatic radiation source is a XeCl excimer lamp that emits radiation having a wavelength of about 308 nm.
  • the radiation activatable crosslinking agent may be of either the polymerizable type (i.e., the crosslinking agent is copolymerized with the monomers that are polymerized to form the polymer), the non-polymerizable type (i.e., the crosslinking agent was combined with the polymer subsequent to its formation, or was combined with the monomers prior to the polymerization but without reacting with the monomers), or a combination of both types, and the monochromatic radiation source is an excimer lamp.
  • the radiation crosslinkable composition, subsequent to crosslinking may be a pressure sensitive adhesive.
  • the invention also provides for a process for making a pressure sensitive adhesive tape, the process comprising the steps of: (a) providing a flexible web suitable as a backing for a flexible pressure sensitive adhesive tape; (b) providing a radiation crosslinkable pressure sensitive adhesive composition comprising: (i) a radiation crosslinkable polymer having abstractable hydrogen atoms; and (ii) a radiation activatable crosslinking agent; (c) applying the radiation crosslinkable pressure sensitive adhesive composition to at least a portion of at least one surface of the flexible web; (d) providing an excimer lamp that can emit monochromatic radiation having a wavelength sufficient to activate the crosslinking agent and crosslink the polymer; and (e) exposing the radiation crosslinkable pressure sensitive adhesive composition to the radiation emitted by the excimer lamp for a time sufficient to crosslink the polymer and form a pressure sensitive adhesive tape.
  • this invention relates to radiation crosslinkable compositions
  • the non-polymerizable radiation activatable crosslinking agent is preferably selected from the group consisting of anthraquinone, substituted anthraquinone, multifunctional acetophenones, and multifunctional benzophenones.
  • triazines can in principle also be used as a non-polymerizable radiation activatable crosslinking agent, they are preferably not used in connection with the second aspect ofthe invention because they can evolve corrosive gases such as HCl upon activation and, may be subject to undesirable, premature activation during UV-radiation induced polymerization.
  • the polymer is a poly(meth)acrylate.
  • a polymer in the form of beads prepared by suspension polymerization in particular a poly(meth)acrylate in the form of suspension polymerized beads.
  • compositions ofthe second aspect of the invention are particularly suitable for use with a monochromatic radiation source such as an excimer lamp or laser
  • these radiation crosslinkable compositions can also be cured by other visible or ultraviolet light sources, including broader spectrum ultraviolet sources such as medium pressure mercury lamps, and the like.
  • this invention relates generally to a process for radiation crosslinking polymers and, more specifically, to a process for radiation crosslinking polymers by using a monochromatic radiation source.
  • a monochromatic radiation source is one which emits radiation over a narrow spectral range; for example, radiation having a half width of no more than about 50 nm, preferably about 5 to 15 nm. Any source of monochromatic radiation may be used in the first aspect ofthe invention, although it is preferred that the radiation source be an excimer laser or an excimer lamp.
  • Excimer lamps i.e., an incoherent and pulsed source
  • excimer lasers i.e., a coherent and pulsed source
  • Excimer lamps are more efficient than excimer lasers, which can result in reduced operating costs. Lamp systems tend to be smaller and more easily handled. It is easier to change the wavelength of the radiation emitted by a lamp than by a laser.
  • excimer lamps are more effective in delivering uniform radiation over a larger physical area than lasers.
  • An excimer source is typically identified or referred to by the wavelength at which the maximum intensity ofthe radiation occurs, a convention followed herein.
  • the wavelength ofthe monochromatic radiation should be useful for crosslinking the polymer and will generally be from about 270 to 370 nm, preferably about 300 to 360 nm, and more preferably about 300 to 340 nm. Monochromatic radiation having a wavelength of about 308 nm has been found to be particularly useful.
  • the wavelength ofthe emitted radiation is determined by the excimer source. While various inert gas-halogen mixtures are known and can be used as excimer sources, those based on xenon chloride (XeCl) are most preferred as the radiation of maximum intensity occurs at about 308 nm.
  • XeCl xenon chloride
  • the intensity ofthe light will generally be from about 5 to 20,000 mW/cm 2 , more preferably from about 10 to 10,000 mW/cm 2 , and most preferably from about 50 to 2,000 mW/cm 2 .
  • Excimer radiation sources are commercially available from Heraeus Noblelight, Hanau, Germany and have been described in various patent publications including
  • the monochromatic radiation source is used in conjunction with a radiation- crosslinkable composition that comprises and, more preferably, consists essentially of, one or more radiation crosslinkable polymers and one or more radiation activatable crosslinking agents.
  • the polymers (exclusive ofthe radiation activatable crosslinking agent) contain abstractable hydrogen atoms and absorb substantially no radiation emitted by the monochromatic radiation source.
  • absorb substantially no radiation it is meant that while a small amount of radiation (less than 10%, preferably less than 1%) may be absorbed by the polymer, it is preferred that no radiation be absorbed as any absorbed radiation reduces the efficiency ofthe system because it is not employed for crosslinking. This also prevents any undesirable photochemically-induced reactions that may compromise performance ofthe polymer if it were to absorb the monochromatic radiation.
  • the abstractable hydrogen atoms may be present in the backbone and/or the side chains ofthe polymer in an amount sufficient to allow crosslinking ofthe polymer to the desired level upon exposure ofthe crosslinking agent/polymer composition to the monochromatic radiation source.
  • hydrogen atoms are most easily abstracted from tertiary carbon atoms, allylic and benzylic groups, those hydrogens on carbon atoms in a position alpha to an oxygen or nitrogen atom (e.g., organic ethers and tertiary amines), and those carried by terminal or pendant mercapto groups.
  • the abstractable hydrogen atom-containing polymers that can be used in the first aspect ofthe invention are thermoplastic polymers and elastic polymers ("elastomers").
  • Thermoplastic polymers are macromolecular materials that can be repeatedly melted and solidified by heating and cooling throughout a characteristic temperature range without exhibiting chemical change during the transformation process.
  • useful abstractable hydrogen atom-containing thermoplastic polymers include polyolefins such as polyethylene, polypropylene, polymethylpentene, polybutylene, and ethylene-vinyl alcohol copolymers; polystyrene; vinyl plastics such as polyvinyl chloride, polyvinylidene chloride, and chlorinated polyvinyl chloride; polyacrylates and polymethacrylates having a high glass transition temperature such as po.y(methyl methacrylate); poly(vinyl esters) having a high glass transition temperature such as poly(vinyl acetate); polyamides; polycarbonates; polyimides; polyketones such as polyetheretherketone; and copolymers that are based on the polymerization of at least one ofthe monomers from which the foregoing polymers may be derived and a copoly
  • elastomers which are defined as macromolecular materials that return rapidly to their approximate initial dimensions and shape after substantial deformation by a weak stress and subsequent release of that stress as measured according to ASTM D 1456-86 ("Standard Test Method For Rubber Property-Elongation At Specific Stress").
  • Examples of abstractable hydrogen atom-containing elastomers useful in the present invention include polyurethanes; polydiorganosiloxanes (such as polydimethylsiloxanes); A-B-A type block copolymers such as styrene-isoprene-styrene block copolymers (SIS), and styrene-butadiene-styrene block copolymers (SBS); various synthetic rubbers such as ethylene-propylene-diene monomer rubbers (EPDM), styrene-butadiene rubber (SBR), polyisobutylene, synthetic polyisoprene, polybutadiene, acrylonitrile-butadiene copolymers, and polychloroprene; natural rubber; ethylene vinyl monomer polymers such as ethylene-vinyl acetate; poly( ⁇ -olefins); poly(vinyl ethers); poly(vinyl esters); polymethacrylates and
  • the preferred elastomers for use in the first aspect ofthe invention are polyacrylates, natural rubber, polybutadiene, polyisoprene, SBS block copolymers, and SIS block copolymers.
  • Most preferred as the thermoplastic or elastomeric radiation crosslinkable polymer in the radiation curable compositions ofthe invention are poly(meth)acrylates which can be obtained as the polymerization product of acrylate or methacrylate monomers, often copolymerized with ethylenically unsaturated free radically polymerizable monomers.
  • acrylate and methacrylate monomers include but are not limited to those selected from the group consisting of methyl acrylate, methyl methacrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, 4-methyI-2-pentyl acrylate, 2-methylbutyl acrylate, isoamyl acrylate, sec-butyl acrylate, n-butyl acrylate, tert-butyl acrylate, isobornyl acrylate, butyl methacrylate, ethyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate and mixtures thereof.
  • Preferred acrylate monomers include those selected from the group consisting of isooctyl acrylate, isononyl acrylate, isoamyl acrylate, isodecyl acrylate, 2- ethylhexyl acrylate, isobornyl acrylate, n-butyl acrylate, sec-butyl acrylate, and mixtures thereof.
  • Ethylenically unsaturated free radically reactive monomers which are readily copolymerizable with acrylate and methacrylate monomers can also be used in the preparation ofthe preferred polyacrylates.
  • Such monomers include but are not limited to those selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, sulfoethyl methacrylate, N- vinyl pyrrolidone, N- vinyl caprolactam, acrylamide, t-butyl acrylamide, dimethyl amino ethyl acrylamide, N-octyl acrylamide, acrylonitrile, vinyl acetate, vinyl propionate, styrene, mixtures thereof, and the like.
  • Preferred monomers include those selected from the group consisting of acrylic acid, methacrylic acid, N-vinyl pyrrolidone, styrene, vinyl acetate, and mixtures thereof.
  • Some ofthe foregoing thermoplastic polymers and elastomers may be more effectively used in the first aspect ofthe invention if the monomers from which they are derived are copolymerized with monomers from which the other ofthe thermoplastic polymers and elastomers are derived.
  • compositions used in the first aspect ofthe invention include a radiation activatable crosslinking agent ofthe copolymerizable or non-polymerizable type, although the latter are preferred.
  • radiation activatable crosslinking agents useful in the first aspect ofthe invention are those which become hydrogen abstractors after absorbing light having a wavelength of about 270 to 370 nm, preferably about 300 to 360 nm, more preferably about 300 to 340 nm.
  • Copolymerizable radiation activatable crosslinking agents generally become randomly inco ⁇ orated into the backbone ofthe radiation crosslinkable polymer during the polymerization ofthe polymer.
  • the copolymerizable crosslinking agent should preferably be compatible and miscible with the monomers from which the polymer is derived (i.e., there should be no gross phase separation upon mixing).
  • Copolymerizable crosslinking agents tend to promote more efficient crosslinking than their non- polymerizable counte ⁇ arts and minimize concerns associated with volatility ofthe crosslinking agent.
  • copolymerizable crosslinking agents include copolymerizable anthraquinones, copolymerizable acetophenones, copolymerizable benzophenones, copolymerizable triazines, and mixtures thereof.
  • Copolymerizable crosslinking agents useful in the invention can be found in U.S. Patent Nos.
  • Non-polymerizable radiation activatable crosslinking agents are either mixed with or reacted with the radiation crosslinkable polymer subsequent to polymerization ofthe polymer, or are mixed with the monomer(s) for the polymer prior to polymerization but, in this event, do not react with the monomer(s). Included within this class are multifunctional crosslinking agents and graftable crosslinking agents.
  • One advantage associated with the use of non-polymerizable crosslinking agents is that they are more versatile because they are added to the polymer subsequent to polymerization.
  • the non-polymerizable type need not be miscible, compatible or reactive with the monomers from which the polymer is derived.
  • Preferred non-polymerizable crosslinking agents are anthraquinone, substituted anthraquinone, multi-functional acetophenones, multi-functional benzophenones, substituted triazines, and mixtures thereof.
  • Specific examples of useful anthraquinone- type non-polymerizable crosslinking agents include anthraquinone, t-butyl anthraquinone and 2-ethyl anthraquinone.
  • Particularly preferred as non-polymerizable radiation activatable crosslinking agents are multi-functional acetophenones and benzophenones having the following formula: wherein:
  • X represents CH 3 -; phenyl; or substituted-phenyl; W represents -O-,-NH-, or -S-;
  • Z represents an organic spacer selected from the group consisting of aliphatic, aromatic, aralkyl, heteroaromatic, and cycloaliphatic groups free of esters, amides, ketones, urethanes, and also free of ethers, thiols, allylic groups, and benzylic groups with hydrogen atoms not intramolecularly accessible to the carbonyl group in formula (I); and n represents an integer of 2 or greater; preferably 2-6.
  • X is phenyl
  • W is oxygen
  • Z is -(-CH 2 -)- 2 . ⁇ 2
  • n is 2.
  • preferred multi-functional benzophenones include l,5-bis(4- benzoylphenoxy)pentane, l,9-bis(4-benzoylphenoxy)nonane, and l,l l-bis(4- benzoylphenoxy)undecane.
  • substituted triazine crosslinking agents include 2,4-bistrichloromethyl-6-(4-methoxyphenyl)-s-triazine, and 2,4-bistrichloromethyl-6-(3 ,4- dimethoxyphenyl)-s-triazine.
  • Combinations of copolymerizable and non-polymerizable radiation activatable crosslinking agents can also be used in the radiation crosslinkable compositions described above and this provides a second aspect ofthe invention.
  • copolymerizable crosslinkers are effective in many radiation curable compositions, but are less useful in some situations.
  • the initiation conditions used to form a polymer containing a certain level of polymerizable radiation activatable crosslinking agent can also activate the photoactive group present in the inco ⁇ orated crosslinker.
  • One undesired result of activating the crosslinking agent during polymerization can be premature gelation. Reducing the copolymerizable crosslinking agent level can decrease or eliminate unwanted gelation, and may also reduce the degree of crosslinking when the polymer is subsequently irradiated during the intended crosslinking process.
  • non-polymerizable radiation-activatable crosslinking agents capable of abstracting hydrogen when activated can be combined with a radiation crosslinkable polymer having radiation activatable crosslinking groups capable of abstracting hydrogen when activated.
  • a broad spectrum of crosslinking levels can be obtained by adding a non- polymerizable radiation-activatable crosslinking agent of this type to a radiation crosslinkable polymer that includes radiation-activatable crosslinking groups likewise capable of abstracting hydrogen atoms when activated.
  • Combinations of copolymerizable and non-polymerizable crosslinking agents are also useful in curing radiation crosslinkable polymers that have been diluted with certain oligomeric or polymeric additives.
  • Such additives can diminish the efficiency of inco ⁇ orated crosslinkers by a variety of mechanisms, including inhibition ofthe crosslinking reaction by reducing the concentration ofthe photoactive species in the diluted system and by absorbing the energy required to activate the crosslinker.
  • Additives that have abstractable hydrogens can inhibit or terminate the crosslinking reaction through chain-transfer or chain-termination mechanisms and result in a decreased level of crosslinking.
  • the inco ⁇ orated crosslinking agent can be advantageously supplemented by adding a sufficient amount of a non-polymerizable crosslinking agent to overcome the deleterious effects ofthe polymeric or oligomeric additives.
  • a non-polymerizable crosslinking agent can increase the concentration ofthe crosslinking agent for curing diluted systems, but can also allow the formulator the flexibility of adding crosslinking agents that have a different abso ⁇ tion or photoactivation character than those inco ⁇ orated into the radiation crosslinkable polymer. This latter benefit is particularly useful if the oligomeric or polymeric additive absorbs UV radiation at wavelengths that inhibit photoactivation ofthe inco ⁇ orated crosslinking agent.
  • Poly(meth)acrylates are preferred for use as the abstractable hydrogen- containing radiation-crosslinkable polymer in the second aspect ofthe invention.
  • Poly(meth)acrylates can be prepared by a variety of polymerization methods, including emulsion, suspension, solvent, solution, or bulk polymerization. These polymerization methods are described in Principles of Polymerization, 3rd ed. (G. Odian, Wiley-Interscience : New York, 1981, pp. 286-296).
  • Those poly(meth)acrylates prepared using suspension polymerization are especially preferred for use in the second aspect ofthe invention and can be made according to the methods described in U.S. Patent Nos.
  • the suspension polymers are generally in the form of spherical or pearl-shaped beads typically having a diameter of at least 1 ⁇ m, with diameters of up to 1000 ⁇ m or more being possible.
  • these polymerization methods first involve preparing a monomer premix.
  • the premix typically comprises acrylate and/or methacrylate monomers, optional ethylenically unsaturated free radically polymerizable monomers, chain transfer agent, and free radical initiator. If used, a copolymerizable radiation activatable crosslinking agent is also added to the premix.
  • the premix is then combined with a water phase comprising a suspending agent, water, and, optionally, a surfactant.
  • a modifier moiety such as hydrophobic silica, polystyryl methacrylate macromonomers and/or reactive zinc salt can be added to the suspension mixture before, during or after polymerization.
  • a non-polymerizable radiation activatable crosslinking agent capable of abstracting hydrogens when activated can also be added to the radiation crosslinkable polymer made according to these methods.
  • An example of how a radiation crosslinkable polymer having radiation-activatable crosslinking groups can be effectively combined with non-polymerizable radiation- activatable crosslinking agents is to crosslink poly(meth)acrylate adhesive polymers that have been diluted with tackifying resins.
  • Tackifying resins typically employed in poly(meth)acrylate adhesives are low molecular weight organic compounds derived from natural sources and based on rosin acids, selected phenol-modified te ⁇ enes, and alpha- pinenes. These resins promote adhesion, but often at the expense ofthe adhesive's bulk or cohesive strength.
  • the tackifying resin can provoke several ofthe deleterious effects mentioned above that are associated with oligomeric and polymeric additives (i.e., abso ⁇ tion of energy required to activate the inco ⁇ orated crosslinker, undesired chain transfer or chain termination reactions, etc.).
  • poly(meth)acrylates having radiation-activatable crosslinking groups can be effectively combined with non-polymerizable radiation activatable crosslinking agents to yield the radiation crosslinkable composition. Such a combination may provide enhanced adhesive performance when compared to the sole use of an equivalent amount ofthe non- polymerizable radiation activatable crosslinking agents.
  • the radiation-activatable crosslinking groups are preferably derived from radiation-activatable crosslinking agents having a polymerizable group.
  • Useful polymerizable radiation-activatable crosslinking agents for use in this embodiment include polymerizable acetophenones, polymerizable benzophenones, polymerizable anthraquinones, and mixtures thereof. Further polymerizable crosslinking agents useful in the invention can be found in U. S. Patent Nos.
  • Preferred polymerizable crosslinking agents are the (meth)acrylate-functional aromatic ketones disclosed in U.S. Patent No. 4,737,559 (Kellen et al ), in particular 4-acryloxybenzophenone.
  • the latter type of polymerizable crosslinking agents are particularly preferred in the preparation of a poly(meth)acrylate polymer having radiation-activatable crosslinking groups that are capable of abstracting hydrogen atoms upon activation.
  • Preferred non-polymerizable crosslinking agents for use in the second aspect of the invention are those selected form the group consisting of non-polymerizable anthraquinone including non-polymerizable substituted anthraquinone, non-polymerizable multi-functional acetophenones, non-polymerizable multi-functional benzophenones, and mixtures thereof.
  • useful anthraquinone-type non-polymerizable crosslinking agents include anthraquinone, t-butyl anthraquinone and 2-ethyl anthraquinone.
  • Examples of useful non-polymerizable multifunctional acetophenones and benzophenones are those of Formula (I) set forth above.
  • the radiation-activatable crosslinking agents whether they have been copolymerized into the radiation-crosslinkable polymer or they are ofthe non- polymerizable type (for either aspect ofthe invention), are typically employed, either singly or in combination, in an effective amount by which is meant an amount large enough to provide the desired ultimate properties.
  • an effective amount of crosslinking agent is an amount sufficient to crosslink the polymer so that it has adequate cohesive strength but not in an amount so large that the polymer becomes overcured.
  • the actual amount of crosslinking agent used will vary depending on the application, the type of polymer, the type of crosslinking agent, the ease of hydrogen abstraction from the polymer, the reactivity of the radicals formed, the intensity and length of exposure ofthe composition to irradiation, the polymer's molecular weight, and the desired final properties ofthe material.
  • the total amount of crosslinking agent is preferably about 0.01 to 25 weight %, more preferably about 0.1 to 10 weight %, and most preferably about 0.1 to 1.0 weight %, based upon the total weight ofthe polymer.
  • crosslinked polymers may be readily produced according to the invention.
  • the crosslinking agent is blended or combined with the other monomers that will yield the polymer, the crosslinking agent being miscible, compatible, and reactive with these monomers.
  • the monomers are then polymerized in any conventional manner such as anionic, cationic and free-radical techniques well known to those skilled in the art.
  • the crosslinking agent is mixed with the preformed polymer by dissolving in a solvent, extruding with the polymer, or other standard compounding techniques for combining a non-polymerizable crosslinking agent with a polymer.
  • the non-polymerizable crosslinking agent may be combined with the monomer(s) prior to polymer formation but, in this event, does not react with the monomer(s).
  • the crosslinking agent/polymer composition can be irradiated directly or applied to a substrate by methods well-known in the art, such as solvent coating, extrusion coating, (e.g., hot melt extrusion coating), solventless or waterbome coating.
  • solvent coating e.g., hot melt extrusion coating
  • solventless or waterbome coating e.g., solventless or waterbome coating.
  • the compositions can be applied to at least a portion of at least one major surface of a suitable flexible or rigid substrate or surface.
  • Useful flexible substrates or webs include paper, plastic films such as polypropylene), poly(ethylene), poly(vinyl chloride), polytetrafluoroethylene), polyester [e.g., poly(ethylene terephthalate)], polyimide film such as DuPont' s KaptonTM, cellulose acetate, and ethyl cellulose.
  • Substrates can also be woven fabric formed of threads of synthetic or natural materials such as cotton, nylon, rayon, glass, or ceramic material, or they can be of nonwoven fabric such as air-laid webs of natural or synthetic fibers or blends of these.
  • suitable substrates can be formed of metal, metallized polymeric film, or ceramic sheet material.
  • Suitable rigid substrates include glass, wood, metal, treated metal (such as those comprising automobile and marine surfaces), polymeric, and composite materials such as fiber-reinforced plastics.
  • excimer lasers and excimer lamps may provide monochromatic radiation source, the latter arc preferred for several reasons including more efficient irradiation of a larger physical area.
  • An excimer lamp may comprise a single lamp or a bank of lamps, preferably arranged to irradiate an area somewhat larger than the target substrate so as to ensure uniform radiation exposure over the entire area.
  • an excimer laser it may be helpful to provide a lens system to distribute the radiation over a wider physical area.
  • the radiation crosslinkable compositions that have been described herein are useful in various applications including as adhesives (especially, pressure sensitive adhesives and pressure sensitive adhesive-coated articles such as tapes, sheets, labels, etc.), coatings, sealants, photoresists and hardcoats.
  • TEST PROCEDURES The following test procedures were used to evaluate the compositions prepared in the examples. The compositions were useful as adhesives.
  • Shear strength is a measure ofthe cohesiveness or internal strength of an adhesive. It is based upon the amount of force required to pull an adhesive strip (tape) from a standard flat surface in a direction parallel to the surface to which it has been affixed with a definite pressure. It is measured as the time in minutes required to pull a standard area of adhesive-coated sheet material from a stainless steel test panel under stress of a constant, standard load. This test follows the procedure described in ASTM D 3645M-88: "Holding Power of Pressure Sensitive Adhesive Tapes.”
  • High temperature shear strength was measured as described in the shear strength test except that the test samples were first aged at 70° C for 15 minutes, and then tested at 70° C. The reported results are an average of two samples.
  • Results are an average of two numbers and are reported to the nearest whole number.
  • the mixture was cooled by the addition of 2500 g water and the precipitated product was filtered from the ethylene glycol/water mixture.
  • the tan, solid precipitate was then mixed with 3608 g ethyl acetate to purify the product.
  • the ethyl acetate purification step was repeated and, following air drying, 2982 g of purified C5EBP was obtained.
  • a series of acrylate pressure sensitive adhesives was prepared according to the method of U.S. Patent Re. 24,906 (Ulrich), inco ⁇ orated by reference herein, in ethyl acetate using 90 wt.% isooctyl acrylate, 10 wt.% acrylic acid, and 0.1 wt.% carbon tetrabromide (CBr 4 ) chain transfer agent.
  • the inherent viscosity of each of the resultant adhesives was 0.64 dl/g in ethyl acetate at 27° C.
  • a non-polymerizable radiation-activatable crosslinking agent ofthe type and amount (amt.) specified in Table 1 below was dissolved in a 40 wt.% solution of each adhesive in ethyl acetate.
  • the amount of crosslinking agent reported for examples 3 to 5 represents the weight % based on the weight ofthe polymer.
  • the amounts reported for examples 6 to 8 are a calculated weight %, based on having actually used an equivalent molar percentage when compared to examples 3 to 5.
  • These mixtures were then knife coated onto a 38 ⁇ m thick aziridine-primed poly(ethylene terephthalate) film and dried for 15 minutes at 65° C. to yield 25 ⁇ m thick coatings.
  • the coated films were passed through a curing chamber at a speed of approximately 1.6 meters per minute under the output of a 308 nm XeCl excimer lamp (Model Excimer Lamp 308, commercially available from Heraeus Noblelight, Hanau, Germany) in which the lamp was mounted on a conveyor belt system at a height of approximately 2.5 cm above the belt.
  • Table 1 shows the total energy dose received by each example. (All excimer energy doses herein were measured in the UVB (280- 320 nm) range.)
  • the cured samples were stored for 24 hours in a constant temperature room held at 22° C. and 50% relative humidity.
  • the gel fraction for each example was measured as described above using ethyl acetate as the solvent. Room temperature shear strengths were also measured as described above. The gel fraction and shear strength data for each of these examples can be found in Table 1.
  • the following examples demonstrate the use of a XeCl excimer laser to crosslink the acrylate pressure-sensitive adhesives of Examples 3-8 using different amounts of C5EBP non-polymerizable crosslinking agent and different adhesive thicknesses as shown below in Table 2.
  • the mixtures were knife coated onto a 38 ⁇ m thick, flexible, aziridine-primed poly(ethylene terephthalate) web, dried at 65° C for 15 minutes, and cured using a Lambda Physik (G ⁇ ttingen, Germany) 300i Series XeCl excimer laser having a maximum intensity at 308 nm and a maximum pulse frequency of 150 Hz.
  • the beam was optically spread using quartz optics to cover an area 0.03 dm high and 1.52 dm wide with an average energy per pulse of about 100 mJ/cm .
  • Samples to be irradiated were attached to the platform of an xy-translation stage positioned in the vertical orientation, allowing the sample to be passed normal to the incident excitation pulses at variable speeds. Dose was controlled primarily by changing the speed ofthe substrate. Table 2 shows the total energy dose received by each example.
  • the gel fraction for each example was measured as described above using ethyl acetate as the solvent and with the results reported below in Table 2.
  • compositions that inco ⁇ orate varying amounts of a non-polymerizable crosslinking agent can be crosslinked using an excimer laser as the monochromatic radiation source.
  • EXAMPLES 12-15 An emulsion polymerized acrylic pressure-sensitive adhesive comprising 94.5 parts isooctyl acrylate and 5.5 parts acrylic acid having an inherent viscosity of 2.05 dl/g in ethylacetate at 27° C was prepared according to U.S. Pat. No. Re. 24,906 (Ulrich). The adhesive was dried and then dissolved in a 70/30 toluene/isopropanol solvent mixture (25 wt% solids), along with the amounts and types of non- polymerizable crosslinking agents found in Table 3.
  • Examples 16-19 illustrate the advantages gained when a copolymerizable crosslinking agent (ABP) is used alone and when it is combined with a non- polymerizable crosslinking agent (C5EBP) in a radiation crosslinkable polyacrylate pressure-sensitive adhesive.
  • a partially polymerized pre-adhesive composition was prepared by mixing 90 parts isooctyl acrylate, 10 parts acrylic acid, 0.15 % Irgacure 651 (photoinitiator commercially available from Ciba-Geigy), and 0.025 % CBr 4 chain transfer agent (the percentages for the latter two components being based on the combined amount of isooctyl acrylate and acrylic acid).
  • the mixtures were irradiated with low intensity ultraviolet light until a partially polymerized pre-adhesive composition having a coatable viscosity was obtained.
  • a partially polymerized pre-adhesive composition having a coatable viscosity was obtained.
  • the compositions were knife-coated at a thickness of 2.5 mm between two sheets of 0.005 mm thick UV-transparent polyester films coated with a silicone release layer.
  • Zone 1 was at approximately 187 mJ/cm 2 of energy at a light intensity of 0.4 milliwatts/cm 2 .
  • Zone 2 was at an energy of approximately 563 mJ/cm 2 at a light intensity of 2.0 milliwatts/cm 2 .
  • the coated sandwich construction was cooled by air impingement to remove the heat of polymerization.
  • the polyester sheets were removed from the sandwich construction, the polymerized composition was placed in a hot melt coater/extruder, and the melted composition was coated onto a silicone-treated release liner at a thickness of either 51 ⁇ m (Examples 16 and 17) or 127 ⁇ m (Examples 18 and 19), and then transfer laminated onto a 38 ⁇ m thick, flexible, aziridine-primed poly(ethylene terephthalate) film.
  • the coated samples were then cured using the system described in Examples 3- 8 to provide the total energy dose shown in Table 5.
  • the gel fraction (in ethyl acetate) and shear strength both room temperature and high temperature) were measured for the examples as described above and with the results shown in Table 4.
  • copolymerizable crosslinking agents can be used in the practice ofthe invention. Furthermore, the addition of a non-polymerizable crosslinking agent to an elastomeric adhesive composition that included a copolymerizable crosslinking agent enhanced the degree of crosslinking as reflected by comparing examples 19 and 21 with, respectively, examples 18 and 20. These examples also demonstrate that the combination of an excimer light source and a radiation activatable crosslinking agent can be effectively used to cure a relatively thick film of elastomeric material without overcuring the surface ofthe material.
  • the emulsion polymerized acrylic pressure-sensitive adhesives of examples 20-22 were prepared and tested following the procedures described in conjunction with examples 12-15 except that the adhesives were coated to a dry thickness of 25 ⁇ m.
  • the amount of crosslinking agent reported for example 20 represents the weight % based on the weight ofthe polymer.
  • the amounts reported for examples 21 and 22 are a calculated weight % based on having actually used an equivalent molar percentage when compared to example 20.
  • Table 5 shows the total energy dose received by each example, the gel fraction, and the room temperature shear strength values. TABLE 5
  • Room temperature shear strength values are reported as either an average of two samples if both failed prior to 10,000 minutes or as two individual samples if only one failed prior to 10,000 minutes. All samples having less than 10,000 minutes shear strength demonstrated at least some cohesive failure. These examples show that the methods ofthe invention are an effective means of crosslinking a radiation crosslinkable polymer. Since these examples either survived for more than 10,000 minutes in the room temperature shear strength test or demonstrated at least some cohesive failure, the polymer surface was not overcured.
  • Examples 23-40 illustrate the use of excimer lamps for crosslinking various elastomers (polybutadiene, polyisoprene, and triblock copolymer) combined with a range of radiation activatable crosslinking agents.
  • Polybutadiene having a weight average molecular weight of 119,000 and polyisoprene having a weight average molecular weight of 263,000 were prepared by standard anionic polymerization techniques in cyclohexane using sec-butyl lithium as the initiator.
  • KratonTM 1107 is a styrene-isoprene-styrene triblock copolymer commercially available from Shell Co.
  • Example 42 shows the use of a monochromatic radiation source to crosslink a thermoplastic composition, poly(vinyl acetate).
  • Poly(vinyl acetate) having an average molecular weight of 500,000 was obtained from Aldrich Chemical Company and dissolved in chloroform to provide a 25% solids solution.
  • the solution was then knife coated onto a 38 ⁇ m thick, aziridine-primed poly(ethylene terephthalate) film and dried for 15 minutes at 65° C to yield a 25 ⁇ m thick coating, but did not adhere well to the film.
  • the coated sample was then cured in a static condition for 15 seconds under the output ofthe 308 nm XeCl excimer lamp referred to in Examples 3-8. Total dose received was 889 mJ/cm 2 .
  • Gel fraction was determined following the test procedure described above using chloroform as the solvent. The gel fractions were 0% and 16% for the control (i.e., no radiation exposure) and example 42, respectively. This example demonstrates the utility ofthe processes ofthe invention in crosslinking a thermoplastic polymer.
  • Comparative examples C-3 and C-4 show the use of a conventional mercury lamp ultraviolet light source to process compositions similar to those of Examples 20-22.
  • Emulsion polymerized acrylic pressure sensitive adhesives were prepared according to the procedure described in conjunction with Examples 20-22, using the types and amounts of non-polymerizable crosslinking agent shown in Table 8.
  • the coated samples were then cured by the use of a Fusion Systems UV processor using an "H" bulb at full power and a conveyor speed of 22.9 meters/min. (75 feet/min ).
  • these comparative examples having similar gel fractions demonstrated a significant decrease in shear strength and a change in the shear failure mode.
  • the diminished shear strength can be attributed to the undesired emissions inherent in the conventional, broad spectral output mercury bulbs used to prepare these examples.
  • a 25 wt. % solventborne natural rubber-based adhesive composition was prepared by combining 50 parts natural rubber (a CV-60 Standard Malaysian Rubber (SMR) natural rubber), 50 parts by weight styrene-butadiene rubber (SBR 1011 A, commercially available from Ameripol/Synpol), 50 parts by weight aliphatic hydrocarbon tackifying resin (Escorez 1304, commercially available from Exxon Chemical Co.), 1 part by weight Irganox 1010 (a multi-functional hindered phenol antioxidant, commercially available from Ciba-Geigy Co ⁇ .), and 0.1 part C9EBP crosslinking agent in toluene.
  • SMR CV-60 Standard Malaysian Rubber
  • SBR 1011 A commercially available from Ameripol/Synpol
  • Escorez 1304 commercially available from Exxon Chemical Co.
  • Irganox 1010 a multi-functional hindered phenol antioxidant, commercially available from Ciba-Geigy Co ⁇ .
  • C9EBP crosslinking agent was prepared like C5EBP described in example 1 except that the 1,5-dibromopentane was replaced with an equimolar amount of 1,9- dibromononane.
  • the adhesive composition was coated on a primed polyester film and dried to a thickness of 25 ⁇ m.
  • the coated sample was then crosslinked using the XeCl excimer lamp system described in Examples 3-8 while in example C-5, the coated film was cured by a PPG high intensity UV processor (PPG Inc., Pittsburgh, PA) with two lamps at the normal setting and a conveyor speed of 18.3 meters/min. (60 feet per minute).
  • Table 9 shows the total energy dose received by each sample and the gel fraction (in toluene) and room temperature shear strength values ofthe adhesives as measured by the methods described above.
  • a 2 liter split reaction flask equipped with a condenser, thermometer, nitrogen inlet, motor driven agitator, and a heating mantle with temperature control was first charged with the ingredients ofthe dispersion medium described below in Table 10 and then heated to 58 °C.
  • the dispersion medium was maintained at this temperature with agitation and nitrogen purging for one hour to remove oxygen.
  • a premixed charge ofthe oil phase described below in Table 10 was added to the reactor under vigorous agitation (700 ⁇ m) to obtain a good suspension.
  • the reaction was continued with nitrogen purging throughout the polymerization. After the exotherm ofthe reaction was reached, the reaction was continued at 75 °C for another 2 hours, and then the batch was cooled to room temperature.
  • reaction mixture was then dried to remove the suspension medium and the dried suspension polyacrylate was dissolved in ethyl acetate at 30% concentration. 230 parts ofthe polyacrylate solution was then blended with 30 parts ForalTM 85 (rosin ester tackifying resin commercially available from Hercules Inc.) and, for examples 43-49, additionally combined with the amounts C5EBP non- polymerizable crosslinking agent specified in Table 11.
  • ForalTM 85 Rosin ester tackifying resin commercially available from Hercules Inc.
  • the tackified polyacrylate blends were coated onto 38 ⁇ m thick aziridine-primed poly(ethylene terephthalate) film to a dried thickness of 25 ⁇ m and cured by the use of a PPG high intensity UV processor (PPG Inc., Pittsburgh, PA) with two lamps at the normal setting and a conveyor speed of 18.3 meters/min. (60 feet per minute).
  • the total energy dose received by each example was 275 mJ/cm 2 .
  • the room temperature and high temperature shear strength of each cured sample was measured as described above, except that the high temperature measurements were made using a 500 gram hanging weight.
  • Example pairs C-6 and 44, C-7 and 45, C-8 and 46, C-9 and 47, C-10 and 48, C-11 and 49, and C-12 and 50 demonstrate a marked increase in shear strength found when a combination of polymerizable and non-polymerizable crosslinking agents is used to cure tackified suspension polymerized polyacrylate pressure sensitive adhesive formulations.
  • the formulation containing only non- polymerizable crosslinking agent provided lower shear strengths than the corresponding example having an equivalent amount (on a molar basis) of combined crosslinking agents.
  • Examples 51 to 59 were prepared by adding to the corresponding comparative example C5EBP non-copolymerizable radiation-activatable crosslinking agent in the amount specified in Table 12 below by dissolving in a 40 wt.% solution of each adhesive in ethyl acetate. All of these examples were then blended with 30 parts of ForalTM 85 (rosin ester tackifying resin commercially available Hercules Inc.) per one hundred parts adhesive solution, knife coated onto a 38 ⁇ m thick aziridine- primed poly(ethylene terephthalate) film, and dried for 15 minutes at 65°C to yield 25 ⁇ m thick coatings.
  • ForalTM 85 Rosin ester tackifying resin commercially available Hercules Inc.
  • the coated samples were then cured by the use of a Fusion Systems UV processor using an "FT bulb at full power and a conveyor speed of 30.5 meters/min. (100 feet/min.). Each sample was exposed to three different levels of UV radiation and the total energy dose received by each sample is recorded in Table 12 (measured in the UVA (320-390 nm) range), along with the room temperature shear strength as measured by the method described above.

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  • Polymers & Plastics (AREA)
  • General Chemical & Material Sciences (AREA)
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  • Processes Of Treating Macromolecular Substances (AREA)
  • Polymerisation Methods In General (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
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Abstract

Cette invention a trait, d'une manière générale, à un procédé permettant d'effectuer une réticulation de polymère par rayonnement. Il est possible d'utiliser une source de rayonnement monochrome ( une lampe ou un laser excimère, par exemple) pour réticuler des élastomères et des polymères thermoplastiques entrés en composition avec un agent de réticulation activé par un rayonnement, comme de l'anthraquinone, de l'anthraquinone substituée, des acétophénones (du type polyvalent ou copolymérisable), des benzophénones (du type polyvalent ou copolymérisable) ou de la triazine substituée. L'invention a également trait à une composition susceptible d'être réticulée sous l'effet d'un rayonnement et, notamment, à des compositions associant des agents de réticulation, polymérisables et non polymérisables, activés par un rayonnement.
PCT/US1997/006166 1996-04-19 1997-04-16 Procede de reticulation de polymeres par rayonnement et compositions susceptibles d'etre reticulees sous l'effet d'un rayonnement WO1997040090A2 (fr)

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BR9708703A BR9708703A (pt) 1996-04-19 1997-04-16 Processo para reticular um polímero e um elastômero e fabricar uma fita adesiva flexível sensível a presão composição reticulavel por radiação adesivo sensível a pressão e artigo revestido com adesivo sensível a pressão
EP97920385A EP0894112A2 (fr) 1996-04-19 1997-04-16 Procede de reticulation de polymeres par rayonnement et compositions susceptibles d'etre reticulees sous l'effet d'un rayonnement
JP9538142A JP2000509089A (ja) 1996-04-19 1997-04-16 ポリマを放射線架橋する方法及び放射線架橋性組成物

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EP1086959A1 (fr) * 1999-03-30 2001-03-28 Idemitsu Petrochemical Co., Ltd. Copolymere reticule d'acide carboxylique insature et son procede de production, copolymere d'acide carboxylique insature, adjuvant biodegradable, et composition detergente
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US6242504B1 (en) * 1997-09-29 2001-06-05 Basf Aktiengesellschaft Crosslinking of radiation-crosslinkable pressure-sensitive adhesive films
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EP2733186A1 (fr) 2012-11-19 2014-05-21 3M Innovative Properties Company Adhésifs sensibles à la pression à base d'acrylate rendue hautement adhérente
FR3045641A1 (fr) * 2015-12-22 2017-06-23 Bluestar Silicones France Utilisation d'un systeme photoamorceur de type ii pour la reticulation de compositions silicones
WO2018005585A1 (fr) 2016-06-29 2018-01-04 3M Innovative Properties Company Adhésifs sensibles à la pression, à base de (co)polymères de (méth)acrylate, poisseux, réticulables par un rayonnement ionisant, à faible teneur en acide
US10829675B2 (en) 2012-09-25 2020-11-10 Cold Chain Technologies, Llc Gel comprising a phase-change material, method of preparing the gel, thermal exchange implement comprising the gel, and method of preparing the thermal exchange implement
US10961379B2 (en) 2015-03-06 2021-03-30 3M Innovative Properties Company Ultraviolet crosslinkable composition comprising an acrylic polymer having an ultraviolet crosslinkable site

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JP4817675B2 (ja) 2005-03-02 2011-11-16 スリーエム イノベイティブ プロパティズ カンパニー （メタ）アクリル系フィルム、及びそれを用いたマーキングフィルム、レセプターシート
KR20140030206A (ko) * 2011-04-26 2014-03-11 쓰리엠 이노베이티브 프로퍼티즈 컴파니 혼합 광가교결합 시스템을 갖는 감압 접착제
KR102474200B1 (ko) * 2017-12-27 2022-12-02 일디즈 테크닉 유니버시티 광개시제 및 라텍스의 광-가황
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US6242504B1 (en) * 1997-09-29 2001-06-05 Basf Aktiengesellschaft Crosslinking of radiation-crosslinkable pressure-sensitive adhesive films
EP0964003A2 (fr) * 1998-06-11 1999-12-15 3M Innovative Properties Company Procédé de polymérisation par radicaux libres utilisant un rayonnement monochromatique
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US6517910B2 (en) 1998-06-11 2003-02-11 3M Innovative Properties Company Free radical polymerization method
EP1086959A1 (fr) * 1999-03-30 2001-03-28 Idemitsu Petrochemical Co., Ltd. Copolymere reticule d'acide carboxylique insature et son procede de production, copolymere d'acide carboxylique insature, adjuvant biodegradable, et composition detergente
EP1086959A4 (fr) * 1999-03-30 2005-02-02 Copolymere reticule d'acide carboxylique insature et son procede de production, copolymere d'acide carboxylique insature, adjuvant biodegradable, et composition detergente
US7691948B2 (en) 2003-09-09 2010-04-06 3M Innovative Properties Company (Meth)acrylic film, and making film and receptor sheet using the same
US10829675B2 (en) 2012-09-25 2020-11-10 Cold Chain Technologies, Llc Gel comprising a phase-change material, method of preparing the gel, thermal exchange implement comprising the gel, and method of preparing the thermal exchange implement
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US10035931B2 (en) 2012-11-19 2018-07-31 3M Innovative Properties Company Highly tackified acrylate pressure sensitive adhesives
WO2014078118A1 (fr) 2012-11-19 2014-05-22 3M Innovative Properties Company Adhésifs à base d'acrylate très poisseux et autocollants
US9701873B2 (en) 2012-11-19 2017-07-11 3M Innovative Properties Company Highly tackified acrylate pressure sensitive adhesives
EP2733186A1 (fr) 2012-11-19 2014-05-21 3M Innovative Properties Company Adhésifs sensibles à la pression à base d'acrylate rendue hautement adhérente
US10961379B2 (en) 2015-03-06 2021-03-30 3M Innovative Properties Company Ultraviolet crosslinkable composition comprising an acrylic polymer having an ultraviolet crosslinkable site
CN109072001A (zh) * 2015-12-22 2018-12-21 埃肯有机硅法国简易股份公司 Ii型光引发剂体系用于交联硅酮组合物的用途
US10954384B2 (en) 2015-12-22 2021-03-23 Elkem Silicones France Sas Type II photoinitiator system and method for crosslinking silicone compositions
WO2017109116A1 (fr) * 2015-12-22 2017-06-29 Bluestar Silicones France Sas Utilisation d'un système photoamorceur de type ii pour la réticulation de compositions silicones
CN109072001B (zh) * 2015-12-22 2021-09-28 埃肯有机硅法国简易股份公司 Ii型光引发剂体系用于交联硅酮组合物的用途
US11603468B2 (en) 2015-12-22 2023-03-14 Elkem Silicones France Sas Type II photoinitiator system and method for forming crosslinking silicone compositions
FR3045641A1 (fr) * 2015-12-22 2017-06-23 Bluestar Silicones France Utilisation d'un systeme photoamorceur de type ii pour la reticulation de compositions silicones
WO2018005585A1 (fr) 2016-06-29 2018-01-04 3M Innovative Properties Company Adhésifs sensibles à la pression, à base de (co)polymères de (méth)acrylate, poisseux, réticulables par un rayonnement ionisant, à faible teneur en acide

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WO1997040090A3 (fr) 1997-11-27
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BR9708703A (pt) 1999-08-03
KR20000005547A (ko) 2000-01-25

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