MXPA00011928A - Free radical polymerization method - Google Patents

Abstract

In one aspect the invention provides an energy efficient polymerisation method comprising irradiating a polymerizable composition and a photoinitiator with a source of essentially monochromatic radiation where the photoinitiator and the wavelength of the radiation source are selected such that the extinction coefficient of the photoinitiator at the peak wavelength of the source is greater than about 1000 M-1 cm-1 and such that the photoinitiator absorbs at least two percent of the actinic radiation incident on the coating. In another aspect the invention provides energy efficient methods of polymerizing polymerizable compositions and cross-linking cross-linkable compositions by irradiating the respective compositions with a low power source of essentially monochromatic radiation. The low power energy sources have an input power of less than about 10 W/cm. Articles made from the above methods, including polymer films having release coatings, adhesive coatings, hard coatings and the like thereon, also are provided.

Description

METHOD OF POLYMERIZATION OF FREE RADICALS Field of invention The present invention relates, in general, to a process for the polymerization of a radiation-polymerizable composition and, more particularly, to a polymerization process using a monochromatic radiation source. Additionally, an efficient method is described for lattically bonding a polymeric bond that can be crosslinked by radiation.

Background of invention The radiation-induced free radical polymerization of ethylenically unsaturated monomers is known, both with batch and continuous polymerizations, achieved using this technique. While the desire to build a product with a high molecular weight tends to make batch polymerization methods relatively slow, it is generally desirable to achieve a final product in a much shorter time than in cases where Are applied Ref. 125215 polymerization coatings on a substrate. At present, free radical polymerization induced by radiation is carried out by exposing a polymerizable coating at the outlet of a high intensity radiation source, usually a medium pressure mercury lamp or a doped mercury lamp. The photoinitiator (s) present in the coatings absorb certain regions of the spectral production of the lamp that generates free radicals and initiates the polymerization process. However, there is a need to perform radiation-induced free radical polymerization of coatings with greater energy efficiency and shorter residence times, in particular, on substrates that are adversely affected by the heat generated by the sources of radiation. Similar considerations are associated with the lattice bonding of polymer coatings containing crosslinking agents that can be activated by radiation.

Radiation-induced free radical polymerization of coatings comprising ethylenically unsaturated monomers or oligomers is carried out by exposing a coating to the spectral output of a high intensity radiation source comprising one or more bulbs that commonly have a power input per bulb of around 40 W / cm or more. Commonly, these same sources are used for the lattice bond of: polymeric coatings containing binding-crosslinking agents that can be activated by radiation. When a source contains mercury at these power levels, its spectral output is above a wide range of wavelengths, including the ultraviolet, visible and infrared regions of the electromagnetic spectrum. In general, the presence of a species that can be activated by radiation (photoinitiators for a polymerizable coating or a crosslinking photoinner for a polymer coating) is necessary for these systems to work. In general, photoinitiators and reticular photo linkers are not absorbed appreciably, either in the visible or infrared regions of the spectrum and, therefore, only a small percentage of the total production of the spectrum of these is used. sources for inducing the polymerization of a polymerizable coating or for crosslinking a polymer coating. Additionally, the differential absorption by the species that can be activated by radiation within a coating, causes large curing gradients to form between its upper and lower surfaces. Frequently, infrared radiation and radiant heat are also undesirable by themselves, since their presence causes low molecular weight species to volatilize in the coatings, distortions heat-sensitive stocks and in addition shutters and / or shutters are required. safety locks to minimize the ignition potential.

Recently, procedures that use energy in a more efficient way have been introduced. Stark and Wright describe, in WO 97/39837, the use of a monochromatic light source, preferably a xenon chloride excitation lamp with a peak wavelength of 308 nm, to lattice an adhesive composition that can be Coated by a hot melt. In these compositions, the absorption capacity of the photoactivatable network bonding agents at the wavelength of the exciter source is low, thus allowing the penetration of light through the entire coating thickness, causing the formation of a minimum curing gradient.

In WO 97/40090, Wright describes the use of a monochromatic light source, preferably a krypton chloride exciter lamp, with a peak wavelength of 222 nm, to cure radically free polymerizable coatings without the need for a photoinitiator. When photoinitiators are present, light is not used efficiently due to the competent aggression of monomers and polymerizable oligomers.

In WO 96/00740, Nohr and McDonald describe a general method for generating a reactive species by providing a polymolecular photoreactor, comprising a specific sensitizer for a wavelength together with a reactive species that generates the photoinitiator and which irradiates the sensitizer with actinic radiation. In one embodiment, an excitation lamp is used as the radiation source.

There remains a need to carry out the radiation-induced polymerization of radically free polymerizable coatings containing a photoinitiator and, the need to perform radiation-induced reticular bonding of polymeric coatings containing a photoactivatable crosslinking agent with greater energy efficiency. and with a shorter exposure time.

BRIEF DESCRIPTION OF THE INVENTION Briefly, in one aspect, the present invention provided a polymerization method comprising the steps of: a) providing a substrate coated in at least one of its parts with a radiation-polymerizable composition comprising: (i) a monomer, an oligomer, or a mixture thereof, polymerizable, radically free, ethylenically unsaturated; and (ii) a free radical photoinitiator; b) providing a source essentially monochromatic radiation with an effective wavelength to activate said photoinitiator; Y c) exposing the radiation-polymerizable composition to the radiation emitted by the radiation source for a sufficient time to polymerize the composition; wherein, the photoinitiator at the wavelength of the radiation source is selected such that the extinction coefficient of the photoinitiator at the peak wavelength of the source is greater than 1000 M "1 cm" 1 approximately, and in which, the photoinitiator absorbs at least 2% of the actinic radiation emitted by the source incident on the coating.

In another aspect, this invention provides a polymerization method comprising the steps of: a) providing a mobile substrate coated in at least one of its parts with a radiation-polymerizable composition, comprising: (i) a monomer, an oligomer, a mixture of these, polymerizable, radically free, ethylenically unsaturated; and (ii) a free radical photoinitiator; b) providing an essentially monochromatic radiation source comprising one or more lamps, wherein each lamp has an input power of less than about 10 W / cm and an effective wavelength to activate said photoinitiator; and c) exposing the radiation-polymerizable composition to the radiation emitted by the radiation source for a sufficient time for polymerizable composition.

In a further aspect, this invention provided a method, to lattice a polymeric coating, comprising the steps of: a) providing a mobile substrate coated in at least one of its parts with a networkable linkable composition comprising: (i) a polymer crosslinkable by radiation containing extractable hydrogen atoms and, (ii) a radiation binding agent activatable by radiation; b) providing an essentially monochromatic radiation source comprising one or more lamps, wherein each lamp has an input power of less than about 10 W / cm, and a wavelength sufficient to activate the lattice bonding agent to bond in a manner crosslink the polymer; and c) exposing the radiation-bondable composition to the radiation emitted by the monochromatic source for a sufficient time to lattice the polymer. Also provided are articles made from the methods cited above, including polymeric films with release coatings, adhesive coatings, in rigid coatings and the like. The methods provided by the invention make it possible to prepare polymer coatings through the appropriate selection of the wavelength and / or the power of the monochromatic radiation source and the crosslinking photoinitiator or photocleaner. Such methods allow accurate indexing and curing depth to be performed, such that rapid and efficient curing can be used. Also, radiation-induced reticular polymerization and bonding methods, highly efficient in energy terms, are provided.

Detailed description of the preferred modalities In accordance with one aspect of the present invention, a polymerizable composition containing a monomer, an oligomer, with a mixture of these, polymerizable, ethylenically unsaturated, radically free, and a photoinitiator selected in a suitable manner, is exposed to a monochromatic light source, to produce a coating. In a second aspect, a radiation-crosslinkable composition of a polymer with extractable hydrogen atoms, and a photoactivatable crosslinking agent, suitably selected, is exposed to a monochromatic light source to produce a polymeric coating bonded in a manner reticular The type of polymeric coating produced following a method of the invention depends on the materials contained in the composition. Polymeric coatings produced in this way may include release coatings, pressure sensitive adhesives, rigid coatings, primary coatings for adhesives and the like.

Monochromatic light sources are those that have essentially 80, preferably 90, and more preferably 95% or more of their total actinic radiation output within a narrow spectral range defined to be no more than about 25 nm, preferably 15 nm and, more preferably, 10 nm, deviation from the peak wavelength supplied by the source. Additionally, monochromatic light sources that are preferred do not radiate or radiate little heat. Examples of monochromatic light sources include both pulse sources, and continuous sources, in which the output is coherent, such as in a xenon chloride excitation laser, and incoherent, such as in a xenon chloride excitation lamp. . The specific wavelengths emitted by the different sources of excitation will depend on the chemical nature of the excitatory species. The exciter lamps are advantageous with respect to lasers, because the light output occurs over a relatively large area and do not require that the expansion be effective. A monochromatic light source that is preferred is a xenon chloride excitation lamp, operated at approximately 50 W / cm, and with a centered 308 nm output, with a bandwidth of around 10 nm (Heraeus Noblelight, Hanau, Germany). A 240 W / cm xenon chloride excitation lamp (Fusion UV Curing Systems, Gaithersburg, MD) also provides a peak wavelength of 308 nm, but since the energy it emits is distributed over a much wider spectral range , it is not considered a monochromatic light source for the purposes of the invention. While said source of excitation with greater power is able to: increase the energy efficiency of the processed process, when compared to the sources of broadband mercury and impurified mercury, it has a significant associated heat output. to it and, it is less effective than the monochromatic light sources of the present invention.

Monochromatic radiation sources that provide an output within the wavelength range of approximately 170 and 600 nm are useful in the present invention. However, the inherent absorption of the organic monomers, oligomers, mixtures or polymers present, provide practical limits for the useful wavelength range from a particular source to a particular composition. As a consequence, a wavelength range that is preferred ranges from approximately 240 to 600 nm and, more preferably, from approximately 240 to 400 nm.

Preferred excitation lamps have been described in various patent publications including published patent application WO 94/14853 and the application ', of German patent no. DE 4, 302, 555 Al, as well as several literature references, such as Kitamure et al., Applied Surface Science, 54 (1992) 410-423; and Zhang et al., Journal of Adhesion Science and Technology, 8 (10) (1994), 1179-1210.

Another source of monochromatic radiation that is preferred is a low pressure mercury arc lamp having an emission band centered at 254 nm. These lamps, which are often referred to as germicidal lamps, operate at a much lower power than the power of the exciter lamps, which are described above and, typically, require only about 1 W / cm. Low pressure mercury arc lamps are used exhaustively for air and water purification due to their effectiveness with bacteria, mold, yeast, and viruses.

The particular monochromatic light source employed can be used in either focused or unfocused mode. In cases where more than one lamp is used, the space between the lamps can be adjusted to provide an optimum average irradiation level. Alternatively, a given lamp or a plurality of lamps may have a variable input power, such as a lamp with intensity reduction. You can also use filters to reduce the intensity of a particular monochromatic light source if it is considered convenient to make such a decrease. Similarly, a non-uniform irradiation profile may be employed in the case where several lamps are present. The monochromatic lamps of the invention can be directly mounted on the coating to be cured, separated only by an air or nitrogen gap or, preferably, they can be isolated from the coatings with some transparent or semi-transparent barrier layer, such as a film. transparent polymer or a quartz window. In those cases in which a coating is applied to a transparent or semitransparent substrate with the wavelength of the monochromatic source, the radiation of the coating can take place through the substrate. Examples of transparent or semi-transparent substrate include polyester, biaxially oriented polypropylene and polyethylene. Polyolefin films are particularly useful due to their high UV transmission and, consequently, they are preferred.

The radically free, ethylenically unsaturated polymerized materials may be monomers, oligomers, or mixtures thereof. Useful classes include, for example, functional vinyl monomers that are monofunctional, difunctional or polyfunctional; radically free polymerizable macromers and radically free, ethylenically unsaturated polymerizable polysiloxanes. Generally, in the radically free, ethylenically unsaturated, polymerizable monomers used in this invention are functional vinyl starting materials. Such initial vinyl materials include, but are not limited to, acrylic acid and its esters, methacrylic acid and its esters, vinyl substituted aromatics, vinyl esters, vinyl chloride, acrylonitrile, methacrylonitrile, acrylamide and its derivatives, methacrylamide and its derivatives, and others. polymerizable vinyl monomers by means of free radicals.

Preferably, the radically free, ethylenically unsaturated, polymerizable monomers have the following general structure: [A] B-B (I) wherein A represents a radically free, ethylenically unsaturated reactive functional group; m is a number of some, at least, and B represents a m-radical that is extremely free of aromatics, chlorine and other halides or substituents that significantly absorb the wavelength radiation of the monochromatic light source chosen The absorption of the radiation from such halves or substituents can interfere with the activation of the photoinitiator and, thus prevent the formation of the free radicals necessary to initiate and propagate the desired polymerization. These monomers may be mono, di or polyfunctional (ie, with one, two, three or more radically free reactive functional groups A, respectively) and have one or more functional groups which, preferably, are selected from acrylate functionalities, methacrylate and vinyl ester.

The monofunctional acrylate and methacrylate monomers useful in the method of the invention include compositions of the formula I, wherein A represents H2C = CR1COO- (in which R1 is a hydrogen atom or a metido group), m = l , and B represents a monovalent straight-chain alkyl, a branched alkyl or a cycloalkyl group with from about 1 to about 24 carbon atoms. Examples of such monofunctional acrylate and methacrylate monomers include, but are not limited to, methylacrylate, methyl methacrylate, isooctyl acrylate, 4-methyl-2-pentyl acrylate, 2-methylbutyl acrylate, isoamyl acrylate, sec-butyl acrylate, n-butyl acrylate. , tert-butyl acrylate, isobornylacrylate, butyl methacrylate, ethyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate and mixtures thereof. Preferred acrylate monomers include all those selected from the group consisting of isooctyl acrylate, isononyl acrylate, isoamyl acrylate, isodecyl acrylate, n-butyl acrylate, sec-butyl acrylate and mixtures thereof.

Vinylester monomers suitable for use in the process of the invention include compositions of the formula I, wherein A represents H2C = CHOC (O) -, m = 1, and B represents a monovalent straight or branched chain alkyl group with between 1 and 24 carbon atoms approximately. Such vinyl ester monomers include, but are not limited to, vinyl acetate, vinyl pelargonate, vinyl hexanoate, vinyl propionate, vinyl decanoate, vinyl octanoate, and other monofunctional unsaturated vinyl esters of linear or branched carboxylic acids comprising from 1 to 16 carbon atoms. Preferred vinyl ester monomers include vinyl acetate, vinyl laurate, vinyl caprate, vinyl-2-ethylhexanoate and mixtures thereof.

Monofunctional monomers easily copolymerizable with acrylate, methacrylate and vinylester monomers, are extremely free of aromatics, chlorine and other portions or substituents that significantly absorb the wavelength radiation of the chosen monochromatic light source, can also be used in the compositions of the invention. Such monomers include, but are not limited to, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, sulfoethyl methacrylate, N-vinyl pyrrolidone, N-vinyl caprolactam, acrylamide, t-butyl acrylamide, dimethylamino ethyl acrylamide. , N-octyl acrylamide, acrylonitrile, their mixtures and other similar. Preferred monomers include acrylic acid, N-vinyl pyrrolidone and mixtures thereof.

The radically free copolymerizable macromonomers of formula I, wherein A is H2C = CR1COO- (where R1 represents a hydrogen atom or a methyl group), m is 1, and B is a monovalent polymeric or oligomeric radical with a degree of polymerization greater than or equal to 2 that is extremely free of aromatics, chlorine- and other portions or substituents that significantly absorb radiation of the wavelength of the chosen monochromatic light source, can also be employed in the invention. Examples of such macromonomers include poly (methyl methacrylate) terminated with acrylate, poly (methyl methacrylate) terminated with methacrylate, poly (ethylene oxide) terminated with acrylate, poly (ethylene oxide) terminated with methacrylate, poly (ethylene glycol) acrylate, poly (ethylene glycol) terminated in methacrylate, methoxy poly (ethylene glycol) methacrylate, butoxy poly (ethylene glycol) methacrylate and mixtures thereof. These functionalized materials are those that are preferred because they are readily prepared using well-known ion polymerization techniques and are also highly effective in providing oligomeric and polymeric segments grafted along the major structures of the radically free polymerized acrylate polymer.

The radically free polymerizable monomers of difunctional and polyfunctional acrylate and methacrylate include ester derivatives of alkyl diols, triols, tetroles, etc. (For example, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and pentaerythritol triacrylate). The difunctional and polyfunctional methacrylate acrylate monomers which are described in US Pat. UU No. 4,379,201 (Heilmann et al.), Such as 1,2-ethanediol diacrylate, 1, 12-dodecanediol diacrylate and pentaerythritol tetracrylate can also be used in the present invention. The difunctional and polyfunctional acrylates and methacrylates which include acrylated epoxy oligomers, acrylated aliphatic urethane oligomers, acrylated polyether oligomers and acrylated polyester oligomers, such as those commercially available from UCB Radcure INC., Symrna, GA, under the trade name of Ebecryl and those marketed by Sartomer, Exton, PA.

The radically free ethylenically unsaturated polymerizable polysiloxanes, including especially the oligomers and the acrylated polysiloxane polymers and which; It contains pendant acrylic or methacrylate telechelic and / or acrylic groups, are also examples of radically free polymerizable oligomers useful in the polymerizable compositions of the invention. These (meth) acrylated polysiloxane oligomers can be prepared following a wide variety of methods, generally by the reaction of chloro-, silanol-, aminoalkyl-, epoxyalkyl-, hydroxyalkyl-, vinyl-, or hydrurofunctional silicon polysiloxanes. with a corresponding functional (meth) acrylate terminating agent. These preparations are reviewed in a chapter entitled "Photopolymerizable Silicone Monomers, Oligmers, and Resins", by A. F. Jacobine and S. T. Nakos in Radiation Curing Science and Technology (1992), Plenum: New York, pages 200-214. Preferred acrylated polysiloxane oligomers include acrylyl-modified polydimethylsiloxane resins, marketed by Goldschmidt under the name TEGO RC and those monofunctional and difunctional polysiloxanes terminated in acrylamide which are described in US Pat. UUUU. No. 5, 091, 483 (Mazurek et al).

When a radiation-activatable crosslinking linker is present in a coating material that is polymeric, as opposed to a monomeric or oligomeric, the polymers that are preferred have extractable hydrogen atoms in their main structure and / or the side chains of the polymer in a sufficient amount for. allow the crosslinking of the polymer at the desired level with exposure of the agent / composition of the crosslinking polymer to the source of monochromatic radiation. As a general rule, it is easier to extract hydrogen atoms from tertiary carbon atoms, from the allylic and benzylic groups, of these hydrogens at the carbon atoms in an alpha position with respect to an oxygen or nitrogen atom (e.g., ethers) and organic tertiary amines) and those carried by pendant or terminal mercapto groups.

The polymer that can be crosslinked by radiation can 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, or it can be a copolymer comprising the general polymerization product minus one of the monomers from which the aforementioned polymers and a copolymerizable comonomer can be derived. Alternatively, the radiation-bondable polymer can be an elastomer, such as those selected from the group consisting of polyurethanes, polydiorganosiloxanes, block copolymers of type A-B-A, synthetic rubber, poly (vinyl ethers), poly (vinyl esters), polyacrylates, polymethacrylates, or a copolymer comprising the polymerization product of at least one of the monomers from which the polymers mentioned above and a copolymerizable comonomer can be derived. In any case, it is preferred that the polymer that can be crosslinked by radiation (excluding the crosslinking agent) substantially does not absorb the radiation emitted by the monochromatic radiation source.

According to one embodiment of the invention, a photoinitiator or a suitable mixture of photoinitiators is selected in such a way that the initiator or mixture of initiators has an extinction coefficient greater than or equal to 1000 M "approximately 1 cm" 1 in the Peak wavelength of the chosen monochromatic radiation source. Such choice guarantees an effective use of the radiation to cure the polymerizable composition to a well defined depth which will depend on the concentration of the photoinitiator. Typically, these combinations of initiator and radiation source will efficiently polymerize the polymerizable composition to a depth of less than about 50 microns. Although, longer exposure times will allow a deeper healing to be achieved, efficiency will be drastically reduced. Alternatively, lower concentrations of the initiator can be employed with the given monochromatic light source, which allows deeper healing to be achieved, but resulting in the reduction of the cure rate and healing efficiency.

Suitable photoinitiators can be organic, organometallic or inorganic compounds, but, more commonly, organic in nature. Examples of commonly used organic photoinitiators include benzoin and its derivatives, benzyl ketals, acetophenone, acetophenone derivatives, anthraquinones, anthraquinone derivatives, benzophenone, benzophenone derivatives and triazine derivatives.

While the molar absorption capacity of the photoinitiator varies according to the wavelength, it is preferred that the photoinitiator for a given monochromatic source is selected such that the molar absorption capacity of the photoinitiator at the peak wavelength of the source is greater than 1000 M "1 c" 1 approximately, preferably greater than 5000 M-1 cm "1, and more preferably greater than 10,000 M" 1 cm "approximately 1. As an example, when a xenon chloride excitation lamp is selected, as the monochromatic light source for polymerizing a polymerizable composition, preferred photoinitiators include 2-methyl-l- [4- (methylthio) phenyl] -2-morpholinopropanone-1 with a molar absorption capacity of about 16,000 M "1 cm "1, and 4, 4 '-bis (4-isopropylphenoxy) benzophenone with a molar absorption capacity of about 10,000 M" 1 cm "1 to 308 nm, respectively.

The initiator or the chosen primer mixture can be added with the monomer mixture and / or radically free, ethylenically unsaturated, polymerizable oligomers to form a polymerizable composition. The photoinitiator or the photoinitiator mixture is to be used in an amount sufficient to provide the desired degree of polymerization in the final polymerized composition, ie, in an "effective amount". The amount of the photoinitiator will depend on the molar absorption capacity of the photoinitiator at the peak wavelength of the source and the thickness of the coating and should be selected such that at least 2, preferably 5 and, more preferably, 10% of the total incident actinic radiation that reaches the coating is absorbed by the photoinitiator inside the coating. It will be understood that although a minimum absorption is required for efficiency, excessive absorption can cause a decrease in total efficiency. Preferably, the amount of the photoinitiator will be such that no more than 90, preferably no more than 80 and, more preferably, no more than 70% of the incident actinic radiation reaching the coating is absorbed by the photoinitiator within the covering. Generally, the initiator or the initiator mixture will constitute from a level as low as about 0.001 to about 7% of the weight of the polymerizable composition, preferably, from about 0.01 to about 5 percent, and more preferably from) around 0.1 to about 4 percent.

In another embodiment, the invention provides a source; monochromatic low input power to cure a polymerizable composition comprising monomer mixtures ?; and / or radically free, ethylenically unsaturated polymerizable oligomers, containing one or more photoinitiators. Sources that require less than about 10, preferably less than about 5, and more preferably less than about 3 W / cm of bulb length are useful in such methods. In general, the most useful low-power light source that is commercially available is the low-pressure mercury arc lamp (germicidal lamp) that has a radiation with a peak intensity centered around 254 nm, because of the existence of commercially available photoinitiators that are activated quickly at this wavelength. The use of a source of radiation powered with low power, such as the germicidal lamp, as a photopolymerization energy source, provides a highly efficient polymerization process d = in terms of energy when employed with such photoinitiators; In general, these sources emit much less unwanted radiation in the form of heat and are commercially available at low cost. Such lamps in said systems can also be arranged sequentially in a row, also at a low cost and with little excess heat. Therefore, these lamps can be used to provide a band of narrow wavelength radiation that interacts very efficiently with a photoinitiator selected in such a way as to offer an economical, energy efficient alternative to conventional photopolymerization methods in tramada form.

Similarly, a further embodiment uses a low power monochromatic light source to lattice a crosslinkable polymer in a reticular manner by radiation. A preferred light source is a low pressure mercury arc lamp with a peak wavelength of 254 nm.

In addition to the radiation-bondable polymer, the compositions that are employed in one aspect of the invention include a crosslinking agent that can be activated by radiation of the copolymerizable or non-copolymerizable type, although the latter is preferred. P02: Generally, the radiation-binding agents that can be activated by radiation, useful in the invention, are those that become hydrogen extractors after absorbing light with a wavelength comprised between approximately 230 and 330 nm.

The crosslinkable copolymerizable agents that can be activated by radiation are randomly incorporated into the main structure of the polymer crosslinkable by radiation during the polymerization of the polymer. As a result, the copolymerizable crosslinking agent must be compatible and miscible with the monomers from which the polymer is derived (ie, there must be no abrupt phase separation with the mixture).

The copolymerizable crosslinking agents tend to promote a more efficient cross linkage than their non-copolymerizable counterparts and minimize the issues associated with the volatility of the crosslinking agent.

Useful copolymerizable crosslinking agents include substituted anthraquinones, copolymerizable acetophenones, copolymerizable benzophenones, substituted triazines, and mixtures thereof. The copolymerizable crosslinking agents useful in the invention can be found in US Pat. UU Nos. 4, 737, 559 (Kellen et al); , 073, 611 (Boettcher et al); 5, about 28, 386 (Auchter et al); 5, 202, 483 (Bott et al); 5, 248, 805 (Boettcher et al); , 294, 688 (Auchter et al); and 5, 389, 699 (Boettcher et al). Preferred copolymerizable network bonding agents are acrylate functional aromatic ketones which are presented in US Pat. UU No. 4, 737, 55S1 (Kellen et al), in particular 4-acryloxybenzophenone.

The non-copolymerizable crosslinking agents which can be activated by radiation are mixed or reacted with the crosslinkable polymer by radiation after the polymerization of the polymer, or are mixed with the monomer (s) for the polymer before the polymerization. polymerization, but, in this case, do not react with the monomers. Within this class are the agents of: multifunctional reticular bond and graft-bonding crosslinking agents. One of the advantages associated with the use of non-copolymerizable crosslinking agents that are more versatile because they are added to the polymer after polymerization. Additionally, the non-copolymerizable type does not need to be miscible, compatible or reactive with the monomers from which the polymer is to be derived.

Preferred non-copolymerizable crosslinking agents are the anthraquinones, substituted anthraquinones, multifunctional acetophenones, substituted triazines and mixtures thereof. Specific examples of non-copolymerizable crosslinking agents of the anthraquinone type are the anthraquinones, t-butyl anthraquinone and 2-ethyl anthraquinone. Particularly preferred non-copolymerizable network bonding agents that can be activated by radiation are acetophenones and multifunctional benzophenones of the following formula: Wherein: X represents CH3-; 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 which are also free of esters, triols, allylic groups and benzylic groups with atoms of hydrogen not accessible intramolecularly for the carbonyl group in formula II; and n represents an integer of Z or greater part, preferably of 2-6.

In a particularly preferred embodiment, X is phenyl; W is oxygen; Z is - (-CH2- (2-? 2-; and n is 2.

Specific examples of the preferred multifunctional benzophenones include 1, 5-bis (4-benzoylphenoxy) pentane, 1, 9-bis (4-benzoylphenoxy) nonane and 1,11-bis (4-benzoylphenoxy) undecane.

Useful non-copolymerizable crosslinking agents of substituted triazine are also disclosed in US Pat. UU Nos. 4, 329, 384 (Vesley et al); 4, 330, 590 (Vesley). Specific examples of substituted triazine linker bonding agents include 2,4-bistrichloromethyl-67- (4-methoxyphenyl) -s-triazine, 2,4-bistrichloro-methyl-6- (4-methylphenyl) -s-triazine and 2,4-bistrichloromethyl-6- (phenyl) -s-triazine.

The crosslinking agent that can be activated by radiation is employed in an effective amount, by which is meant that it is an amount large enough to provide the desired final properties. For example, within the context of the manufacture of an adhesive, an effective amount of the crosslinking agent is an amount sufficient to crosslink the polymer such that it has adequate cohesive strength, but not in as large a quantity as so that the polymer becomes overcrowded. The actual amount of the crosslinking agent that is used will vary depending on the application, the type of polymer, the type of crosslinking agent, the ease for extracting the nitrogen from the polymer, the reaction capacity of the formed radicals , of the intensity and time of exposure of the composition to the irradiation, of the molecular weight of the polymer and of the final properties desired for the material. Within these guidelines, the amount of the crosslinking agent that is employed is preferably between 0.01 and 1.0% of the weight of approximately, based on the total weight of the polymer.

When monochromatic sources are used to polymerize a polymerizable composition or to crosslink a polymeric coating, it is desirable to minimize competitive adsorption of species other than species that can be activated by radiation, including the radically free, polymerizable monomer, oligomer or polymer, and optional auxiliaries that may be present. For example, in a clear, polymerizable, free radical coating, containing a free radical photoinitiator cured using germicidal lamps, it is desirable to minimize the amount of aromatic groups that are not photoinitiators in the coating, since the aromatic groups have large Molar absorption capacities in the region of 254 nm, wavelength emitted by the source that will compete with the light provided by the source. It is preferred that any competing adsorption is such that it can represent less than about 50% of the total absorption through the coating, more preferably less than about 10%, and more preferably less than about 1%. .

The compositions that can be activated by radiation of the invention can be coated directly on a substrate and can be cured with exposure to the radiation source. The coatings can be applied to the substrate by any of a variety of conventional coating methods, such as by solvent or waterborne, but the methods that are preferred are those that are commonly used for solid coatings at 100%. percent and include lamination coating, knife coating, curtain coating, polymerization coating, hot melt coating, direct and offset gravure coating, matrix coating, and any other coating method. coating that may be useful as is known to all those skilled in the art. In general, the most useful coating methods will be those that are specifically adapted to provide thin coatings, preferably by means of the use of precision lamination and electrospray coating methods and the like, which include. those described in the US patents. UU Nos. 4, 748, 043 and 5, 326, 598 (both by Seaver et al). When the viscosity of a coating formulation is not suitable for a preferred coating method, the coating composition can be heated to reduce its viscosity or, conveniently, can be diluted with a low viscosity diluent that can be a thinner. reagent such as, for example, a copolymerizable monomer, or a non-reactive diluent that is preferably removed before curing the composition using conventional drying techniques.

The compositions that can be activated by radiation can be applied on at least a part, at least, a significant surface of a suitable flexible or rigid substrate, or on a surface or support, which can be irradiated using the prescribed light sources. The 5 useful flexible substrates include paper, plastic films such as poly (propylene), poly (ethylene), poly (vinyl chloride), poly (tetrafluoroethylene), polyester (for example, poly (ethylene terephthalate)), a polyamide film such as a KAPTON film sold by DuPont, cellulose acetate and ethyl cellulose. A particularly useful substrate is oriented or non-oriented polypropylene. The supports can also be woven fabric formed by strands of synthetic fibers with mixtures of them or non-woven sheets. In addition, suitable supports include metal films, metallized polymeric films or ceramic sheet material. Additionally, suitable supports include substrates that are reflective or transparent and that are clear, colored, opaque or printed. One of the advantages of using the light sources of the present invention is the ability to use such low heat sources with polymerizable or crosslinkable coatings by radiation on heat sensitive substrates. The radiation sources that are commonly used often generate unwanted levels of thermal radiation that can distort or damage a wide variety of synthetic or natural flexible substrates. Suitable rigid substrates include, but are not limited to, glass, wood, metals, treated metals (for example those comprising automobile and boat surfaces), surfaces of polymeric material and composite materials such as fiber-reinforced plastics. It is possible to use suitable substrates without any surface modification or these can be treated by resorting to a large number of means well known to all those skilled in the art, which include corona treatment, flame treatment, chemical treatment, mechanical chemical attack, exposure to ultraviolet light, et cetera.

A particularly useful coating, derived from the method of the present invention, comprises the polymerization of acrylated polysiloxanes on a variety of substrates to form release coatings in a low oxygen atmosphere. The use of silicon release coatings has been a standard for the. industry for many years and is something widely used by the coatings suppliers and by the; manufacturers of large integrated tapes. The release coatings prepared in this way can have any type of release level desired, including: (1) premium or easy detachment, (2) moderate or controlled detachment, or (3) poor detachment; the premium detachment requires the least amount of force. Discoveries with premium release (ie, release coatings with aged release strength within a range above about 1.6 N / dm) are typically used in the release coating applications. However, premium release coatings are less useful, when they are used to coat the back surface with pressure sensitive adhesive tapes, since their low release force can cause tape roll instability and handling problems. Frequently reference is made to said release coating on the back surface of a construction of pressure sensitive adhesive tapes as "low adhesion load" (LAB). Release coatings with moderate to high levels of aged release (from 2 to 35 N / dm, approximately) are particularly useful when used as a low adhesion filler.

Polymerizable polysiloxane compositions suitable for the use of the invention for the purpose of producing release coatings are sold by, for example, Goldschmidt Chemical Corporation under the name TEGO. These acrylated polysiloxane resins can be poured and mixed to obtain optimized properties, such as the level of release, adhesive compatibility and substrate compatibility. An example of a mix that is recommended to achieve a premium (easy) release is a 70: 30 mix of TEGO RC726 and TEGO RC711.

In addition, polymerizable compositions containing acrylated polysiloxanes for use in the production of release coatings may include, as polymerizable constituents, 100% acrylated polysiloxanes or, alternatively, may include radically free polymerizable diluents in addition to the acrylated polysiloxanes. Such polymerizable non-polysiloxane diluents can be used to modify the release properties of the coatings of the present invention and also to enhance the mechanical properties of the coating and to anchor the supports or substrates used in pressure-sensitive adhesive tapes or in constructions. linear detachments. Depending on the final properties desired in the polymerized release coatings, the radically free polysiloxane-free polymerizable diluents useful include the monofunctional, difunctional and polyfunctional monofunctional, vinylester and methacrylate monomers and oligomers discussed above. Preferably, difunctional and polyfunctional triacrylate and methacrylate monomers such as 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane diacrylate, pentaerythritol triacrylate, 1,2-ethanediol diacrylate, 1,12-dodecanediol triacrylate, are used. trimethylolpropane triacrylate, pentaerythritol tetracrylate, pentaerythritol pentacrylate and difunctional and polyfunctional acrylate and methacrylate oligomers including acrylated epoxy oligomers, acrylated aliphatic oligomers, acrylated urethane oligomers, acrylated polyester oligomers and acrylated polyester oligomers, such as those marketed by UCB Radcure Inc., under the trade designation of Ebecryl and by Sartomer, Exton, PA. The monofunctional, difunctional and polyfunctional monofunctional triacrylate, methacrylate and vinyl ester monomers used in these release coatings can be used at a concentration of about 10 to 99, and preferably 25 to 95%, of the weight , approximately, based on the total weight of the composition of the release coating. Mixtures of non-monofunctional, difunctional and polyfunctional polysiloxane monomers and oligomers can also be used.

The exposure times needed to cure acrylated polysiloxanes will depend on the reactivity of the particular formulation being used, the intensity of the monochromatic source and the molar adsorption capacity of the photoinitiator at the wavelength of the selected source. As the intensity of a given source decreases, longer exposure times are required. When operating activated monochromatic sources at input powers of 40 W / cm or more, the exposure times can be as short as 5 seconds, more preferably less than 1 second and, more preferably, less than about 0.1 seconds The use of lamps operated at a lower power than lamps with low pressure mercury arc, require longer exposure times. This can be achieved conveniently by using multiple lamps arranged in a configuration similar to a system.

A particularly useful second coating, derived from the method of the present invention, corresponds to the polymerization of monomers, oligomers or mixtures thereof, polyfunctional, to form hard coatings. Such coatings are well known in the art and can impart abrasion resistance, scratch resistance or usual wear resistance on the surface or substrate. Preferred compositions include those of two monomers, oligomers and mixtures of these, acrylate multifunctionals that were described above and include monomers such as 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, trimethylpropane triacrylate ,. pentaerythritol triacrylate, 1,2-ethanediol diacrylate, 1,12-dodecanediol diacrylate, trimethylpropane triacrylate ,. pentaerythritol tetracrylate and pentaerythritol. Also preferred are monomers with even greater functionality such as those described by Welding et al, in US Pat. UU No. 4, 262, 072. In addition, other benefits can be obtained through the addition of an auxiliary that is selected for its hardness such as a particular functionalized surface ceramic coating, as described by Bilkadi in US Pat. UU No. 4, 885, 332.

The lattice bond of the pressure sensitive adhesive coatings can be conveniently carried out using the present method. Preferred crosslinking agents include multifunctional benzophenones and copolymerizable benzophenones, such as acryloxybenzophenone.

The examples that follow are given to help understand the present invention and are not intended to be considered as limiting the approach thereof. Unless there is a contrary indication, all parts and percentages are given by weight.

EXAMPLES Test Method Loop Adhesive Tape Test: A qualitative cure measurement was provided by contacting a strip of approximately 10 cm of a tape coated with KRATON adhesive (Shell, Houston, TX) with a LAB of the polyurethane to provide an adhesive surface silicon free. The adhesive was applied to the surface of the already tested release coating and it was removed three times successively in three different places. Then the test tape was folded back on itself causing one surface of the adhesive to come into contact with the other adhesive surface. If the silicon surface cure was carried out properly, the adhesive surfaces were bonded together, resulting in the delamination of the adhesive from the tape backing when they came off. In the case of an unacceptable silicic transfer, the bond between the adhesive surfaces did not occur.

Adhesion and reattachment of the release: A sample of the release coating substrate was attached, face up using double bonding tape, to a standardized steel plate of 0.79 x 1.97 cm. The test tape of the standard adhesive e was laminated. KRATON base on the release coating using a mechanical roller with an applied force of 2 kg. The test strip was then peeled off from the surface with a release coating at 30.5 centimeters per minute and the peel force at 90 ° C was recorded. an INSTRON tension and compression tester. Adhesion of the adhesive was measured after removing the test tape from the silicone-coated surface, applying the test tape to a second standardized surface with an application force of 100 grams, and then the force required to remove the tape at a rate of 30.5 centimeters per minute was recorded.

Weight of the silicone coating: The weight of the silicone coating was measured using an X-ray fluorescence analyzer (model LAB X3000, Oxford Instruments, Abingdon, United Kingdom) (the direct readings were converted to the actual weights of the coating (g / m2)) by applying a correction factor provided by the manufacturer of acrylated polysiloxane to compensate for the variable amounts of silicon in the different formulations evaluated.

Silicone transfer: A KRATON-based test tape (Shell Oil Company, Houston, TX) was measured on the release coating before being rolled into a roll. The. Test tape used a silicone-free LAB to remove any contact with a silicone surface before testing. After allowing the test tape to be in contact with release coating for a minimum of one hour, the tape was removed and evaluated using electronic spectroscopy for chemical analysis (ESCA) using a start angle of 40 °. The intensity of the silicon ESCA signal was then evaluated. The value for a linked release coating was less than 5% of the atomic weight of silicon on the surface of the adhesive.

Delta Turbidity: A section of 9.8 by 9.8 centimeters was removed from the coated substrate that was to be analyzed and joined to a glass plate with a thickness of 0.32 cm using a standard adhesive tape. The turbidity was measured at four points of the sample using a colorimeter (model XL-385, BYK Gardner, Silver Springs, MD) and the average was reported as the value of the initial turbidity. The samples were then mounted, with the coating facing up, on a Taber abrasion gauge (model 5150, Taber Industries, North Tonawanda, NY) where they were subjected to wear using CS-10F wheels for 50 cycles with a load of 500 g. A cycle is equivalent to a complete revolution the sample. The turbidity was then measured as mentioned above and the difference between the initial and final turbidity as the turbidity Delta was reported.

Gel test: A guarded article coated with 3.2 x 3.2 cm adhesive was weighted, placed in a Maya basket and then immersed in a suitable solvent for a period of four hours. Then the basket was removed and the excess solvent was left drained by the Maya the residual gel was retained. The basket containing substrate and gel was dried for two hours at 60 ° C and reweighed. The amount of insoluble adhesive that remained in the basket was reported with a percentage of the initial adhesive coating present in the sample.

Example 1 This example describes the formation of a cured polysiloxane release coating using a bank of low pressure mercury arc lamps.

A 70: 30 mixture of TEGO RC726 (Goldschmidt) and TEGO RC711 containing 2% DAROCUR 1173 was coated.

(Ciba) on a crown-treated cast polypropylene substrate using a manual coater (Euclid Tool &Die, Bay City, MI). The weight of the coating was estimated at around 1 g / m2. Then it was placed as tape of the coated substrate on an open aluminum tray and passed through the outlet of a bank of silicone germicidal lamps (model G15T8, Osram Sylvania, Danvers, MA) mounted on the part that can be made inert of nitrogen a processor to the conveyor belt at a speed of 15.2 meters per minute. Oxygen levels were maintained below 50 ppm as measured using an oxygen analyzer (model FAH05005, Delta F Corp., Wobum, MA). The measurement of the average of the intensity of radiation and dose provided was 0.7 mW / cm2 and 1.75 mJ / cm2, respectively, using a UVIMAP model UM254L-S (Electronic Instrumentation and Technology, Sterling, VA). The coating was dry and cured, according to the loop adhesive tape test that was written before. A peeling force of 0.5 N / dm was measured.

Example 2 This example describes the preparation of a coating with average release properties.

The method of example one was repeated using a 45:55 mixture of TEGO RC726 and RC711 containing 2% DAROCUR 1173.

Again, the coating of the drying processor was removed and cured according to the loop adhesive tape test. The release adhesion was measured at 2 N / dm.

EXAMPLE 3 This example describes the curing of a low release formulations comprising a mixture of acrylated polysiloxanes with a silicone-free acrylate, cured using a xenon chloride excitation lamp.

A coating of 10 parts of TEGO RC711 and 90 parts of a polyethylene glycol diacrylate (400) (SR 344, Sartomer Corp.) containing 5% IRGACURE 907 (Ciba) was placed on a biaxially oriented polypropylene film ("BOPP") treated with a corona flame using the method of Example 1. The coated substrate was passed under a xenon chloride excitation lamp (model 308, Heraeus, Hanau, Germany) at a rate of 25 meters per minute using the inert nitrogen processor from example one. The measurements of the intensity of the source and the dose were from 28.7 m W / cm2 and 10. 0 mJ / cm2, respectively, using a UVIMAP (model UM313H-S, EIT). The coating was dry to the touch and proved to have an adhesion to the release of 14. 6 N / dm Example 4. This example describes the use of a transparent top sheet to eliminate the need to purge the nitrogen part the method of example two was repeated using the BOPP film treated with fires with a transmission of approximately 85% at 254 nm as a sheet coated The transformation in nitrogen to inert was not used. The cured coating presented some confusion of linings when the substrate and the topsheet were examined, but it was clearly indicated that a top sheet can provide a sufficient barrier to the oxygen in order to allow curing to occur and coatings to be cured. irradiation of the prelate of the support, that is to say, the exhibition through a support.

Example 5. This example describes the high continuous rate of curing of a release coating of acrylated polysiloxanes, like an exciter lamp.

It was coated with a 45: 55 mixture of TEGO RC726 and RC711 containing 2% IRGACURE 907 continuously on a crown-treated cast polypropylene Maya, using an offset engraving coating. The Maya was passed through a nitrogen chamber of inert curing with less than 50 ppm of oxygen at 450 meters per minute, where it was exposed to the output of a xenon chloride exciter lamp (Heraeus) was the maximum power. A quartz plate supplied a window between the lamp and the part of the inert chamber. The cured release coatings were analyzed for adhesion and re-adhesion of the release after 24 hours and one week of aging at 120 ° C and at 120 ° C with a relative humidity of 90%. The test data with the use of SCOTCH tape (3M Company, St. Paul, MN) 810 Magic Tape are presented in Table 1. Re-additions were measured for glass. Table 1 Examples 6-8 These examples demonstrate the low transfer of silicone to the adhesive of an adhesive coated article in which the LAB provides poor release and is a cured acrylated polysiloxane coating using a plurality of low pressure mercury arc lamps.

A coating comprising 45 parts of TEHGO RC706 and 55 parts of TEGO RC711 and varying amounts of DACOUR 1173 as a photoinitiator was applied on one side of a cast polypropylene substrate using a five roll receiver. A coating weight of 0.7 g / m2 was chosen. The coatings were cured at 36.6 meters per minute using a total of 18 G15T8 lamps giving a dose of 2.0 mJ / cm2, a viscous KRATON adhesive on the opposite side was hot-melt coated on the opposite side and the construction was rolled up. After allowing a residence time of several days, the samples were removed from the roll and ESCA measurements were made on the surface of the adhesive. The data are presented in table 2.

Table 2 Examples 9-11 These examples demonstrate the low transfer of silicone to the adhesive of an adhesive coated article in which the LAB provides the release and is a cured acrylated polysiloxane coating using a plurality of low pressure mercury arc lamps.

A coating comprising 17.5 parts of TEGO RC726, 35 parts of TEGO RC706, and 47.5 parts of TEGO RC711 was applied, with 3 percent of DARCOUR 1173 as photoinitiator on one side of a cast polypropylene substrate using a five-roll receiver . A coating weight of 0.7 g / m2 was chosen. The coatings went to 36.6 meters per minute using three different levels of light provided by 6, 18, or 30 lamps with low pressure mercury arc G15T8. A viscous KRATON adhesive was coated on the hot melt line on the opposite face and the construction was rolled up. After allowing a residence time of several doses, the samples were removed from the roller and ESCA measurements were made on the surface of the adhesive. The data is presented in table 3.

Table 3 Examples 12-19 These examples describe the high continuous rate of curing of an acrylated polysiloxane coating using a low pressure mercury arc lamp system.

A 70:30 mixture of TEGO RC715 (Goldschmidt) and RC711 containing two percent DAROCUR 1173 was coated continuously on a BOPP film treated in a uniform crown using the coating method of Example 5. The coated film was coated. through an inert-curing nitrogen chamber with an oxygen content of less than 50 ppm. A clear polyethylene film (transmitted at 253 nm> 82 percent) isolated the mobile mesh from a three meter long bank of 69 G15T8 germicidal lamps distributed across the mesh. Different mesh speeds were run, the results of which are presented in table 4. Table 4 Example 20 This example describes the continuous preparation of a pressure sensitive adhesive tape in which the LAB is cured.

It was coated with a 45:55 mixture of TEGO RC706 and RC711 containing two percent DAROCUR 1173 textured textured polypropylene mesh with a coating weight of 0.7 g / m2 using a five roll coater. The wet coating was cured at 36.6 meters per minute in an inert curing nitrogen chamber by exposing it to a three meter long bench of 24 lamps with low pressure mercury arc (model G25T8, Osram Sylvania). The average intensity was 4.04 mW / cm2 and the. The dose delivered was 6.7 mJ / cm2. It was coated with an adhesive which can be hot-melt coated, the face uncoated and the mesh was wound on a continuous roll.

Examples 21-25 These examples describe the use of the present invention to prepare release coatings. The data also indicate the performance of coatings cured with aging.

It was coated with various mixtures of RC901 (Goldschmidt) and RC711 containing two percent DAROCUR 1173 using the method of Example 1 on PE-PP copolymer sheets cut from a film that had been corona treated to provide a surface energy of 36-38 dynes / cm2. The coated substrates were then passed under a bank of 8 G15T8 bulbs at a rate of 15.2 meters per minute and subsequently an article coated with standard adhesive was laminated. The data for coatings cured before and after aging are presented in Table 5.

Table 5 EXAMPLE 26 This example describes the curing of a multifunctional acrylate resin using a xenon chloride excitation lamp in the absence of added heat and which serves to demonstrate the benefits of added heat when polymerized to obtain a hard coating.

A solution of hydantoin hexacrylate was applied at 30 percent MEK solids (as described in US Patent No. 4,262,072) containing four percent IRRACUITE 907 phr on a black polyester substrate. at 30.4 meters per minute and dry to obtain a dry coating with a weight of 25.8 g / m2. The viscous coating was then exposed at the outlet of a xenon chloride excitation lamp (Heraeus) at a rate of 15.2 meters per minute in an inert nitrogen chamber.

The final coating was dry to the touch and had a delta turbidity greater than 6.

Example 27 This example describes the effect of added heat in the curing of a multifunctional acrylate resin using a xenon chloride driving lamp.

Example 27 was repeated using the irradiating heater to preheat the coating to a temperature of 65. 6 ° C in the inlet opening of the curing chamber. The cured coating was dry to the touch, adherent and had a delta turbidity of less than 3 percent.

Example 28 This example describes the use of a low pressure mercury arc lamp system to cure a multifunctional acrylate to form a hard coating.

It was coated with a MEK solution containing 19 percent hexadecyte hydantoin solids containing 4 percent phr IRGACURE 184 a black, semitransparent polyester film, dyed and dried to produce a dry coating weighing 25.8 g / m2 . After that the film was cured at 33.5 meters per minute in a bank of 24 lamps with low pressure mercury arc G25T8, with an irradiance of 2.7 mW / cm2 and a total dose of 5.9 mJ / cm2. The oxygen content of the chamber was 12 ppm. The delta turbidity measurement was 4.1 percent.

Example 29 This example demonstrates the effect of heat when used with more lamps with low pressure mercury arc to cure hard coating compositions.

Example 28 was repeated using a solution with 9.2 percent solids. The coated film was passed with a dry queen weight of 14.8 g / m2 by an electrically heated roller to raise the mesh temperature to 66.7 ° C before entering the inert-curing chamber. The oxygen levels within the curing chamber were maintained between 20 and 40 ppm using a purge of nitrogen gas previously heated to an elevated temperature to increase the ambient environment within the curing chamber to a temperature of 62.2 ° C. The coating was cured at a speed of 36.6 meters per minute with an irradiance of 4.1 mW / cm2 and a dose of 8.2 mJ / cm2. The delta turbidity was 2.1 percent.

Example 30 This example describes the use of a radically free polymerizable formulation containing a copolymerizable ceramic particulate to form a hard coating.

A solution with 46 percent solids, in a 94: 6 ratio of i-propyl alcohol, was coated on a surface functionalized ceramic copolymerizable coating (which is described in US Pat. No. 4). , 885, 332) containing 4 percent phr IRGACURE 184 and dried on a semitransparent black polyester film, dyed with a dry coating weight of 25.2 g / m2. The viscous coating was cured as in Example 30 at a rate of 40.2 meters per minute, with an irradiance of 2.7 mW / cm2 and with a dose of 3.7 mJ / cm2.

The delta turbidity of the cured hard coating was 3.0 percent.

Example 31 This example shows the effect of the change in line speeds in the coating of example 30.

Example 30 was repeated, but with a line speed of 32.9 meters per minute. The delta turbidity measurement was 2.3 percent.

Example 32-35 These examples describe the use of a medium pressure mercury arc lamp to lattice a hot-melt adhesive containing acryloxybenzophenone.

It was coated with an acrylic hot-melt acrylic adhesive containing 0.1% acryloxybenzophenone, a paper-bearing mesh, and exposed to a medium-pressure mercury-arc lamp operated by microwave) model F300, UV Fusion -Systems , Gaithersburg, MD). Table 6 reports: gels with various dosages of UVC (250-260 nm) after 24 hours in ethyl acetate, according to Power Puck (EIT) measurements. The source provides a significant UVA (320-390 nm), a UVB (320-380 nm) and heat, in addition to UVC radiation. Table 6 Examples 36-39 These examples describe the use of a low pressure mercury arc lamp to lattice a hot-melt adhesive containing acryloxobenzophenone.

The method of Examples 32-35 was repeated using a bank of 9 lamps with low pressure mercury arc. The line speeds were adjusted to allow UV doses comparable to those of Examples 32-35 to be provided. The results of the gel and the UVC dosages are listed in table 7. The data show that gels can be obtained with identical percentages. The amounts of UVA, UVB and heat provided are negligible.

Table 7 Various modifications and alterations of the present invention will become apparent to all those skilled in the art, without departing from the focus and spirit of this invention, and it will be understood that the present invention is not limited to the illustrative modalities set forth in I presented.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property.

Claims (15)

Claims

1. A polymerization process characterized in that it comprises the steps of: a) providing a substrate coated on at least one of its parts with a mixture of a radiation-polymerizable composition comprising (i) a monomer, or oligomer, or a a mixture of the same, polymerizable, radically free, ethylenically unsaturated, and, (ii) a free radical photoinitiator; b) providing a source of essentially monochromatic radiation with an effective wavelength to activate said photoinitiator; and c) exposing the radiation-polymerizable composition to the radiation emitted by the radiation source for a sufficient time to polymerize the composition; wherein the photoinitiator and the wavelength of the radiation source are selected such that the extinction coefficient of the photoinitiator at the peak wavelength of the source is greater than about 1000 M "1 cm" 1 and, where the photoinitiator it absorbs at least 2 percent of the actinic radiation emitted by the source incident on the coating.

2. The method according to claim 1 ,. characterized in that said photoinitiator absorbs at least 5 percent of the actinic radiation emitted by the incident source on the coating.

3. A polymerization process characterized in that it comprises the steps of: a) providing a mobile substrate coated on at least some of its parts with a radiation-polymerizable composition comprising: (i) a monomer, an oligomer, or a. a mixture of the same, polymerizable, radically free, ethylenically unsaturated, and; (ii) a free radical photoinitiator; b) providing a source of essentially monochromatic radiation comprising one or more lamps, in which each of the lamps has an input power of less than about 10 W / cm, and with an effective wavelength to activate the said photoinitiator; and c) exposing the radiation-polymerizable composition to the radiation emitted by the radiation source for a sufficient time to polymerize the composition;

4. The method according to claim 3, characterized in that the peak wavelength of said monochromatic radiation is less than about 330 nm.

5. The method of claim 3, characterized in that the peak wavelength of said monochromatic radiation ranges from about 250 nm to about 260 nm.

6. The process of claim 3, 4, or 5, characterized in that said polymerizable composition comprises hydantoin hexacrylate or a copolymerizable ceramic particulate material;

7. The process of any of the preceding claims, characterized in that said polymerizable composition comprises one or more polymerizable, radically free, ethylenically unsaturated monomers of the formula: [A] mB wherein: A represents a reactive, radically free, ethylenically unsaturated functional group; m is a number equal to at least one; and B represents a m-radical that is free of aromatic, chloro-, and other portions or substituents that absorb radiation significantly at the wavelength of the monochromatic radiation source.

8. The process of any of the preceding claims, characterized in that said polymerizable composition comprises one or more polymerizable, radically free, ethylenically unsaturated polysiloxanes or comprises one or more acrylated polysiloxanes.

9. The method of any of the preceding claims, characterized in that it comprises the step of heating the coated substrate.

10. The method of any of the preceding claims, characterized in that the radiation source comprises at least one low pressure mercury lamp.

11. A method for lattically bonding a polymeric coating, characterized in that it comprises: a) providing a mobile substrate coated on at least some of its parts with a crosslinkable composition comprising: (i) a polymer that can be crosslinked by radiation which contains extractable hydrogen atoms, and; (ii) a crosslinking agent that can; activated by radiation; b) providing an essentially monochromatic radiation source comprising one or more lamps, in which-each of the lamps has an input power of less than about 10 W / cm, and with an effective wavelength to activate the crosslinking agent and to crosslink the polymer; and c) exposing the radiation-bondable composition to the radiation emitted by the monochromatic source for a sufficient time to lattice the polymer;

12. The method according to claim 11, characterized in that: said polymer crosslinkable by radiation is a thermoplastic polymer that is 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 of the monomers from which the aforementioned polymers can be derived and their copolymerizable comonomer; or is an elastomer which is selected from the group consisting of polyurethanes, polydiorganosiloxanes, block copolymers, synthetic rubber, natural rubber, ethylene-vinyl monomeric polymers, poly (vinyl ethers), poly (vinyl esters), polyacrylates, polymethacrylates and copolymers which they comprise the polymerization product of at least one of the monomers from which the aforementioned polymers and a copolymerizable comonomer can be derived; and said crosslinking agent that can be activated by radiation is selected from the group consisting of anthraquinone, substituted anthraquinones, multifunctional acetophenones, monofunctional benzophenone, substituted triazines and mixtures thereof.

13. The method of any of the preceding claims, characterized in that the substrate comprises a polyolefin film.

14. A coated substrate made following the method according to any of the preceding claims.

15. A substrate coated with a pressure sensitive aggressive made following process of claims 11, 12 or 13. Summary In one aspect, the invention provides a method for polymerization efficient in terms of energy comprising irradiating a polymerizable composition and a photoinitiator with a strong, essentially monochromatic radiation, in which the photoinitiator and the wavelength of the strong radiation are selected from such that the extinction coefficient of the photoinitiator at the peak wavelength of the source is greater than about 1000 M "1 cm" 1, and such that the photoinitiator absorbs at least 2% of the incident actinic radiation on coating. In another aspect, the invention provides energy-efficient methods for the polymerization of polymerizable compositions and for crosslinking the crosslinkable compositions by irradiating the respective compositions with strong, essentially monochromatic, low-potency radiation. These low power power sources have an input power of less than approximately 10 W / cm. Articles made from the aforementioned methods are also provided, including polymeric films with release coatings, adhesive coatings, hard coatings and the like.