MXPA98003462A - Termoactive composition adhesive - Google Patents

Abstract

A heat-activatable adhesive containing an acrylic copolymer, which comprises a monomer consisting of an acrylate or methacrylate ester of a non-tertiary alkyl alcohol having a Tv of about 0 ° C or less, a monomer consisting of an acrylate ester or methacrylate of an alcohol having a TV of at least about 50 ° C, and a functional monomer. The selected embodiments include a retroreflective article comprising a film having a substantially planar surface and a structured surface, the structured surface comprising a plurality of accurately formed projections, a colored layer deposited on the structured surface and adhered to it in a plurality of discrete places, and a layer of thermoactivable adhesive placed on the layer colors

Description

THERMORATIVE ADHESIVE COMPOSITION DESCRIPTION OF THE INVENTION The invention relates to a thermoactivatable adhesive, acrylic, crosslinked, with low activation temperature, and products containing such an adhesive. Most retroreflective coatings containing embedded lenses and encapsulated lenses, in particular for the Japanese traffic signal market, are heat-applicable coatings having a heat-activatable adhesive. However, cubic corner retro-reflective coatings typically only adhere through the use of pressure sensitive adhesives, which are substantially different from heat-activatable adhesives. See, for example, Adhesion and the Formulation of Adhesives 2d Ed., Wa e, pp. 98-99 (Elsevier Applied Science Publishers 1986). The cubic corners retroreflective coatings applicable by heat could be advantageous since they could have better handling characteristics, better quality and easy maintenance. A heat-applicable cubic corner retro-reflective coating could have the desired optical clarity; having the desired level of adhesion, so that the coating is preferably positionable, but is not slid on the substrate once fixed in position; have the ability to be applied at approximately 70 ° C or less, by means of a thermal lamp vacuum applicator ("HLVA") without losing its optical quality; strongly adhere without any delamination or failure by "detachment"; and be applicable to curved edge substrates such as aluminum panels used for Japanese regulated road signs. Adhesives comprising nitrile rubber and an acrylic polymer, described in Japanese Published Kokai Patent No. 88056274-B, are the thermo-active adhesives currently employed to adhere retro-reflective coatings to aluminum substrates in the Japanese traffic signal market. However, if this type of adhesive is applied to a cubic corner retroreflective coating, the whiteness of the coating typically decreases because the color of the adhesive is dark brown and the coating is translucent. In addition, when the prior art heat-activatable adhesives are laminated to a cube corner retroreflective coating wherein the coating sealant film has a surface treatment such as a corona or chemical primer, the coating can not be retained on curved edge substrates. due to its low cohesiveness at elevated temperatures. Because the activation temperature of the current heat-activatable adhesives is relatively high (from about 82 ° to 93 ° C), the brilliance of the coating typically decreases due to the thermal distortion of these retroreflective elements. Also, thermoactivatable adhesives based on nitrile rubber have little or no adhesion at room temperature. As a result, they are not suitable for adhering cubic corner retro-reflective coatings to aluminum due to the displacement of the coating prior to processing with HLVA. A cubic corner retroreflective cladding applicable by pressure is not easily positionable because most pressure sensitive adhesives have a very early initial adhesion. Because the adhesive typically fails cohesively after application, the coating can be applied only to curved substrates having a radius of 127 millimeters ("mm") or greater. Such adhesives can not be maintained on the curved edges of regulatory guide signals in the Japanese traffic signal market, which typically have a radius of 7 to 8 mm. In addition, coatings applied using pressure sensitive adhesives tend to trap air between the substrate and the coating during signal fabrication, so that waste is typically high.

They need to satisfy similar requirements paca Lia of movies or r < * piti? i-ia? tp. * pptfífúal cpticsnapte clear to traffic signs, Dinoc products and film lamination to handle light to clear glass or plastic surfaces. Filming films (surface) typically must be laminated to their substrates without entrapping air bubbles and without interfering with the optical characteristics of the product. Such films typically provide unique properties such as stain resistance, water resistance and the like. Light-handling products, such as brightness-feeding films, light-controlling films and private films for computer or monitor screens can be considered as special examples of coating films where the main function is to control the optical properties of the product . Decorative films, such as for tiles, tables and backs, also make use of cover films. In such decorative films, the ease of application, including the ability to position and the ability to be attached to the substrate without entrapping air bubbles are considered important. Pressure sensitive adhesives and tapes currently produced by ultraviolet ("UV") polymerization do not meet all of the above requirements, especially with respect to adhesion, because the high adhesion of known pressure sensitive adhesives makes them difficult To put. The known heat-activatable adhesives often lack the combination of optical clarity, high cohesive strength and low activation temperature, which are critical for the lamination of microstructured surfaces such as those used in the retroreflective coating products of this invention. Acrylic adhesives employing isobornyl acrylate are described in "Japanese Published Kokai Patents Nos. 5 (1993) -310810 and 6 (1994) -128544, but these references do not teach or suggest their use for adhering retroreflective coatings to substrates. Acrylic adhesives employing N, N-dialkyl substituted amides are described in US 4,946,742, US 5,334,686 and EP 615 983 A2, although some of them describe pressure sensitive adhesives for the application of PVC, none describe thermoactivatable and optically clear adhesives. used for the application of coating products There is a need for improved thermoactivatable adhesives for the adhesion of the coating to the desired substrates There is also a need for heat-applicable coating products that can be used, for example, to increase the brilliance, control the light, help maintain the privacy of a computer screen, and improve the appearance of substrates, or create reflective areas on clothing or other items to improve user visibility. The present invention provides a heat-activatable adhesive composition comprising an acrylic copolymer, the copolymer comprising: (a) about 10 to 85% by weight based on the weight of the monomer of a monomer consisting of an acrylate or methacrylate ester of an alcohol non-tertiary alkyl having a Tv of about 0 ° C or less; (b) about 10 to 70% by weight based on the monomer weight of a monomer consisting of an acrylate or methacrylate ester of a non-tertiary alkyl alcohol having a Tv of at least about 50 ° C; and (c) about 5 to 50% by weight based on the weight of the monomer of a functional monomer. The present invention also provides retroreflective articles having on the back surface, that is, where light does not collide, thereof a thermoactivable adhesive at low temperature. The invention also provides light controlling and optically clear coating films having a low temperature heat activatable adhesive on at least one surface. The adhesive of the invention has high transparency both after application and after aging, excellent resistance to cohesion, aita adhesion to polar substrates such as aluminum, glass, PVC, PMMA and stainless steel, and is obtained from a process without solvents. The retroreflective articles of the invention comprise, in this order, a reverse reflective coating having a substantially planar surface and a structured surface, the structured surface comprised of a plurality of precisely formed projections such as cube-corner elements, a colored thermoplastic layer, placed over the surface structured and adhered to it in a plurality of discrete locations, and a layer of heat-activatable adhesive placed on the colored thermoplastic layer. The thermoactivatable adhesive layer may comprise a crosslinked acrylic polymer having an elastic modulus (measured by means of a thermal, mechanical, dynamic analyzer, 6.28 rad / second, compression mode) ranging from about 5 x 106 to about 1 x 108 dyne / square centimeter (din / cm2) at 30 ° C, and preferably ranging from about 5.0 x 105 to about 1.0 x 107 din / crn2 at 70 ° C. The invention further provides articles having decorative and optical properties that contain the heat-activatable adhesive of the invention.

The coating film of the present invention is used to provide a barrier to prevent foreign materials such as organic solvents, water, dust, oil, earth, etc. from attacking the retroreflective film, for example, cubic corners. The film can also be used to protect various surfaces and substrates against vandalism such as * graffiti *. In this way, the polymeric materials used in the coating film should generally be resistant to environmental degradation (eg, heat, UV light) and chemical attack, so that the retroreflective coating can be used for outdoor applications. generally in the long term. Polymeric materials should also have good adhesion to the cubic corner layer and ink. The adhesives of this invention meet the market requirements of Japanese traffic signals, that is, they have high transparency both initially and after aging; adhesion at appropriate initial room temperature to place the coating, high adhesion to aluminum, stainless steel and other coating substrates; low activation temperature (no more than about 70 ° C); they do not decrease the retroreflective brilliance of the retroreflective coating, and exhibit excellent cohesion resistance to maintain the coating on curved substrates. The combinations of all these properties are difficult but not impossible to obtain heat-activated adhesives based on solvent. However, the adhesives of the invention are advantageous from the point of view of environmental problems because they can be made by a process without solvent. The cubic corner retroreflective coatings, heat applied, light controlling films, coating layer, and others of the invention can be easily applied to permanently trap air. The retroreflective articles provide excellent adhesion to rounded-edge substrates such as those used in Japanese regulated road signs, as well as to severely curved substrates useful in the zonal market of construction work. The invention will be better explained with reference to the drawings, in which: Figure 1 is a cross-sectional view of a retroreflective cladding article made in accordance with the present invention. Figure 2 is a perspective view of a signaling article made in accordance with the present invention, which also schematically illustrates the rounded edge test. 1U Figure 3 is a cross-sectional view of a retroreflective coating for traffic control with a coating film made in accordance with the present invention. Figures 4 and 5 are cross-sectional views of graphic and / or decorative coatings made according to the invention. These figures, which are ideal, are not scaled and are intended to be merely illustrative and not limiting.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES OF THE INVENTION An illustrative retroreflective article of the present invention is shown (in enlarged cross section) in Figure 1. The cover film 1 is preferably placed on a flat, smooth surface of the layer 2, the combination of the coating 1 and layer 2 is they refer as a structured coating 7. The colored sealing film 3 is placed on the back or structured surface of the layer 2, and empty volumes 10 are defined between the cavities of layer 2 and the colored sealing film 3 to impart retroreflectivity to the Article. Sealing film 3 is preferably sealed to layer 2 in a network of interconnecting connections as described in US Pat. No. 4,025,159 (McGrath). In Figure 1, the reference number 4 denotes an optional chemical primer layer or a corona treatment layer placed on the surface of a colored sealing film 3. Chemical and / or physical priming is preferred, but not necessarily for the invention. The combination of layers consisting of the structured coating 7, the colored sealing film 3, and the printing layer and / or the treatment layer 4 was designated as "retroreflective coating" 8. Illustrative examples of primer layers include layers of materials that provide a strong bond between the sealing film 3 and the adhesive layer 5. In another illustrative embodiment, the sealing film 3 and / or the adhesive layer 5 can be treated superficially, for example by corona treatment, before being joined together. The layer 5 of a heat-activatable adhesive is placed on the surface of the primer layer or corona treatment layer 4 or directly on the sealing film 3 if no primer treatment was used. The liner 6 is preferably placed on the surface of the thermoactivatable adhesive layer 5 to protect its surface. A sheet or sheet having from 1 to 6 members described above is called aguí "thermoactivatable retroreflective coating". The adhesive of the invention of the articles of the invention, and the articles themselves will now be described in more detail.

I. Adhesive Tßrmoactivable Acrylic The heat-activatable adhesives of the present invention exhibit a transparency of at least 85 percent in terms of the value measured by the method described in the Examples of the following section. If the transparency of the adhesive is less than 85 percent, the color of the adhesive is visible through the sealing film and the structured surface portions of the article, and the appearance and visibility of the article is degraded. A preferred range of transparency is at least 88 percent and more preferably at least 90 percent, to improve the performance of the reflective coating. The glass transition temperature (Tv) of the polymers was calculated using the glass transition temperature of the homopolymers of each monomer and the weight fraction of the monomers, as shown in the following equation of Fox, TG, Bull Am. Phys. Soc. (Ser 2) 1: 123 (1956) 1 J 1 / TV = Wa / Tva + b / Tvb + c / Tvc wherein Tv, Tva, Tvb and Tvc designate the vitreous transition temperature (in ° K) of a terpolymer of monomers a, b and c, a homopolymer of monomer a, a homopolymer of monomer b, and a homopolymer of monomer c, respectively. Wa, W and Wc are the weight fractions of the monomers a, b, and c, respectively, where Wa + Wb + Wc = 1. For the purposes of this invention, the Tv of the heat-activatable adhesive is substantially equal to the Tv of the acrylic copolymer or terpolymer. To obtain the proper adhesion, the vitreous transition temperature of the heat-activatable adhesive must be increased to a value higher than that of the pressure-sensitive adhesives normally used. This can be achieved by the use of monomers, which have glass transition temperatures of the higher homopolymer; or changing the weight fractions of the monomeric components. The vitreous transition temperature of the adaesives useful in the present invention is from about 0 ° to 40 ° C. When the vitreous transition temperature is less than about 0 ° C, the pre-adhesion adhesion tends to become excessively high, making placement and repositioning difficult. When it exceeds about 40 ° C, the pre-adhesion adhesion tends to become excessively low, making it difficult to keep the articles placed securely during activation by heat and bonding. In addition, the hot pressing temperature necessary to achieve a good bond tends to rise. The glass transition temperature of the adhesive is preferably from about 10 to 35 ° C and more preferably from about 15 to 30 ° C. When the glass transition temperature is within these ranges, the final bond at a lower hot pressing temperature becomes easier and at the same time, adhesion can be obtained within a suitable range. The adhesive value of the adhesive of the present invention is preferably from about 50 to about 1000 grams force / inch ("gf / inch") in terms of the value of the "pre-adhesion test" which is also described in FIG. Examples section, and more preferably is from about 500 to about 950 gf / inch. The adhesives of the invention are comprised of three types of monomers: a low T acrylate monomer, a functional monomer, and a high T * acrylate monomer. The weight average molecular weight of the acrylic polymers is preferably within the range of 10,000 to 5,000,000 and particularly preferably within the range of 500,000 to 2,000,000. The acrylic copolymers useful in the adhesive of the invention comprise from about 10 to about 85% by weight based on the weight of the monomer, preferably from about 20 to about 70% by weight of at least one acrylate or methacrylate monomer of Low TV Larger amounts of this monomer in relation to the other comonomers will soften the thermoactivatable adhesive, while less than about 10% by weight of this monomer will significantly reduce or eliminate adhesion. Useful low Tv monomers include those selected from the group consisting of a monofunctional acrylate or methacrylate ester of a tertiary alkyl alcohol, the alkyl group of which comprises from 4 to 12 carbon atoms, and mixtures thereof. Such low Tv acrylate or methacrylate esters generally have, as homopolymers, glass transition temperatures less than about 0 ° C. The monomers of acrylate or methacrylate ester of Low tv include ethyl acrylate, n-butyl acrylate (BA), isobutyl acrylate, 2-methyl butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate, n-methacrylate, octyl, isooctyl acrylate (IOA), isooctyl methacrylate, isononyl acrylate, isodecyl acrylate and mixtures thereof. Particularly preferred low Tv acrylate monomers include isooctyl acrylate, n-butyl acrylate, 2-methyl butyl acrylate, 2-ethylhexyl acrylate, and mixtures thereof. The copolymers of the invention also contain at least one functional monomer useful for increasing specific adhesion to certain surfaces and increasing total adhesion. For example, acid functional monomers such as acrylic acid will increase adhesion to polar surfaces such as glass or metals, paint and to basic surfaces. Weakly basic monomers, such as N, N-dimethylacrylamide and N-vinylpyrrolidone, will increase adhesion to surfaces such as rigid and plasticized PVC and to acidic surfaces. Useful functional monomers include those containing polar functional groups, such as carboxylic, sulfonic and phosphoric acids, hydroxy groups, lactam and lactone groups; N-substituted amides, N-substituted amine, carbamates and the like. In general, the functional monomer may comprise from about 5 to 50% by weight based on the total weight of the copolymer monomer. 1 / Moderately basic functional monomers include the N, N-dialkyl substituted amides, and monomers which behave as N, N-dialkyl substituted amides. Examples include N, N-dimethyl acrylamide (NNDMA), N, N-dimethyl methacrylamide, N, N-diethiacriamide, N, N-diethyl methacrylamide, N-vinyl pyrrolidone (NVP), N-vinyl caprolactam and the like. Slightly basic copolymerizable monomers, such as N-octyl acrylamide, can be used in co-binning with a higher amount of moderately basic monomer. It was found that strongly basic monomers (monomers having non-sterically hindered tertiary amine end groups) such as N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropyl methacrylate, N, N-dimethylaminoethyl acrylate, N-acrylate, N-dimethylaminopropyl, and the like, are very basic when used as the sole basic monomer, the PVC is dehydrochlorinated after aging and therefore possibly shortens the service life of the fabric coated with PVC or other PVC components. If strongly basic monomers are employed, it is preferred that those monomers be present in a minor amount and that they be used in conjunction with a larger amount of a moderately basic monomer. If a strongly basic monomer is used, it may be present up to about 5% by weight based on the weight of the monomer 10. total. More moderately basic polar monomers are preferred, alone or in. combination with other basic monomers. About 5 to 45% by weight of moderately basic monomers can be used, and especially from 15 to 30% by weight of basic monomer is preferred. Acid functional monomers include acrylic acid, b-carboxyethyl acrylate, methacrylic acid, itaconic acid, crotonic acid, fumaric acid and the like. Moderately basic monomers such as N, N-dimethyl acrylamide, N, N-dimethyl methacrylamide, N, N-diethyl acrylamide, N, N-diethyl methacrylamide, N-vinyl caprolactam, N-vinyl pyrrolidone, and the like are preferred. If an acidic functional monomer is used, it preferably comprises from 5 to 20% by weight of the copolymer. Functional monomers are typically copolymerized with the rest of the copolymer components at levels of about 5 to 50 parts by weight of the monomer composition, more preferably 10 to 40 parts per hundred by weight of the monomer composition. These functional monomers can also be used as crosslinking sites for the polymer. For example, acidic monomers can be reacted with crosslinking agents that react with the acid group, for example, epoxides or multifunctional isocyanates.

The acrylic copolymers useful in the heat-activatable adhesive of this invention contain from about 10 to 70 parts per hundred weight of monomer (% by weight), preferably from about 20 to 60% by weight, contained in the copolymer of at least a monomer which as a homopolymer has a high Tv. As used herein, "Tv aita" means that the corresponding homopolymer has a Tv of at least 50 ° C, preferably of at least 75 ° C, and more preferably of at least 100 ° C. Typically, the greater amount of high Tv monomer in the acrylate copolymers of the heat-activatable adhesive of this invention, the lower the adhesion and pre-adhesion of the adhesive and the higher the heat activation temperature, the lower the amount of those high Tv monomers, the higher pre-adhesion and lower activation temperature, the amounts of high Tv monomer and low Tv monomer are balanced to provide the desired properties. While the monomer can be polymerized with the rest of the monomers comprising the acrylic copolymer, any high Tv monomer, including styrene and the like, can be used. However, the high Tv monomer is typically an acrylate or methacrylate ester. Preferred high Tv monomers are monofunctional acrylate or methacrylate esters of cycloalkyl alcohols bonded by a bridge having at least 6 carbon atoms. and of aromatic alcohols. Both cycloaliquium and aromatic groups can be substituted, for example, by C? -6 alkyl, halogen, cyano, and the like. Especially preferred Tv-aita monomers include the 3,5-dimethyladamantium acrylate and methacrylate; acrylate and isobornyl methacrylate; 4-biphenylyl acrylate and methacrylate; phenyl acrylate and methacrylate; and 2-naphthyl acrylate and methacrylate. Mixtures of high Tv monomers can also be used. Preferably, the acrylic polymers useful as adhesives of the invention are crosslinked. This improves the adhesive cohesion resistance, making it easier to control the elastic modulus, activation temperature, and pre-adhesion adhesion. A cross-linking agent in the heat-activatable adhesive may preferably be present in an amount of about 0.05 to about 3% by weight, more preferably about 0.1 to 2% by weight, based on the weight of the monomers in the adhesive. Depending on the molecular weight and the equivalent weight of the acrylate of the components, up to about 20% by weight of crosslinking agent can be used. The crosslinking agent useful in the adhesives of the invention is typically an organic compound that reacts with the other monomers by virtue of having a plurality of ethylenically unsaturated groups, referred to herein as multifunctional acrylates. Alternatively, a crosslinking agent is a compound which can react directly with the polymeric backbone and result in crosslinking as, for example, in a zetiaiLpte or a cucad) taas co agent of pso? Ads or agirte reticulaite or efe cucacb , UV benzophenone. The adhesives of the present invention can be crosslinked before or after bonding the coating to a substrate. There are two main crosslinking mechanisms for the acrylic polymer adhesives of the invention: free radical copolymerization of multifunctional ethylenically unsaturated groups with the other monomers, and covalent or ionic crosslinking through the functional monomers, such as acrylic acid. Another method is the use of UV crosslinkers, such as copolymerizable benzophenones or photocrosslinkers added later, such as benzophenones and multifunctional triazines. High-energy radiation as well as an electron beam or gamma radiation is also useful. With the exception of the use of multifunctional vinyl unsaturated monomers, all crosslinking will take place after the coating of the polymers.

The crosslinking agents that are useful in the present invention can be selected from the group consisting of triazine compounds; acrylated urethanes such as diacrylated urethanes known under the trade designation EBECRYL, especially EBECRYL 230 (a polyurethane diacrylate available from Radcure Specialties, Inc., Norfolk VA); the crosslinking compounds by subtraction of hydrogen including the copolymerizable monoethylenically unsaturated aromatic cements, particularly the 4-acryloxybenzophenone (ABP), as described in U.S. Patent No. 4,737,559 (Kellen et al.), and multifunctional benzophenones subsequently added as described in US Pat. U.S. Patent No. 5,407,971 (Everaerts et al.), both of which are incorporated herein by reference; and multifunctional acrylates, such as 1,6-hexanediol diacrylate (HDDA). The crosslinking agents selected according to the polymerization method used. Preferred crosslinking agents for adhesives prepared via photopolymerization on the fabric are multifunctional acrylates such as 1,6-hexanediol diacrylate (HDDA) as well as those described in the Patent No. 4,379,201 (Heilmann et al.), Incorporated herein by reference, such as trimethylolpropane triacrylate, pentaerythritol tetraacrylate, 1,2-ethylene glycol diacrylate, and 1,12-dodecanediol diacrylate. Also useful as crosslinkers are the functional oligomers of acrylate and methacrylate, such as EBECRYL 230 which, in view of its high molecular weight, has a lower acrylic content than lower molecular weight diacrylates, such as diacrylate of 1, 6-hexan diol and the like, mentioned above. To compensate for this lower acrylate content, larger weight percentages of the oligomeric multifunctional acrylates in the adhesive composition can be used. Additional useful crosslinking agents include photoreticulators of the hydrogen sulfide type such as those based on benzophenones, acetophenones, anthraquinones and the like. These crosslinking agents can be copolymerizable or non-copolymerizable. Examples of copolymerizable hydrogen subtraction crosslinking agents include benzophenone; anthraquinones, and radiation-activatable crosslinking agents such as those described in U.S. Patent No. 5,407,971. Such agents have the general formula wherein W represents -O-, -N-, or -S-, X represents CH3- or femlo; Y represents a ketone, ester or amide functionality; Z represents a polyfunctional organic segment that does not contain the hydrophobic atoms that are capable of being rendered stronger than the hydrogen atoms of a polymer formed using the crosslinking agent; m represents an integer from 0 to 6; "a" represents 0 or 1; and n represents an integer of 2 or greater. Examples of copolymerizable hydrogen subtraction substances I crosslinking compounds include monoethylenically unsaturated aromatic ketones, particularly 4-acryloxybenzophenone (ABP), as described in US Patent No. 4, / 3 /, 539 (Kellen et al., incorporated herein by reference). Photoinitiators of the copolymerizable cleavage type, such as the functional disubstituted acrylamide acetyl aryl ketones, such as those described in PCT Application No. 94/10620, of the beneficiary hereof, filed on September 16, 1994, may also be used. which is incorporated here as a reference. In addition, combinations of multifunctional (meth) acrylates and crosslinkers of the type of subtraction of hydrogen or copolymerizable cleavage-type photoinitiators can be used. Low intensity UV light, such as "UV black light", is sufficient to induce crosslinking in most cases; however, when crosslinkers of the hydrogen subtraction type are used by themselves, high intensity UV exposure is necessary to achieve sufficient crosslinking at high linear speeds. Such exposure can be provided by means of a mercury lamp processor such as those available from PPG, Pittsburgh, PA, Aetek and others. Yet another method for crosslinking that does not necessarily require the addition of crosslinking agents is exposure to an electron beam. Other useful crosslinking agents include substituted triazines, such as those described in U.S. Patent Nos. 4,329,384 and 4,330,590 (both Vesley, both incorporated herein by reference), such as 2,4-bis (trichloromethyl) -6-p. -methoxystyrene-s-triazine and chromophoric halomethyl-s-triazines. The crosslinking agents useful for the preparation of the thermosettable adhesives polymerized in solution of the invention are those which are copolymerizable by free radicals and which effect the crosslinking through exposure to radiation, moisture or thermal flux after the polymerization. Such crosslinkers include the photoactive and photocrosslinking substituted triazines of the above-mentioned type of hydrogen subtraction. The free-radical, hydrolysable copolymerizable crosslinkers, such as the mono-, di-, and trialkoxy silane monoethylenically unsaturated compounds, including, but not limited to, 3-methacryloxypropyltrimethoxysilane (sold under the trade name of "Silane A-174" by Union Carbide Chemicals and Plastics Co.), vinyl dimethylethoxysilane, vinylmethyldiethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriphenoxysilane, and the like are also useful as crosslinking agents. Heat-activated copolymerizable crosslinking agents, including but not limited to N-methylol acrylamide and glycolic acid acrylate, can also be used to increase the shear strength of the pressure sensitive adhesive composition of the invention. Multifunctional aziridine crosslinking agents can also be used. Bisamide crosslinking agents are described more fully as compounds with the formula h} general (I): (D in which R; and R 'are the same or different and are independently selected from the group consisting of H and CnH2nt ?, where n is an integer ranging from 1 to about 5, and R' is a radical divalent selected from the group consisting of benzene (-C6H4-), substituted phenylene, and CmH7r1, where m is an integer ranging from 1 to about 10. An example of a useful multifunctional aziridine within general formula I is N , N'-bis-l, 2-propilenisophthalamide, which has the following structure (general formula II): (p) Other crosslinking agents can be used for the acid-containing polymers of the invention. They include epoxides, isocyanates and the like. The adhesives of the invention can be polymerized by conventional free radical polymerization methods, either thermally initiated or by radiation, including bulk polymerization processes. Preferred methods give high molecular weight polymers without the use of solvents, such as those obtained with suspension polymerization, in bulk. Particularly preferred is UV curing on the fabric, which gives the finished product in a single step.

Suitable thermal free radical initiators that can be used include but are not limited to azo compounds such as 2,2'-azobis (isobutyronitrile), hydroperoxides such as tert-butyl hydroperoxide, and peroxides such as benzoyl peroxide and cyclohexanone peroxide. Photoinitiators that are useful according to the invention include but are not limited to those selected from the group consisting of benzoin ethers such as benzoin methyl ether or benzoyl isopropyl ether, substituted benzoin ethers such as anisole methyl ether, substituted acetophenones. such as 2, 2-diethoxyacetophenone and 2,2-dimethoxy-2-phenyl acetophenone, alpha-substituted ketoles such as 2-methyl-2-hydroxy propiophenone, aromatic sulfonyl chlorides such as 2-naphthalene sulfonyl chloride and oximes photoactive For both thermally and radiation induced polymerizations, an initiator is present in an amount of about 0.01 to about 0.5 weight percent based on the total weight of the monomers of the thermoactivatable adhesive compositions herein. In a solution polymerization method, the high Tv and low Tv monomers and the functional monomer together with a suitable inert organic solvent and the free radical copolymerizable crosslinker are charged to a four-neck reaction vessel, which is equipped with an agitator, a thermometer, a condenser, an addition funnel and a thermal clock. After this monomeric mixture is charged into the reaction vessel, a concentrated thermal free radical initiator solution is added to the addition funnel. The entire reaction vessel and the addition funnel and their contents are then purged with nitrogen to create an inert atmosphere. Once purged, the solution inside the vessel is heated to about 55 ° C, the initiator is added, and the mixture is stirred during the course of the reaction. A conversion of 98 to 99 percent should be obtained in approximately 20 hours. Another polymerization method is a photopolymerization initiated by ultraviolet (UV) radiation in two steps of a monomer mixture at 100% solids. In the first step, the low viscosity monomers are mixed in the appropriate ratios and a photoinitiator is added to the mixture. The mixture is purged with nitrogen to remove the dissolved oxygen. A brief exposure to UV light results in a partially polymerized syrup with a moderate viscosity that can be easily coated. Add additional photoinitiator and crosslinker to the syrup. The syrup is then coated while oxygen is excluded to a desired thickness, usually about 0.5 to 10 mils (approximately 0.01 to 0.25 millimeters). During the coating process, the syrup is further exposed to a UV light bank to complete the polymerization and crosslinking of the adhesive. An alternative to the previous two-step method involves the use of an extruder. In this method, a bag is filled with plastic with monomers and initiators, with the addition of chain transfer agents to keep the molecular weight sufficiently low after polymerization, so that the polymer can be extruded. The filled bag is exposed to UV, which produces the polymerized composition inside the bag. The bag and the contents thereof are then fed to the extruder and the resulting molten composition is hot melt coated onto a coating, after which it is again exposed to UV or an electron beam to crosslink the adhesive, to give a composition comprising a thermoactivatable high molecular weight adhesive having a small percentage of such plastic polymeric material of the bag therein, typically 3 weight percent or less. Reactive extrusion, such as the continuous free radical polymerization method described in U.S. Patent Nos. 4,619,979 and 4,843,134 (both by Kotnour et al., Both incorporated herein by reference), can also be used to prepare the thermoactivatable adhesives of the invention. invention. Reactive extrusion is a solvent-free technology where polymerization is initiated by thermal means as opposed to UV radiation. The monomers together with the initiator are fed to an extruder. The temperature along the extruder varies to control the polymerization. Chain transfer agents are added to control molecular weight and prevent gel formation. The adhesive obtained at the end of the extruder is hot melt coated and cured by either UV light or electron beam to improve the cohesion resistance. The formulation of the heat-activatable adhesive of the invention is summarized below: : Can be seen as high as 20% by weight, The elastic modulus of the acrylic thermoactivatable adhesive (measured by the thermal, mechanical, dynamic analyzer, 628 rad / sec, compression mode) preferably ranges from approximately 5 x 106 to approximately 1 x 108 din / cm2 at 30 ° C. When the elastic modulus is less than 5 x 106 din / crn2 at 30 ° C the initial adhesion or "pre-adhesion", which will be described below, is very high, similar to that of a pressure sensitive adhesive, so that air will probably be trapped between the adhesive and the substrate during the application of the coating. When the elastic modulus exceeds 1 x 108 din / crn2, it becomes difficult to keep the sheet placed at the time of provisional joining even with the application of high pressure. Therefore, if the elastic modulus is between about 5 x 106 and about 1 x 108 din / cm2 at 30 ° C, the optimum properties are provided for the convenient provisional joint. When the elastic modulus has such a value, the heat-activatable adhesive can be placed as desired on a non-adherent substrate. When the heat-activatable adhesive is in the proper position, the application of pressure results in a weak temporary joint to maintain the position. If repositioning is desired, the adhesive can be easily lifted from the substrate and repositioned. The application of pressure again will provide a temporary bond, maintaining the position until the adhesive is activated by heat. A more preferred range of the elastic modulus at 30 ° C is from about 7.5 x 10fa to about 6.5 x 107 din / cm2, particularly preferred from about 1.0 x 107 to about 3.6 x 107 din / cm2. In the present invention, the elastic modulus of the acrylic thermoactivatable adhesive preferably ranges from about 5 x 105 to about 1 x 107 din / cm2 at 70 ° C. When the elastic modulus is less than about 5 x 105 din / cm2 at 70 ° C the cohesion resistance tends to be low, therefore, the adhesive tends to fail or be affected so severely that the coating can not be maintained on substrates severely cured, ie detachment is a problem. On the other hand, when the elastic modulus exceeds 1 x 107 din / cm2, it is difficult to carry out the final joining at a hot pressing temperature of at least about 70 ° C. If the temperature is higher than 70 ° C, the retroreflectivity of the structured coating tends to decrease due to the thermal distortion of the projections. When the elastic modulus is within the range, the final bond at the low hot press temperature becomes easier and a greater resistance to cohesion can be obtained. A more preferable range of elastic modulus at 70 ° C is from about 9.0 x 105 to about 8.0 x 106 din / cm2, particularly fluctuating, preferably from about 2.0 x 10b to about 6.0 x 106 din / cm2. The elastic modulus of the adhesives of the invention is a value measured at 30 ° C and 70 ° C by using the thermal, mechanical, dynamic analyzer Model RSA II available from Rheometrics Co. The conditions for measurement are as follows: the sample: cylindrical (external diameter = 3 to 3.5 mm, thickness = 6 to 8 mm) temperature range: -60 to 160 ° C frequency: 6.28 rad / sec measurement mode: compression mode. The elastic modulus of the heat-activatable adhesives of the invention is evaluated at 30 ° C due to the ability to hot press at 70 ° C as it also has a suitable pre-adhesion adhesion at room temperature (i.e., approximately 25 ° C), required for the adhesives useful in the present invention. The term "hot pressing temperature" represents a value of the surface temperature of the retroreflective sheet measured by the use of a thermocouple. Other additives can be added, such as an ultraviolet ("UV") absorber, an antioxidant, an agent for increasing the viscosity, adhesives, inorganic particles, etc., to the heat-activatable adhesives of the invention to a degree that does not interfere with the polymerization, severely reduce the desired transparency, substantially adversely affect the temperature of the transition or the elastic modulus of the adhesives. The adhesives of the invention are useful in the production of many different coating products or film types, particularly those where optical clarity is desired. One application of the adhesive is in a structured coating as shown in Figure 1. In Figure 1, the cube corner coating 7 comprises a coating or coating film 1 and a structured layer 2 having cube corner elements on the surface later of it. The typical coating film and preferably polymethylmethacrylate ("PBMA") containing a UV absorber to prevent degradation, while the corner, cubic retroreflective elements are preferably made of polycarbonate resins. It should be understood that the present invention can be used with any cubic corner optical design appropriate for the desired application. Illustrative examples of some cube-corner element designs that may be used in the invention are described in U.S. Patent Nos. 4,588,258 (Hoopman); 4,775,219 (Appeldorn); and 5,138,488 (Szczech). The structured coating 7 may also comprise a substantial, total and internally reflective film comprising a plurality of parallel prisms, such as described in U.S. Patent Nos. 4,805,984 (Cobb); 4,906,070 (Cobb); 5,056,892 (Cobb); 5,175,030 (Lu); or 5,183,597 (Lu). The elements formed precisely of the structured layer 2 and the sealing layer 3 define a plurality of concavities 10, filled with air or another fluid. "Substantial, total and internally reflective" pertains to the optical quality of the film, and means that the film has a Test T value of 5 percent or less, where Test T is as defined below. The optical quality of a retroreflective film can be evaluated with apparatuses including a laser (such as the SPECTRA-PHYSICS Model 117A Mark) with a spatial filter, a beam expander and a collimator. Two diaphragms or irises are placed at 18 and 38 cm from the laser, and an annular sample holder with a 6.35 cm diameter aperture is placed 84 cm from the laser. Directly behind the sample holder is an integration sphere (with an opening of 3 cm in diameter) and a LABSPHERE Radiometer Mark ML-400. Using the diaphragms or iris, the laser is focused through the aperture to obtain a clear circle of light approximately 3 mm in diameter on a black surface mounted on the sample holder. A source of intensity measurement of 100 percent is taken without the sample in place. The TIRF (Internally Reflecting Total Film) to be tested is then mounted on the sample holder with its flat surface facing the laser and its slots extending vertically. Unless otherwise reported, the T-Test values were measured at room temperature. The readings were then made at 12 to 15 different points on the TIRF within an area of 5 cm in diameter while ensuring that none of the light hits the frame of the sample holder. The readings are averaged and multiplied by 100 to give the percent of transmission which is the value of the T-test of the TIRF sample. The value of a T Test is a duplication fidelity criterion of the TIRF. The smaller percentages of the T-test value indicate better replication fidelity than larger percentages, and a T-Test value of 5 percent or less indicates that the film is substantial, total internally reflective. The coating film 1 preferably comprises an acrylic material having excellent durability, such as poly (methyl) methacrylate, a polyester, such as, for example, polyethylene terephthalate, polyamide, polycarbonate, polyvinyl chloride, poly (vinylidene chloride), cellulose acetate butyrate, cellulose acetate propionate, poly (ether sulfone), polyurethane, ionomer resins such as polyethylene / acrylic acid ionomers crosslinked with metal ions known under the trade designation of SURLYN, and similar, and preferably also comprises a UV absorber. From the viewpoint of aspects of mechanical strength and light reflectivity, layer 2 preferably has a refractive index of about 1.6, which is possible if the layer is made of a polycarbonate resin, an ionomeric resin as described above. , or an acrylic resin. In the case of cube-corner retro-reflective articles, the length of the base of the pyramidal cube corner element preferably ranges from about 0.1 to about 3.0 millimeters ("mm"), and more preferably ranges from about 0.2 to about 1.0 mm , to ensure good retroreflectivity and an appropriate wide angle. For flexible articles of the invention such as those to be worn on garments, a length of up to 0.625 mm is preferred.

The structured covering 7 can be made as an integral material, for example, by including a preformed sheet with a described arrangement of cube corner elements or by molding a fluid material in a mold; or it can be made as a laminated product, for example, by molding the elements against a preformed film as taught in US Pat. No. 3,684,348, or by laminating a preformed film on the front face of the individual molded elements. Polycarbonates and ionomers are the preferred integral sheet materials. The thickness of the structured coating 7 preferably ranges from about 50 to about 500 microns in terms of the height of the tip of the cube corner element or prism to the base of the base portion. If the thickness is less than 50 microns, the mechanical strength of the coating may not be sufficient and it is typically difficult to obtain a predetermined height for the pyramids or prisms, so that the retroreflectivity decreases. If the thickness exceeds 500 micrometers, on the other hand, the total thickness of the retroreflective sheet becomes so thin that handling becomes difficult and the amount of adhesive required increases. As stated above, the coating film should transmit light and is preferably substantially transparent. The polymer used in the coating film preferably comprises a polymer of moderate elastic modulus in order to be bent, rolled, flexed, shaped or stretched. The polymer used in the coating film also preferably has ductility, which can be expressed in terms of the Youngs modulus. The Youngs modulus can be from about 0.7 x 105 to 5.7 x 105 psi, and preferably from about 2.5 x 105 to 4.0 x 105 psi. The polymer should retain its physical integrity at the temperature at which it is applied to the cubic corner layer, and desirably have a Vicat softening temperature that is greater than about 50 ° C. Examples of polymers that can be used in the coating film include, but are not limited to: fluorinated polymers such as poly (chlorotrifluoroethylene), which is available, for example, under the trade designation KEL-F800 from 3M Co ., St. Paul, MN, poly (tetrafluoroethylene-co-hexafluoro-propylene), which is available, for example, under the trade designation EXAC FEP from Norton Performance, Brampton, MA, poly (tetrafluoroethylene-co-perfluoro ( alkyl) -vinyl ether), which is available, for example, under the trade designation of EXAC PEA from Norton Performance, and poly (vinylidene fluoride) or poly (vinylidene) fiuoride-co-hexafiuoropropyiene), which are available under the trade designation of KYNAR from Pennwalt Corporation, Philadelphia, PA; ionomeric ethylene copolymers such as poly (ethylene-co-methacrylic acid) with sodium or zinc ions, which is available under the trade designations SURLYN-8920 and SURLYN-9910 from E. I. duPont de Nemours, Wilmington, DE; low density polyethylenes such as low density polyethylene, linear low density polyethylene, and very low density polyethylene, plasticized vinyl halide polymers such as plasticized polyvinyl chloride; polyethylene copolymers including acid functional polymers such as poly (ethylene-co-acrylic acid) and poly (ethylene-co-methacrylic acid), poly (ethylene-co-maleic acid), and poly (ethylene-co-fumaric acid); acrylic functional polymers such as polymethacrylate, poly (ethylene-co-alkyl acrylates) wherein the alkyl group is methyl, ethyl, propyl, butyl, etc., or CH3 (CH2) n_ wherein n is 0-12, and poly (ethylene-co-vinylacetate); and aliphatic and aromatic polyurethanes derived from diisocyanates such as dicyclohexylmethane-4, 4'-diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, cyclohexyl diisocyanate, diphenylmethane diisocyanate, and combinations of these diisocyanates, polydiols such as polyethylene glycol glycol, polyethylene ether glycol, polyethylene glycol, polyethylene glycol; poly-i, 2-butylene oxide giicoi, and combinations of those polidioies, and chain extenders such as butanediol or hexanediol. Commercially available urethane polymers include PN-03 or 3429 from Morton International Inc., Seabrook, NH, or X-4107 from B. F. Goodrich Company, Cleveland, OH. The combinations of the above polymers can also be used in the coating film. Preferred polymers of the coating film include fluorinated polymers such as poly (vinylidene fluoride) (PVDF), functional acrylic polymers such as polymethylmethacrylate (PMMA), and combinations thereof. A particularly preferred group of polymers include mixtures of PVDF and PMMA containing about 60-95 by weight of PMMA and about 5-40 weight percent of PVDF. In such blends, PMMA contributes to the durability of the coating film while PVDF contributes to the chemical stability (eg, organic solvent) and flexibility of the coating film. Preferably, PMMA is not modified by impact. Such PMMA materials are also known as "linear" PMMA. Suitable sources of "linear" PMMA include Rohm &; Haas V044, V045, V052, V081 and the like. The PVDF is available from Soitex Poiymer Corp., Houston, IX under the trade designation of SOLEF or SOLVEY, of Pennwait Corporation under the trade designations KYNAR® 1010 and 1008; and from Elfatochem North America Inc., Philadelphia, PA under the trade designations TEDLAR 710 and 720. Those polymers are preferred for one or more of the following reasons: suitable mechanical properties; good adhesion to the cubic corner film; clarity; greater attachability by solvents; and environmental stability. The coating film may be a single layer or multiple layer film as desired. The interfacial adhesion between the coating film and the cube corner film can be improved by placing a small bonding layer between them. In addition, a surface treatment method, such as an electric discharge method (e.g., corona or plasma treatment) can be used to further improve the adhesion of the binding layer to the coating film or the coating layer. Union to the cubic corner layer. Typically, however, a tie layer or surface treatment methods are not required in the embodiments of the present invention. The polymeric materials used in the cube corner layer and the coating film may include additives such as acid scavengers and UV absorbers. These are particularly useful for preventing the degradation of polymeric material during processing and after exposure to environmental conditions (eg, heat and UV radiation). Examples of UV absorbers include benzotriazole derivatives such as those available under the trade designations TINUVIN 327, 328, 900, 1130, and TINUVIN-P from Ciba-Geigy Corporation, Ardsley, NY; benzophenone chemical derivatives such as those available under the trade designations UVINYL-M40, 408, and D-50 from BASF Corporation, Clifton, NH; and other related benzophenone derivatives such as those available under the trade designations SYNTASE 230, 800, 1200 from Neviiie-Synthese Organics. Colored colored film 3 is laminated on the structured surface of layer 2 and is bonded thereto with heat and / or radiation at a plurality of sites, thereby forming a plurality of sealed air cavities. When the cavities are described, "air" is used as an example only. Other fluids may be used depending on the atmosphere in which the articles of the invention are produced, and as long as the fluid used is significantly different in the refractive index of layer 2, with a difference in refractive index of about 0.5 or more preferred. The processes of US Pat. No. 4,025,159 (McGrath) can be used to effect the union of colored dyeing film 3 to the second surface of structured layer 2. Colored dyeing film 3 is preferably a plastic film comprising a resin plastic such as a polyester containing a suitable amount of one or more pigments such as titanium oxide, silica, red oxide, and the like, to impart the desired color. Illustrative examples of colors include white, gray, red, yellow, green, orange, blue, and brown. Dyes such as dyes and pigments can be used to impart the desired color to the sealant layer 3 as appropriate for the intended application. Those skilled in the art will be able to easily select suitable dyes and dye loads for the intended applications. White and gray are typically preferred for the present invention because the recognition capability of the retroreflective articles of the invention is greater when those colors are used. A particularly preferred resin for forming the colored sealing film layer is often the polyester resin because the pigment can be easily added to the resin. However, the bonding of the polyester films to the adhesive layers can be difficult.

H O In the present invention, an optional chemical priming layer or a corona treatment layer is preferably placed between the seaming film 3 and the heat-activatable adhesive layer 5. When starting a chemical priming layer and / or corona treatment, adhesion between layers between the film of the colored sealing layer 3 and the thermoactivatable adhesive layer 5 can be improved, making possible a greater adhesion of the articles of the invention to a substrate. Illustrative examples of suitable chemical primer coat types include urethanes, silicones, epoxy resins, vinyl acetate resins, ethylene imines, and the like. The selection of a priming layer or suitable treatment will depend in part on the characteristics of the sealing film 3, the adhesive layer 5 and the conditions under which the resulting article will be used. Those of the urethane and silicone type are particularly effective chemical primers for colored polyester sealing films. A suitable silicone type of primer layer has a continuous gelled network structure of inorganic particles, and is described in Japanese Unexamined Patent Publication (Kokai) No. 2-200476. This primer layer has a strong affinity for polyester resins and polyolefin resins. Illustrative examples of chemical primers for vinyl films and polyethylene terephthalate include the acrylic ester / acrylic acid copolymers described in U.S. Patent No. 3,578,622 (Brown). The acrylic adhesives of the invention generally adhere well to many surfaces. However, in some cases it may be useful to increase the adhesion to a substrate by increasing the mechanical interconnection of the adhesive with the substrate which can be done, for example, by abrading or etching the substrate or by priming with a material that significantly increases the surface area for the adhesive to adhere, such as the Msol primer discussed below. The acrylic adhesives used for this invention contain functional monomers, such as acrylic acid or N, N-dimethylacrylamide. These functional monomers can interact strongly with chemical primers by mechanisms such as hydrogen bonding, acid-base interaction or through the reaction of the adhesive / primer interface. The thickness of the chemical priming layer is suitably within the range of 10 to 3,000 nanometers ("nm"). If the thickness is less than 10 nm, the effect of the primer is minimal; if it exceeds 3,000 nm, on the other hand, a detachment between layers in the priming layer probably occurs. Corona treatment is a preferred physical priming method that can be applied in an appropriate manner to the surface of the colored sealing film layer on which the adhesive of the present invention will be coated. The corona treatment not only improves the adhesion between layers between the adhesive and the colored sealing film, but also provides advantages in the production process since it can be applied separately after the structured coating 7 and the colored sealing film layer 3 are sealed. A surface treatment 4 is preferred to obtain strong adhesion between the sealant film and the heat-activatable adhesive layer 5 as illustrated in Figure 1. In general, surface treatments can be described as chemical treatments, physical treatments and combinations of the same, so that the following illustrative surface treatments may be appropriate: 1) Aliphatic polyurethane primer coating (applied after corona treatment), an example of which is as follows (quantities in parts by weight): Table A 2) Coating of Msol primer after corona treatment. The Msol primer technology was based on Japanese Patent J02200476-A, of the Assignee, an example of which is presented in Table B (parts by weight amounts): Table B au 3) Corona treatment with nitrogen.

The corona treatment of the surface of the present invention can be carried out suitably in a nitrogen atmosphere because the duration of the adhesion improvement between layers is high. The useful energy density of the corona treatment with nitrogen ranges from about 15 to 500 watts / meter2 / minutes, preferably from about 80 to 250 watts / meter2 / minute. The energy density can be calculated from the equation Energy Density (watts / meter2 / minute) = Net Power (W) Electrode Width (m) x Linear velocity (cm / mm) where the electrode width is 0.035 m and the net energy and linear velocity can be changed to obtain the desired energy density. Corona treatment of films is a well-known technique, and is generally described in Cramm, R. H., and Bibee, D.V., The Theory and Practice of Corona Treatment for Improving Adhesion, TAPPI, Vol. 65, No. 8, pp. 75-78 (August 1982). The heat-activatable adhesive of the invention can be used in the manufacture of a variety of articles Ol different, some of which are illustrated in Figures 2 to 5. Figure 2 describes, in a perspective view, a signaling article made using the heat-activatable adhesive of the invention. The article, having the desired thickness 11, width 12 and flat length 13, also has a rounded edge 15. The curvature of the rounded edge is indicated by the radius R. The retroreflective facing articles 14 adhere to the article by means of a heat-activatable adhesive layer of the invention and remain in place without "peeling" at the edge of retroreflective coating articles 16. Figure 3 shows a retroreflective coating for cross-sectional heat-activated transit control similar to the retroreflective coatings described at the beginning . In this article the cover film 21 is attached to the prismatic layer 22. The prismatic layer 22 has a sealing film 23 attached to its structured surface with a plurality of sealed air cavities formed between the two layers as described in detail for the Figure 1 above. The sealing film layer is attached to a primer layer 24, which may be, for example, the primer layer Msol described in Table B. A primer coating of the polyurethane type as described in Table A, a treatment of crown, and so on. The heat-activatable adhesive layer 25 is placed on the primer layer 24 and a protective release liner 26 is placed on the heat-activatable adhesive layer to protect the adhesive and will be removed prior to hot lamination. The retroreflective coatings of the invention may optionally also comprise an additional film layer 27 which has protective properties. Examples of suitable films are those films having anti-graffiti, anti-gray, anti-humidity, chemical resistant, heat and / or impact films. If such a film is used it should be attached to the coating film 21 with a layer of heat-activatable adhesive of the invention 25. In addition to the use in the preparation of retroreflective coatings, the heat-activatable adhesive of the invention can be used in the preparation of graphic films or decorative as seen in Figure 4. For example, the heat-activatable adhesive can be used to adhere a coating resistant to stains or heat on a decorative film product, allowing it to be used in heavy-duty applications, such as for roofing of tables, lobbies for bars, kitchen lobbies, and so on. An illustrative graphic film is described in cross section in Figure 4. The graphic film of Figure 4 has a hard coating 31 which is a heat resistant film., stains and / or chemical products, which protects the rest of the coating. This hard coating layer can be made of any suitable polymeric material, but is preferably a UV curable acrylic resin. This hard coating 31 is followed by a transparent film layer 32, for example, a polyester film, which is used to smooth the graphic film and obtain excellent hardness together with the hard coating. This transparent film is useful to prevent migration of the plasticizer, so that excellent stain resistance can be obtained. This film is joined by means of a heat-activatable adhesive layer 33 containing a functional monomer such as NNDMA to a clear PVC layer 36. A printing layer or other decorative layer 35 can be adhered to the clear PVC layer followed by a layer Basic colored PVC 36. A layer of pressure sensitive adhesive 37 is placed on the surface of the base colored PVC with the protective release liner 38 on the surface of the pressure sensitive adhesive. In an additional graphical application as shown in Figure 5, a layer of clear PVC 41, optionally with D a pattern etched on its surface, has a decorative printing layer 42 attached to its back or smooth surface. A layer 43 of the heat-activatable adhesive of the invention is placed on the surface of the printed layer. Although optical charity is not critical in this particular application, a low thermal activation temperature is desirable in view of the thermal sensitivity of the PVC film. A layer of aluminum or other metal sheet 44 is placed on the surface of the heat-activatable adhesive. On this surface is a layer of pressure sensitive adhesive 45 for bonding the article to the desired substrate. On the surface of the pressure-sensitive adhesive is a protective release liner 46 for protecting the surface of the adhesive. When the microduplicated film with optical properties such as those described in U.S. Patent No. 4,775,219 (Appledorn) can be laminated to typical glass surfaces, the adhesive used in the lamination to be optically clear, so as to leave the microduplicated films with the optical quality and should be thermoactivable at a moderate temperature to prevent distortion of the films and their resulting optical changes. For example, the heat-activatable adhesive of the invention can be used to laminate or adhere a film, such as a microduplicated film, directly to a glass surface such as a computer screen or other monitor. In other applications, such as automotive or other window type applications, the film will typically be laminated in a "sandwich" configuration between two glass panels. Clearly, the heat-activatable adhesive of the invention is useful in a wide range of coatings or coating products having a multitude of end-uses ranging from light control or optical properties to anti-graffiti films for retroreflective articles. The figures described above are not to scale and are not intended to limit but rather illustrate the invention.

EXAMPLES The invention will be better explained by the following illustrative examples which are intended not to be limiting. Unless otherwise indicated, all quantities are expressed in parts by weight. In the following examples, the acrylate monomers and functional monomers were mixed at the respective weight percentages indicated in each example, with 0.1 weight percent of photoinitiator known under the trade designation ESACURE KB-1, 2, 2-dimethoxy-2 -? phenylacetophenone available from Sartomer Co. The resulting solutions were deaerated for 10 minutes with nitrogen gas, and then polymerized at an 8-12 percent conversion using low intensity UV lamps under nitrogen gas. The polymerization could be stopped by exposure to oxygen. Various types of crosslinkers and 0.2 additional percent of photoinitiator were added to the solution in the form of syrup and then mixed thoroughly. The crosslinkers used in the examples were the 1,6-hexanediol diacrylate (HDDA), triazine XL-353 available from 3M, which is 2,4-bis (trichloromethyl) -6- (3,4-dimethoxy-phenyl) ) -s-triazine, 4-acryloxybenzophenone (ABP), and urethane diacrylate (EBECRYL 230 available from Radcure Specialties). The following two curing methods were employed.

I. Open face curing The syrup-shaped solutions containing the XL-353 crosslinker were coated on a siliconized paper coating to 4 mils (0.01 cm) by means of a mounting bar and the cloth was irradiated with a low intensity UV lamp (Black UV light from Sylvania, which emits between 300 and 400 nm with a peak around 350nm and / or an intensity around 2 mW cirf **) under nitrogen gas. The total dose of UV light was 420.7 millijoules / square centimeter ("mj / cm2").

II. Double Coating Curing The syrup solutions containing HDDA, ABP, and urethane diacrylate were coated onto a siliconized paper liner at 4 mils (0.01 cm) by means of a mounting bar and the siliconized polyester film was laminated to the fabric. The sandwich fabric was made through a low intensity UV lamp which dosed a total of 444.2 mj / cm2. In the case of the syrup containing ABP, the cloth was irradiated with a high intensity UV lamp after irradiation of low intensity UV light. The total dose of high intensity UV light was 429.0 mj / cm2. The total dose was measured by a UVIMAP radiometer (Electronic Instrumentation and Technology, Inc.). The heat-activatable adhesives were also obtained by solvent polymerization, however, the adhesives may exhibit slightly different properties than those cured by UV polymerization. For example, the retention energy on highly curved surfaces can be more oo low and the samples may be more suitable for applications to flatter surfaces.

Example i 60 weight percent isooctyl acrylate, 10 weight percent acrylic acid, and 30 weight percent isobornyl acrylate were mixed with 0.1 weight percent photoinitiator (Sartomer, Co., ESCACURE KB-1) . The resulting solution was deaerated for 10 minutes with nitrogen gas, and then polymerized to a conversion of 8.7 percent using a low intensity UV lamp under nitrogen gas. The polymerization was stopped by exposing the solution to the air. 0.2 parts by weight, based on the total weight of the monomers, of triazine (XL-353) and 0.2 weight percent of additional photoinitiator were added to 100 parts by weight of the solution in the form of syrup and mixed thoroughly. The solution in the form of syrup was coated on a siliconized paper liner at 4 mils (0.01 cm) by means of a mounting bar and the fabric was irradiated with a low intensity UV lamp under nitrogen gas. The total dose of UV light was 420.7 mj / cm¿. 33 The elastic modulus at 30 ° C and 70 ° C, transparency, glass transition temperature, preadhesion, and post-adhesion are shown in Table 1. The test methods for those measurements were as follows: - Elastic modulus: described above. Transparency. The cured thermoactivable adhesive, which was coated to 4 mils with a mounting bar, was laminated with Toyobo 50 mm A4100 polyester film on both sides of the adhesive and the sample was measured by means of an integration sphere photometer according to section 5.5 in JIS K7105. Vitrea transition temperature: described above. - Pre-adhesion: The heat-activatable adhesive was coated on the siliconized paper coating at 4 mils (0.01 cm) by means of a mounting bar and cured, and then a 50 mm aluminum sheet was laminated to the adhesive at 70 ° C by means of a thermal laminator. The sample was cut to 1 inch (2.54 cm) in width and the test piece was allowed to equilibrate at 20 ± 2 ° C and 65 ± 5 percent in relation to moisture (as per the JIS Z8703 test standard) for 24 hours. hours. A 3 mm thick polycarbonate substrate was cleaned with isopropyl alcohol, and then the o? Test piece was laminated to the substrate by means of an automatic laminator with a laminating speed of 5 mm / second as described in JIS Z0237. Immediately after rolling, the peel force was measured by means of a tensile tester known under the trade designation INSTRON with a peel angle of 90 ° and a peel rate of 300 mm / minute. The pre-adhesion was defined as the average detachment force three measurements. - Postadhesion. The same method described above was used to measure post-adhesion, except for the following changes: the use of aluminum sheet 80 mm and 1 mm aluminum panel as a test substrate, and HLVA for the final union before the measurement. The heat-applied cubic corner retro-reflective cladding was made by the same method described above except the use of cubic corner retro-reflective cladding primed with Msol in place of the siliconized paper coating, which is directly coated on the cladding. The properties of that coating are shown in Table 2 below. The measurement methods are described below: - Whiteness: 01 Whiteness was measured in terms of Cap Y (D65 / 2 °) by the use of a S 80 Colorimeter (Nipping Denshoku Kogyoh). A high Cap Y value means that the whiteness is high. The color of the white coating could be set in the following color box: l (x = 0.305, y = 0.305), 2 (x = 0.355, y = 0.355), 3 (x = 0.355, y = 0.375), 4 (x = 0.285, y = 0.325). See ASTM Standards on Color and Appearance Measurements, Standard E308. Operation of the provisional joint: The ease of placing the retroreflector cubic corner coating in this mode was evaluated at a predetermined bonding site (an aluminum substrate for marking roads). Where the placement was easily achieved and a temporary or temporary joint was formed after the application of pressure, it was evaluated as "Excel" for excellent, where the reflective coating does not adhere but is used along the aluminum surface with low friction it was evaluated as "Slip" for the undesirable sliding of the coating; and wherein the coating aggressively adhered, so that it could not be easily peeled off manually was evaluated as "Adherent" because the coating placement was impossible due to excessively high adhesion. 0 Application temperature of HLVA (hot pressing temperature) The application temperature of HLVA when the cubic corner retro-reflective cladding was bonded to the road marking aluminum substrate was measured by placing a thermocouple in contact with the surface of the cladding. Loss of retroreflectivity after the application of HLVA: The percentage of retroreflectivity loss was measured after the cubic corner coating was bonded to the aluminum substrate for road marking as described above was evaluated using retroreflectivity before bonding like 100 percent. The retroreflectivity was measured at the angular conditions of an observation angle of 0.2 ° and an input angle of -4 °. Bonding test: The 90 ° adhesion of the cubic corner retro-reflective coating was carried out after HLVA application based on JIS Z0237. The case where the release force was greater than 1.5 kilograms force / inch ("kgf / in") or the coating could not be peeled off without damaging the coating was evaluated as "Excel" for excellent, and the case where the DJ Detachment occurred between the adhesive layer and the coating was evaluated as "Deslam" for delamination. Rounded Edge Test: Test panels with radii ranging from 3 to 10 mm were made as shown in Figure 2. The panel size was 15 x 70 x 110 mm. Two 1-inch (2.54 cm) wide sample pieces of a cubic-corner retro-reflective coating applied by heat by HLVA to the panels after being cleaned with a 2% aqueous solution of non-ionic emulsifier were applied (polyethylene glycol alkylphenyl ether). The application temperature of HLVA was chosen as shown in Tables 2 and 4. After each test piece (substrate with the samples attached to it) was cooled, the edges of the projected test samples were cut. In this way, the test samples were attached to substrates having radii of curvature of 3 to 10 mm, and aging-proof to the environment was carried out in 14 cycles under the conditions listed below to observe the failure to detach of the retroreflective sheet of the curved surface. As a result, the minimum value of the radius of curvature of each test piece substrate was used, in which the removal by detachment of the retroreflective sheet was not observed OR for two test samples, as a test result. Radio = 3, 4, 5, 6, 7, 8, 9 and 10 mm.

Conditions of 1 cycle of aging test to the environment * 1. -30 ° C, 0 percent RH (relative humidity) (2 hours) ~ (1 hour) - 2. 23 ° C, 65 percent RH (0.5 hours) - (0.5 hours) -3. 40 ° C, 95 percent RH (2 hours) ~ (0.5 hours) - 4. 23 ° C, 65 percent RH (0.5 hours) ~ (0.5h) ~ 5. -30 ° C, 0 percent of HR (1.5 hours) - (lh) ~ 6. 23 ° C, 65 percent RH (0.5 hours) ~ (1 hour) - 7. 80 ° C, 50 percent RH (1 hour) ~ (lh -8. 23 ° C, 65 percent RH (0.5 hours) * The conditions of the cycle were originally used in the automotive industry to provide a correlation of outdoor weathering. The first time listed in each step is the period of time in which the sample was allowed to remain at the indicated conditions. The time between two different conditions, for example ~ (1 hour) -, is an interval to change to reach the next condition.

DO 2 The same procedure as in Example 1 was carried out except that 0.4 parts by weight of triazine crosslinker (XL-353) was added. The discoveries are shown in Tables 1 and 2. 3 The same procedure was carried out as in Example 1 except that 0.6 parts by weight of triazine crosslinker (XL-353) was added. The discoveries are shown in Tables 1 and 2.

Example 4 The same procedure as in Example 1 was carried out except that 0.2 parts by weight of ABP crosslinker was added and the double coating process was used. This time the coating was primed with NEOREZ.

Example 5 The same procedure was carried out as in Example 4 except that 0.2 additional parts by weight of DD were added.

ABP crosslinker in place. The discoveries are shown in Tables 1 and 2.

Example 6 The same procedure as in Example 4 was carried out except that an additional 0.4 parts by weight of ABP crosslinker was added. The discoveries are shown in Tables 1 and 2.

Example 7 The same procedure as in Example 4 was carried out except that n-butyl acrylate was used instead of isooctyl acrylate and 0.1 part by weight of HDDA crosslinker was added. The coating was also primed with M-sol solution. The discoveries are shown in Tables 1 and 2.

Example 8 The same procedure was carried out as in Example 7 except that 4.4 parts by weight of urethane diacrylate crosslinker (Ebecryl 230) was added and the coating was D '. printed using nitrogen corona. The discoveries are shown in Tables 1 and 2.

Example 9 The same procedure as in Example 8 was carried out except that 8.8 parts by weight of urethane diacrylate crosslinker (EBECRYL 230) was added. The discoveries are shown in Tables 1 and 2.

Example 10 The same procedure as in Example 8 was carried out except that 13.2 parts by weight of urethane diacrylate crosslinker (EBECRYL 230) was added. The discoveries are shown in Tables 1 and 2. 11 The same procedure was carried out as in Example 8 except that 81 weight percent isooctyl acrylate and 19 weight percent acrylic acid were used and 0.2 weight part HDDA crosslinker was added. The discoveries are shown in Tables 1 and 2.

DO Example 12 120 g of methyl methacrylate, 40 g of N, N-dimethyl acrylamide and 40 g of isooctyl acrylate were charged to a reaction vessel containing 300 g of ethyl acetate and 0.6 g of VAZO "* 64 (DuPont Chemical) The vessel was purged with nitrogen, sealed and stirred for 24 hours in a water bath at 55 degrees C. The resulting polymer could be diluted with ethyl acetate to 30% solids and coated to give a non-stick film, Optically clear This adhesive film was positionable at 70 ° C and can be heat-laminated around 110 ° C between two pieces of plasticized vinyl (PanaflexMK available from 3M Company) to give a strong bond After aging (9 days to 65) ° C), the two pieces of PVC can no longer be separated without destruction of the vinyl.

Example 13 The same fillers and reaction conditions as in Example 12 were used, but 0.2 g of carbon tetrabromide was also charged to reduce the molecular weight of the polymer. The polymer can be coated at 40% solids to give a clear, non-stick film, which remains placeable at around 70 ° C, will be heat-laminated even at PVC around 110 ° C. Again, a very good union was obtained.

Example 14 The same charges as in Example 12 were used, except that the methyl methacrylate was replaced with ethyl methacrylate. The solution coating gave a clear, non-stick film, which remains placeable up to about 50 ° C, is still heat-laminable to plasticized vinyl around 90 ° C and gives a strong bond.

Example 15 The same charges as in Example 13 were used, except that the methyl methacrylate was replaced with ethyl methacrylate. The solution coating gave a clear film with very light adhesion but can be placed up to around 50 ° C. Heat lamination to plasticized vinyl at 90 ° C gives a strong bond. The above samples show that optically clear adhesives with good properties l? termoactivabies for PVC application can be obtained from a solution. To remove the solvents from the process, the monomers may be polymerized in suspension but an additional step may be necessary to convert the polymer beads into a thin coating. Bulk polymerization directly on the fabric is highly preferred because the article coated with the adhesive film or adhesive resting freely is obtained in one step. Due to the high volatility and flammability of some monomers, the selection of monomers for polymerization on the fabric is more limited. For example, monomers such as methyl acrylate or ethyl acrylate are highly flammable and odorous to be handled safely, and non-flammable monomers such as isobornyl acrylate will have to be replaced as a monomer that gives a higher Tv. The following examples demonstrate the use in UV initiated dual coating to cure the adhesives useful for PVC applications.

Example 16 A mixture of 30 g of isobornyl acrylate, 30 g of N, N-dimethyl acrylamide, 40 g of isooctyl acrylate and 0.3 g of EsacureMK KB-1 was purged with nitrogen and exposed to / 1 low intensity UV light ("black light" from Syivania UV) to make a cohesive syrup. Once the coating viscosity was obtained, the reaction was stopped by turning off the UV light and exposing the syrup to oxygen. The syrup was then fully polymerized as exposed under the curing of the double coating discussed above.

Example 17 This sample was made in a similar way the Example 16, but 20 g of isobornyl acrylate, 30 g of N, N-dimethyl acrylamide and 50 g of isooctyl acrylate were used. At room temperature, both UV cured samples can be easily placed on a Panaflex ™ substrate. The laminación by heat to 80 ° C gives a good union to the PVC without catching bubbles of gas. The adhesive does not discolor and is optically clear. As expected, high levels of isobornyl acrylate will increase the activation temperature but will also lead to embrittlement of the adhesive.

Comparative Example 17.2 grams ("g") of synthetic butadiene / acrylonitrile rubber were vulcanized (Nippon Zeon Co., Nipol I? N009) and 0.5 zinc oxide (New Jersey Zinc Co. Inc., Protox 166) with a rubber mill. 60.4 g of MEK (methylethyl ketone) and 10.4 g of phenolic resin (Reichhold Inc., Varcum 861) were added to the granulated synthetic rubber and the mixture was then stirred thoroughly. The solution was coated on a laminated polyethylene release liner and dried in an oven at about 25 ° C for 5 minutes, 65 ° C for 5 minutes, and 93 ° C for 3 minutes to give a heat-activatable adhesive having a weight of 90.4 g / m2 coating. The findings are shown in Table 3. The adhesive was laminated to a prismatic retroreflective coating primed with Msol at 75 ° C by the use of a thermal laminator. The properties are shown in Table 4.

Comparative Example 0.23 g of 5 weight percent bisamide crosslinker in toluene and 15 g of methyl ethyl ketone were added to 100 g of an isooctyl acrylate: acrylic acid copolymer 93: 7, and the solution was mixed thoroughly. The solution was coated on a siliconized paper coating and dried at room temperature (approximately 75 ° C) for 5 minutes, 65 ° C for 4 / J minutes, and 95 ° C for 3 minutes. As a result, a pressure sensitive adhesive (133.9 g / m2) was obtained and the findings are shown in Table 3. The adhesive was laminated to a prismatic retroreflective coating primed at room temperature by means of a laminator. The properties are shown in Table 4.

Comparative Example The same procedure as in Example 1 was carried out, except that 90 weight percent isooctyl acrylate and 10 weight percent acrylic acid and the addition of 0.18 weight part triazine crosslinker (XL-353) were used. . The discoveries are shown in Tables 3 and 4.

Table 1 Thermoactivable Adhesives of Examples 1-11 0 ß Table 2 I D Table 2 Heat Applicable Binocular Retruereflective Coatings of Examples 1-11 U O? O / D Table 3 Comparative Examples 1-3 ? Table 4 or Comparative Examples 1-3 or The different modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following:

Claims (11)

1. A thermoactivatable adhesive composition, characterized in that it comprises an acrylic copolymer, the copolymer comprises: (a) about 10 to 85% by weight based on the weight of the monomer of a monomer consisting of an acrylate or methacrylate ester of an alkyl alcohol not tertiary having a Tv of about 0 ° C or less; (b) about 10 to 70% by weight based on the weight of the monomer of a monomer consisting of an acrylate or methacrylate ester of an alcohol having a Tv of at least about 50 ° C; and (c) about 5 to 50% by weight based on the weight of the monomer of a functional monomer.

2. The adhesive composition according to claim 1, characterized in that it is substantially transparent after application and after aging.

3. The adhesive composition according to claims 1-2, characterized in that the monomer (a) comprises an acrylate or methacrylate ester of a non-tertiary alkyl alcohol, wherein the alkyl portion contains from 4 to 12 carbon atoms and wherein the monomer (b) comprises an acrylate or methacrylate ester of a cycloalkyl alcohol linked by a bridge having at least 6 carbon atoms or an aromatic alcohol.

4. The adhesive composition according to claims 1-3, characterized in that the monomer (a) is selected from the group consisting of n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, 2-methyl butyl acrylate, acrylate of 2-ethylhexyl, 2-ethylhexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, isooctyl acrylate, isooctyl methacrylate, isononyl acrylate, isodecyl acrylate, and mixtures thereof.

5. The adhesive composition according to claims 1-4, characterized in that the monomer (a) is selected from the group consisting of n-butyl acrylate, 2-methyl butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate and mixtures thereof.

6. The adhesive composition according to claims 1-5, characterized in that the functional monomer contains a polar functional group selected from the group consisting of carboxylic acid, sulfonic acid, phosphoric acid, hydroxy, lactam, lactone, substituted amide, substituted amine and carbamate .

7. The adhesive composition according to claims 1-6, characterized in that the functional monomer is selected from the group consisting of acrylic acid, b-carboxyethyl acrylate, methacrylic acid, crotonic acid, fumaric acid, N, N-dimethyl acrylamide, N , N-dimethyl methacrylamide, N, N-diethyl acrylamide, N, N-diethyl methacrylamide, N-vinyl caprolactam and N-vinyl pyrrolidone.

8. The adhesive composition according to claims 1-7, characterized in that the monomer (b) is selected from the group consisting of 3,5-dimethyl adamantyl acrylate, 3,5-adamantyl methacrylate; isobornyl acrylate, isobornyl methacrylate; 4-biphenylyl acrylate; 4-biphenylyl methacrylate; 2-naphthyl acrylate; 2-naphthyl methacrylate; and mixtures thereof.

9. A retroreflective article, characterized in that it comprises a retroreflective coating having a substantially planar surface and a structured surface, the structured surface is comprised of a plurality of accurately formed projections, a colored layer deposited on the structured surface, and adhered thereto in a plurality of discrete locations, and the thermoactivatable adhesive layer according to any of claims 1 to 8 placed on the colored layer.

10. A coating article, characterized in that it comprises: (a) a hard coating; (b) a polyester layer; (c) a thermoactivatable adhesive layer according to any of claims 1 to 9; (d) a clear polymer layer; (e) a decorative layer; and (f) a layer of pressure sensitive adhesive.

11. A coating article, characterized in that it comprises: (a) a embossed or textured layer; (b) an optional printed layer; (c) a thermoactivatable adhesive layer according to any of claims 1 to 9; (d) a sheet metal layer; and (e) a layer of pressure sensitive adhesive.