MXPA00002520A - Release liner for pressure sensitive adhesives - Google Patents

Abstract

A release liner for use with a pressure sensitive adhesive. The release liner includes a film of a thermoplastic elastomeric olefin.

Description

RELEASE COATINGS FOR PRESSURE SENSITIVE ADHESIVES FIELD OF THE INVENTION This invention is concerned with a release liner for pressure sensitive adhesive articles.

BACKGROUND OF THE INVENTION Currently, many pressure sensitive adhesive tapes and other articles coated with pressure sensitive adhesive have a release coating applied to the adhesive during or after manufacture. For example, the release liner can serve as a carrier for a pressure sensitive adhesive transfer tape or a tape coated on both sides, both of which are sticky or tacky on both sides of the tape. The adhesive tape in a release liner is commonly fed into a roll wound in convolution and then unrolled and laminated to an article or substrate. The release liner is commonly left in place as the article is converted, packaged and packaged to the end users and in many instances is left in place until the article is glued to and adhered to another substrate with the adhesive sensitive to the pressure. Are used REF .: 32998 release liners for one or more of a variety of purposes including, for example, preventing contamination of the adhesive layer, facilitating handling of the "coated with adhesive" article (eg, by providing support thereto as well) how to cover the adhesive) to identify the articles to which they are applied, etc. The type of adhesive is commonly made to correspond to the type of release coating, for example, the release coatings of the state of the art for pressure sensitive tapes. , acrylic, polyethylene or polypropylene films, these films have been successfully used for acrylic pressure sensitive adhesives for many years because they do not require a separate coating (eg, silicone) to provide a release surface. Silicone-coated polyester release liners are also well known in The technique: Conventional olefin or polyester based release coatings that work well at ambient temperatures, however, are often not suitable for use in manufacturing processes involving heating and cooling a substrate after application of an adhesive tape but before removal of the release coating. For example, During the painting process, the painted thermoplastic automotive parts are commonly exposed to temperatures of around 120 ° C (250 ° F) or higher for extended periods of time to cure the paint and then cooled. It is often desirable to apply an adhesive tape with a release coating to an unpainted substrate, to paint the substrate and to cure the paint at high temperatures, then to remove the release coating after cooling. However, the coatings of The release of polyethylene can not withstand the high temperatures used in paint curing ovens and can melt, expand or contract or bend during procedures involving heating and cooling. The polyester coatings coated with silicone can withstand high temperatures, but they are also not suitable for applications involving thermal cycling because they do not expand and contract at the same rate as thermoplastic polyolefin substrates when heated and cooled and polyester coatings tend to pull the ends of the adhesive tape after heating or ripple in the subsequent cooling. What is needed in the industry is a release liner for adhesives sensitive to pressure, particularly for acrylic foam tapes that ^ x¿ £ ± - .. ^ -so afaM ^ ^? iiMftrfr'iiiMg r¡? r? ri is appropriate for use in manufacturing applications involving heating and cooling of a substrate.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a release liner for pressure sensitive adhesive articles such as single sided tapes or double sided tapes, films, labels and the like. The release coating of the present invention comprises a thermoplastic elastomeric olefin (TEO). The TEO imparts thermal stability to the coating, such that it is not likely to decompose significantly or melt when exposed to elevated temperatures during the manufacture and processing of a typical substrate to which it is applied. The use of TEO in the release coating also decreases the likelihood of the coating contracting significantly from the adhesive after heating or significantly rippling on cooling. Thus, the release coating of the present invention is especially suitable for, although not limited to, use in manufacturing processes carried out at elevated temperatures, particularly those involving heating at temperatures such as exposure to temperatures of about 90 ° C. at about 150 ° C for periods up to half an hour and one hour or more, followed by cooling to room temperature (this is about 20 ° C to about 25 ° C). Preferably, the release coating is a film, ie a sheet material, having at least one release surface comprising a release material such as a silicone, polyethylene, fluorocarbon, polypropylene or a combination thereof (eg example a mixture). The release surface may be provided as an integral part of the release coating or alternatively in the form of a separate release or coating layer. The release surface imparts the desired surface adhesion and release characteristics to the release coating in view of the adhesive which the coating is to be applied. It also works to create a coherent surface to which the pressure sensitive adhesive can be laminated. A preferred embodiment of the release coating comprises: (i) a center or core of TEO and (ii) a release layer or coating comprising a release material comprising a polyethylene, polypropylene, fluorocarbon, silicone or a combination thereof (e.g. a mixture). The release coating or coating provides the release surface that contacts the adhesive. The center or core of TEO may be composed exclusively of one TEO or may be a combination of TEO and one or more materials such as polyethylene. In another preferred embodiment, the release coating comprises a mixture, preferably a combination of TEO and at least one other material, preferably a release material such as polyethylene or silicone, in proportions to provide the surface of As an integral part of the release liner, a separate coating or release layer is not included. The present release coating is preferably resistant to tearing. Exhibits from Preference is given to a low release value of acrylate based adhesives, as described hereinafter and has a high resistance in the transverse direction of the tape. A notch or tear in the release coating of the present invention is commonly not will propagate as a tear in a polyethylene or polypropylene liner. When present, the release coating further reduces the stresses in the release liner during the removal of the adhesive.

It is also provided by the invention, a method for manufacturing a release liner for use with an applied adhesive. to a substrate during a heating and cooling cycle. The method involves adapting a release coating of a material that exhibits thermal expansion and contraction properties similar to those observed for the proposed substrate. For example, the coefficients of thermal expansion and contraction of the substrate can be measured and an extrudable material exhibiting similar thermal coefficients can be selected or manufactured. A film comprising the selected material is extruded and at least one release surface is provided on the film for release of the adhesive film. The extruded film is thermally stable under the conditions of manufacture or processing (for example, a thermal cycle involving exposure to an elevated temperature for a defined period of time) to which the proposed substrate (after application of the coated adhesive) release) will be submitted. Preferably the proposed substrate comprises a TEO and the release coating is also formulated from a TEO, preferably a degree of extrusion of the same TEO. In a particularly preferred embodiment of the method of ? fKS-l? ' In the invention, the proposed substrate is an automotive body part comprising TEO. The present invention further provides a method for using a release coating during the heating and cooling of a proposed substrate. A release coating is adhered to a pressure sensitive adhesive, then applied to a substrate. The substrate is exposed to elevated temperatures for a period of time, then restored to room temperature. He The release liner does not undulate or significantly bend or shrink substantially from the pressure sensitive adhesive during heating or cooling processes and preferably remains coextensive with the pressure sensitive adhesive after being restored. at room temperature.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Preferred release coatings of the invention take the form of a film (ie, a sheet material) comprising a thermoplastic elastomeric olefin (TEO). As described herein, the terms coating, release coating, release film and release sheet are interchangeable. Thermoplastic elastomeric olefins (TEO), also referred to in the art as polyolefins ^^^^^^^^^^^^^ g ^^^^^^^^^ H thermoplastic (TPO) are a class of materials that are thermoplastic and elastic by nature. The TEO is commonly a combination of a rubberized or rubberized material, such as for example an ethylene-propylene rubber (or rubber) (such as ethylene-propylene monomer [EPM] or ethylene-propylene-diene monomer [EPDM]) , a nitrile rubber or a styrene butadiene rubber, with a thermoplastic (such as polypropylene, polyethylene or polyvinyl chloride) and is often compounded with a variety of additives and fillers, such as carbon black, plasticizers, antidegradants, fillers and the like. Typically TEO is commercially available as a polypropylene combination of EPDM. Alternatively, the TEO can be formed by the copolymerization of a thermoplastic, for example polypropylene, with a rubberized or rubberized material such as ethylene-propylene rubber. The rubberized material can be either vulcanized or non-vulcanized. The relative proportion of thermoplastic, of Preferably polypropylene to the TEO rubberized material can range from about 15% by weight thermoplastic to about 85% thermoplastic and about 85% rubberized material to about 15% rubberized material respectively. The higher is the amount of thermoplastic, more brittle and more - ^^^^^^^ £ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ A higher amount of rubberized material will make the TEO closer to the rubber in features. The TEO are formulated to produce the desired end-use characteristics. Thus, the various TEOs 5 useful for coatings in the practice of the invention are selected to provide the release coating with expansion and contraction characteristics that correspond to or approximate those of the substrate, preferably a TEO substrate to which it will be adhered. Preferably, the TEO used in the release coating comprises from about 30% to about 70% by weight of thermoplastic and about 70% to about 30% of the rubberized material. More preferably, the TEO comprises of about 40% to about 60% by weight of thermoplastic and about 60% to about 40% by weight of rubberized material. Particularly preferred due to its commercial availability is a TEO comprising polypropylene and ethylene propylene rubber. The ranges Preferred thermoplastics to the rubberized material are particularly suitable for coatings used to protect the tapes of pressure sensitive adhesives on TEO substrates such as those used in many current automotive body side moldings.

In addition to providing the release liner with increased stability at elevated temperatures and improved ability to expand and contract in the heating and contracting with its proposed substrate, a TEO as a component of the release liner can also impart strength to the coating without the use of a woven reinforcing layer (fiber) or non-woven. This is advantageous because the use of other layers can limit the amount of elasticity and flexibility of the release coating and thereby limit the uses of the adhesive article to the pressure sensitive one. The TEOs useful in the practice of the invention include commercially available TEOs such as those available under the trade name DEXFLEX from D & S Plastics Intl. (Auburn Hills, MI), those under the trade name ALCRYN available from Dupont Company (Wilmington, DE), those under the trade name MULTI-FLEX available from Multibase (Copley, OH) and those under the name POLYTROPE TPP available from A. Schulman (Akron, OH). The degree of TEO is selected by the type of process that will be used to make the release coating and is preferably an extrusion grade, such as Dexflex SB-814 available from D &S Plastics Intl. Commercially available TEOs may include other additives such as fillers, processing aids, plasticizers and the like. The release coating of the invention can be made by processes that are known and commercially available. These processes include extrusion of blown film or coextrusion for films having multiple layers and laminar extrusion or coextrusion. Films can be processed in thickness from about 0.00127 cm (0.0005 inch) to about 0.0254 cm (0.010 inch) and preferably in thickness from about 0.00254 cm (0.001 inch) to about 0.02032 cm (0.008 inch). In general, thinner films are desirable for cost considerations, but it may be necessary to use thicker films to obtain certain properties such as tear strength, tensile strength and the like. Various additives can be combined to the TEO resin before extrusion or can be added directly to the extruder. The additives are included in typical amounts for the purpose for which they are designed to include fillers, colorants (for example dyes or pigments), slip agents, antiblocking agents, processing aids and the like.

Anti-blocking agents are particularly useful for outer layers of polyethylene to prevent adhesion or blocking between the polyethylene layers when the extruded film is wound onto a roll. Useful materials include diatomaceous earth by itself or preferably in a low density polyethylene binder. Anti-blocking agents are commonly included in amounts of about 1% to about 20% by weight of the polyethylene resin and preferably in amounts of about 3% to about 8%. The polyethylenes are useful as processing aids to improve the adhesion and film flatness of TEO resins. They can optionally be combined with the TEO to affect the release characteristics of the film. Any type of polyethylene can be used and a low density polyethylene and linear low density polyethylene are preferred. The polyethylenes can be used in amounts of about 1% to 99% by weight and preferably are used in amounts of about 15% or greater. The dyes (for example dyes or pigments) are useful as additives and are commonly used in amounts of from about 0.1% to about 5% by weight of the film composition and preferably from about 0.3% to about 3%.

In one embodiment of the release coating of the invention, the TEO is provided in a core or film core (hereinafter referred to as a TEO film core or simply TEO core) to which a coating 5 or release layer is or It can be applied. The TEO core may consist exclusively of TEO (optionally including additives, fillers or the like) or alternatively it may be a mixture or combination of TEO and one or more other polymers such as polyethylene. In this In this embodiment, it is not necessary that the polymer with which the TEO is combined to form the TEO core be effective in imparting the desired release properties to the film (although it can be), because the release surface is provided by the coating or layer release. Preferably, the TEO core comprises from about 5 wt% to about 100% TEO and more preferably from about 10% to about 100% TEO. The selection of the relative amounts of TEO or other polymers is determined by the properties finishes necessary for the release liner, for example tensile strength, tear resistance, etc. The release coating (described in more detail later herein) is or may be applied to one or both sides of the core of the TEO film depending on the proposed use and the desired release characteristics. Commonly, the release coating for this embodiment is in the form of a layer constituting about 7% to about 15% of the total thickness of the release coating. Where the adhesive is present on a substrate, the TEO core and the release coating are substantially coextensive from beginning to end of at least that portion of the coating that comes into contact with the adhesive coated portion of the substrate. In a second embodiment, the release liner of the invention further comprises a release material such as a polyethylene, polypropylene, fluorocarbon, silicone or combinations (e.g., a mixture) thereof, in such proportion to provide the release surface as an integral part of the release coating. This is preferably obtained by mixing, preferably by combining a TEO with at least one other material selected to impart the desired release properties to the combination of TEO when it is formed into a film; normally, commercially available TEO does not itself provide an appropriate release because it adheres too strongly to the adhesive. However, a TEO can be formulated, for example by varying the amount of thermoplastic such as polyethylene or polypropylene, to ^ ggjliglllg ^^^ ^ provide an integral release surface without the need for combination with other release material. In this embodiment of the invention, the inclusion of a separate surface release coating or layer is optional. Suitable materials with which the TEO can be mixed to integrate the desired release properties into the release coating of the second embodiment include polymers such as polyolefins, preferably polyethylenes and polypropylenes and ethylene copolymers such as ethylene vinyl acetate. Preferably the TEO is mixed with polyethylene. For a release coating of the second embodiment which is particularly useful with acrylic adhesives, a polyethylene is combined with TEO in relative amounts of about 95% to about 50% by weight of polyethylene and about 5% to about 50% by weight of TEO , more preferably about 90% to about 60% by weight of polyethylene and 10% to 40% by weight of TEO. Preferred combinations of TEO and polyethylene provide acceptable release properties of acrylic adhesives without a separate release coating. As the percentage of TEO increases and the percentage of polyethylene decreases, the pressure sensitive adhesive adheres more strongly to the coating and the separation of the coating becomes more difficult. This is particularly true if the adhesive and the coating are heated to an elevated temperature because the heat tends to promote an increase in adhesion of the pressure sensitive additives to the coatings. The polyethylenes useful for the first and second embodiments include high density polyethylenes having a typical density of about 0.96 g / cubic centimeter (grams / cubic centimeter), medium density polyethylenes having a typical density of about 0.93 g / cubic centimeter to about 0.94 g / cubic centimeter, low density polyethylenes having densities of about 0.90 g / cubic centimeter to about 0.92 g / cubic centimeter, linear low density polyethylenes and very low density polyethylenes having densities less than about 0.90 g / cm cubic. In general, the higher the density, the higher the release force needed to separate the coating from a pressure sensitive adhesive. The lower density polyethylenes provide lower release values. The selection of the material depends on the desired release properties. Polyethylenes of different densities may be combined together or may be mixed with ethylene copolymers to provide the desired properties. For example, a combination of high density polyethylene with a low density polyethylene can be used to make a medium density polyethylene having intermediate release values between the high and low density polyethylenes. Another polyethylene useful for use in the TEO blends of the first and second embodiments is a very low density polyethylene formed as a copolymer of ethylene and an alpha olefin having from about 3 to about 10 carbon atoms using a metallocene polymerization catalyst. . Suitable alpha olefins include 1-butene, 1-hexene, 1-octene and combinations thereof. The copolymers have a density of less than about 0.90 g / cm 3, preferably less than about 0.89 g / cm 3 and more preferably less than about 0.88 g / cm 3. The copolymers also have a narrow molecular weight distribution, as defined by having a polydispersity of about 1 to about 4 and preferably about 1.5 to about 3.5. Polydispersity is defined as the ratio of the weight average molecular weight to the number average molecular weight. Additionally, the copolymers can be characterized by an amplitude index of composition distribution (hereinafter referred to as "CDBl"). The CDBl is defined as the weight percent of the copolymer molecule having a comonomer content within 50% (ie +/- 50%) of the average total content of the molar comonomer. The CDBl and the method for its determination are described in U.S. Patent No. 5,206,075, incorporated herein by reference. The CDB1 of suitable copolymers is preferably greater than 70% and more preferably greater than 80%. Appropriate copolymers are commercially available from Exxon Chemical Company under the tradename EXACT and from the Dow Chemical Company under the tradename ENGAGE. The coatings or release layers applied to the TEO film core in the first embodiment preferably include a release material comprising a polyolefin, more preferably polyethylene or polypropylene imparting the desired release characteristics to the coating. Other release materials that can be used as coatings or layers External ones with the first embodiment of the release coating include silicones, for example polysiloxanes, epoxy silicones, also as perfluoroethers, fluorocarbons, polyurethanes and the like. The release materials are known and are described in several sources in which the literature of patents For example, epoxy silicones are described in U.S. Patent Nos. 4,822,687 (Kessel et al.), 5,217,805 (Kessel et al.), 5,576,356 (Kessel et al.). 5,332,797 (Kessel et al.); perfluoropolyethers are disclosed in U.S. Patent No. 4,830,910 (Larson), fluorocarbons in a polymeric matrix are described in U.S. Patent No. 5,110,667 (Galick et al.) and various types of silicones are disclosed in U.S. Patent Nos. 2,588,367 (Dennet ), 3,960,810 (Chandra et al.), 4,162, 356 (Grenoble), 4,306,050 (Koerner et al.); British Patent No. 1,375,792 (Colquhoun et al) and German Patent No. 2,736,499 (Hoc meyer), each of which is incorporated herein by reference. Commercially available release materials are available from various suppliers such as General Electric Company, (Albany, NY) Dow Corning under the trade name SYL-OFF (Midland, MI), Wacher Chemie (Germany) and Th. Goldschmidt AC (Germany) . Coatings are commercially available from Akrosil (Menasha, Wl) and Daubert (Willowbrook, IL). The release materials can be applied to the TEO core as solvent-borne or water-based coatings, solvent-free coatings, heat fusion coatings or can be constructed with the TEO core using conventional processes. Solvent-based and water-based coatings are commonly applied to the TEO core by processes such as roller coating, knife coating, curtain coating, etch coating, coiled rod coating and the like. The solvent or water is then removed by drying in an oven and the coating is optionally cured in the oven. Coatings without solvents include 100% solids compositions such as silicones or epoxy silicones which are coated on TEO by the same types of processes used for coating with solvents and then cured by exposure to ultraviolet light. Optional steps include priming the TEO prior to coating or surface modification of the TEO, such as with corona treatment. Thermal melt coatings such as polyethylenes or perfluoroethers are 100% coatings of their solids that are then heated applied by means of a nozzle or with a heated blade. The thermal fusion coatings are preferably applied by co-extrusion of the release material with the TEO core in blown films or laminar extruder for ease of coating and for process efficiency. The TEO core can be coated on one or both sides to provide a release coating of the first embodiment. The amount of release force, for example the force required to separate the adhesive coating, can range from almost zero to about 67 Kg / m (kilograms / meter) (60 ounces per inch). When the release force is at the highest end of the range, that is, greater than about 56 Kg / m (50 ounces / inch), it is difficult to initiate the removal of the coating, as well as continuing the separation of the coating once a part of the coating has been separated from the adhesive. With high removal forces, the coating may tear or the adhesive may be pulled from the proposed substrate causing distortion or wrinkling of the adhesive and adversely affecting the retention power of the adhesive. The lower end of the removal force range, for example less than about 5.6 Kg / m (5 oz / in) is commonly referred to as the "premium release" and these values are usually obtained with silicone coatings. Sometimes, the premium release may not be desirable if the coating is released too easily and jumps off the adhesive to expose the adhesive to debris and other contamination. Release values of approximately 16 Kg / m (15 ounces / inch) to approximately 50 Kg / m (45 ounces / inch) are suitable for most applications, so that the coating adheres well enough to the adhesive to avoid detachment while still easily separable. The release surface of the release coating of the invention thus preferably exhibits a release value of less than about 67 Kg / m (67 ounces / inch), more preferably less than about 50 Kg / m (45 ounces / inch) ), more preferably less than about 33.5 Kg / m (30 ounces / inch), as measure in the test method of the release force described hereinafter. Where the release material comprises a silicone, the release value of the release surface of the coating is preferably less than about 11 Kg / m (10 Kg / m). ounces / inch), more preferably less than about 5.6 Kg / m (5 ounces / inch). When both sides are coated, the coatings on each side may be the same or may be different to provide differential release.

For differential release, the release liner will have a higher release force on one side than the other. For example, one side of a release liner can be coated with a silicone release material having a release force of a pressure sensitive adhesive of 11 Kg / m (10 ounces / inch) and the other side may have a silicone release material that has a release strength of 22 Kg / m (20 ounces / inch). This ensures that the adhesive will adhere more strongly to one side of the coating than the other, such that when a roll of tape is unwound, the adhesive remains consistently on the same side of the release coating. The coating of the invention is useful for any type of pressure sensitive adhesive used in the industry. This includes pressure sensitive adhesives based on acrylate or acrylics, polyesters, silicones, block copolymers, ethylene vinyl acetate and the like. The selection of the release surface will depend on the type of pressure sensitive adhesive to which it is adhered. For example, release surfaces of polyethylene, polypropylene, perfluoroethers and silicone are useful with acrylate pressure sensitive adhesives and perfluoroethers are useful for silicone pressure sensitive adhesives. Pressure sensitive adhesives useful in the practice of this invention include acrylic adhesives, natural rubber adhesives, adhesive block copolymer adhesives, polyvinyl acetate adhesives, ethylene vinyl acetate adhesives, silicone adhesives, polyurethane adhesives, thermosetting pressure sensitive adhesives, such as epoxy acrylate or pressure sensitive adhesives of epoxy polyester and the like. These types of pressure sensitive adhesives are known in the art and are described in Handbook 5 of Pressure Sensitive Adhesive Technology, Satas (Donatas), 1989, 2a. edition, Van Nostrand Reinhold, also as patent literature. Pressure sensitive adhesives can also include adhesives such as crosslinking agents, fillers, gases, blowing agents, glass or polymeric microspheres, silica, calcium carbonate fibers, surfactants and the like. The additives are included in sufficient quantities to effect the desired properties. The release coating of the invention is preferably used with a thermally stable pressure sensitive adhesive. Thermally stable pressure sensitive adhesives include acrylate pressure sensitive adhesives such as for example those described in Re 24906 (Ulrich), 4,181,752, (Martens et al), 4,818,610 (Zimmerman et al.) And silicone pressure sensitive adhesives. The adhesives can be prepared by any of the known methods in which are included emulsion polymerization, solvent polymerization, beam polymerization electrons, polymerization with ultraviolet light and the i ^ u ^^? t? tv r ^ - ^ tfM na similar. Commonly, acrylate adhesives are homopolymers and copolymers of monofunctional unsaturated acrylic or methacrylic acid ester monomers of non-tertiary alcohols having from about 1 to about 5 carbon atoms and preferably from about 4 to about 12 carbon atoms A comonomer can optionally be included to improve the cohesion strength of the adhesive Such reinforcing comonomers useful in the preparation of copolymers have commonly a vitreous transition temperature of the homopolymer higher than the vitreous transition temperature of the acrylic acid ester copolymer. Suitable acrylic acid ester monomers include 2-ethylhexyl acrylate, acrylate Isooctyl, isononyl acrylate, n-butyl acrylate, decyl acrylate, dodecyl acrylate, octadecyl acrylate and mixtures thereof. Preferred monomers include isooctyl acrylate, n-butyl acrylate and mixtures thereof. Useful reinforcing comonomers include acrylic acid, methacrylic acid, itaconic acid, acrylamide, substituted acrylamides, N-vinyl pyrrolidone, N-vinyl caprolactam, isobornyl acrylate and cyclohexyl acrylate. Preferred comonomers include acid acrylic, N-vinyl caprolactam and isobornyl acrylate.

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In a typical process for making pressure sensitive adhesive transfer tapes, an adhesive composition is coated on a release coating. Then the adhesive is cured to form a gelled film on the coating and the release coating with the adhesive is wound onto a large roll. Alternatively, the adhesive can be coated and cured on a coating and then transferred into a different coating before the conversion. Then the adhesive coated sheet is converted into narrow rolls by cutting the large roll and winding the narrow width tape over the centers for customer use. The coatings of the invention can also be used with foam tapes such as acrylic foam tapes 5605 and 5344 available from the Minnesota Mining and Manufacturing Company (St. Paul, MN), also as tapes coated on both sides. The release coating of the invention is preferably thermally stable (ie, stable to ), that is, retains structural integrity since it will not melt or decompose significantly at elevated temperatures used in the manufacture or processing of a proposed substrate. A preferred release coating retains structural integrity when exposed at temperatures of approximately 90 ° C, more preferably about 120 ° C, more preferably about 150 ° C, for a period of about 20 minutes, more preferably for a period of about half an hour, more preferably for a period of about 1 hour. Substantially, the release coating of the invention does not preferably exhibit shrinkage (dilation) or waviness when brought to room temperature after being exposed to an elevated temperature for an extended period of time. A preferred coating exhibits substantially no shrinkage or shrinkage when brought to room temperature (ie, about 20-25 ° C) after being exposed to a temperature of about 90 ° C, more preferably to about 1320 ° C, more preferably about 150 ° C, for a period of about half an hour, more preferably at about 1 hour. Shrinkage and waviness can be avoided by selecting a release coating that has coefficients of thermal expansion and contraction substantially similar to those of the proposed substrate. The coefficients of expansion and thermal contraction of the release coating are preferably within at least 10% of the coefficients of expansion and thermal contraction of the proposed substrate or article to which an adhesive film comprising the coating is applied.

The preferred embodiments of the release liner of the invention are preferably thermally stable, tear-resistant and / or substantially non-exhibitable. no shrinkage or ripple when brought to room temperature after being exposed to a high temperature for an extended period of time, it will be understood that the present invention will not be unnecessarily limited. Thus, any release coating for use with a pressure sensitive adhesive, such a release coating comprising a TEO, is within the scope of the present invention. The following non-limiting examples further illustrate the present invention. Unless stated otherwise, the following test procedures were used in the examples. The materials and particular amounts thereof cited in these examples, as well as other conditions and details, will be construed to be widely applied in the art and should not be construed to unduly restrict or limit the invention in any way.

TEST METHODS Release Force Samples are prepared by lamination of the release side or coating surface to the adhesive side of a pressure sensitive adhesive tape (acrylic foam tape 5344 from Minnesota Mining and Manufacturing Company, (St. Paul MN) using a manual roller to eliminate air cavities The other side of the tape is protected with a standard polyethylene release liner, strips measuring 2.54 cm wide by 17.8 cm long are cut and then aged for three days at room temperature (approximately 20-25 ° C and tested or aged at 70 ° C for 7 days and tested.) For the test, the standard polyethylene coating is removed and the adhesive tape is laminated to the bed of an IMASS adhesion tester (Imass Inc. Hingham, MA) .The coating is then pulled from the adhesive at a 180 ° angle and a speed of 30 cm / minute.The force required to separate the coating it is reported in ounces / inch.

Tear Resistance A sample of 15.24 cm by 5.08 cm coating is cut to the dimension of 5.08 cm which is the minor axis and the dimension of 15.24 which is the major axis. The major axis is the test direction (on the tape or transverse to the notch of 1.9 cm it is cut from one edge in the middle part of the minor axis and parallel to the major axis of the sample.) The sample is placed in a tensile tester INSTRON (Instron Corp, Canton, MA) having a jaw separation of 2.54 cm, in such a way that the notch is positioned in line with the jaws, the jaws are separated at a speed of 19.7 cm / minute and the average force required to tear the sample The samples are run in the direction of the tape and in the transverse direction of the tape.The test results are recorded in pounds.

Expansion and contraction in a TEO substrate 15 The substrate used in this example is a body side molding (DEXFLEX 777, D &S Plastics Intl., Auburn Hills, MI) of injection molded thermoplastic polyolefin obtained from Lexamar (Boyne City, MY) . The molding is approximately 121 cm (4 feet) long. He the release liner is laminated to an adhesive tape (5344 Acrylic Foam Tape) and a strip of adhesive tape 81 cm (32 inches) long with release liner is applied to the molding. Then the molding is heated to a temperature of 149 ° C for 13 minutes and then cooled to room temperature. The coating is '• ^^^^^. ^^ "fc examined for warts or ripples and in that if the liner has shrunk and left exposed adhesive at the ends of the tape.

EXAMPLE 1 A film was prepared by extruding a combination of 85 parts of TEO (thermoplastic elastomeric olefin) and 15 parts of LLDPE (linear low density polyethylene) and about 1 part of red pigment.

(PM4532 available from Techmer, Clinton, TN) to a thickness of 0.153 mm using a blown film extruder. TEO is a thermoplastic polyolefin having fillers and constituting a combination 50/50 polypropylene and EPDM (diene monomer ethylene propylene). Was obtained as DEXFLEX SB-814 from D &S Plastics Intl. (Now Solvay Engineered Plastics, Auburn Hills, MI). LLPPE was a linear low density polyethylene available as ESCORENE LD117.85 from Exxon Chemical Company (Houston, TX). The blown film extruder was put into operation for obtain melt flow temperatures high enough to provide a uniform flat film. The extruder temperatures ranged from about 177 ° C to about 205 ° C. Then the film was coated on each side with compositions of silicone cured by ultraviolet light available from ^^^^^^^^^^^. ^ .. ^^. ^^^. ^^^^^^ Akrosil to elaborate a release liner. Specifically, one side of the compound was coated with H2C (Akrosil) which had a low release value and the other side was coated with H3D (Akrosil) which has a higher release value. The release liner was tested for the release force on the H3D side. The strength of release after three days at room temperature (approximately 20-25 ° C) was 1.1 Kg / m (0.96 ounces / inch) and after 7 days at 70 ° C, the release force was 2.6 Kg / m (2.3 ounces / inch). The coating was tested for expansion and contraction in a TEO substrate, as described in the above test methods. Does not exhibit any visible shrinkage or wrinkling.

EXAMPLE 2 A 0.153 mm thick film composite was prepared by coextruding 0.127 mm TEO (DEXFLEX SB-814) having approximately 1% red pigment (PM4532) as a core, 0.013 mm LDPE (low density polyethylene). on a surface of the TEO and 0.013 mm of MDPE (medium density polyethylene) on the other surface of the TEO in a blown film extruder. The low density polyethylene had a density of 0.92 g / cubic centimeter and was obtained under the tradename PETROTHENE NA353 from Quantum Chemical Corp. (Cincinnati, OH). The medium density polyethylene had a density of about 0.93 g / cm 3 and consisted of a combination of 33 parts by weight of LDPE (PETROTHENE NA353) and 67 parts of high density polyethylene having a density of 0.96 g / cm 3. It was obtained under the trade name PETROTHENE LT6180 from Quantum Chemical Corporation. The medium and low density polyethylenes provided differential release surfaces for an acrylate pressure sensitive adhesive. He release liner was tested for tear resistance. The coating had a tear resistance in the machine direction of 0.226 Kilograms (0.5 pounds) and a tear strength in the transverse direction of 2.2 Kg (4.9 pounds). The coating was tested for expansion and contraction on a TEO substrate as described in the above test methods. Does not exhibit any visible shrinkage or wrinkling.

EXAMPLES 3-6 A release coating was prepared by combining TEO (DEXFLEX SB-814) with varying amounts of a low density polyethylene as shown in Table 1 and forming a 0.153 mm thick film using a blown film extruder. The TEO was colored with a MiÜBiíiíttii 11 II i || t ^ Mi * ^^ • = ^^ - * ^ "Xí vs ^ .. ^, black pigment of pb.The polyethylene consisted of" * »DOWFLEX 2045 which is a linear low density polyethylene which has a density of 0.92 g / cm 3 and a narrow molecular weight distribution. The coatings were tested for release strength as described above except that the samples were aged in an oven at 121 ° C for 30 minutes and cooled to room temperature before testing. The release values are shown in Table 1. The data shows that in the preferred ranges of TEO and polyethylene (Examples 5 and 6) acceptable release values are obtained (ie, less than about 44.6 Kg / m (40 oz. inch) All the coatings were tested for expansion and contraction on a TEO substrate using the test method described above, none of which exhibits any visible shrinkage or shrinkage.

I revealed it? Complete of all patents, XI ** patent documents and publications cited herein are incorporated by reference. The above detailed description and examples have been provided for clarity and understanding only. Any unnecessary limitation of them will not be understood. The invention is not limited to the exact details shown and described as obvious variations for those skilled in the art will be included in the scope of the invention defined by the claims. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Claims (17)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property. 1. A release liner for use with a pressure sensitive adhesive, the release liner comprises a core and a release layer or coating that provides a release surface for such a core, the release liner is 10 characterized in that the core comprises a thermoplastic elastomeric olefin and such release layer or coating comprises a release material.
2. 2. The release liner according to claim 1, characterized in that it has two 15 main surfaces, wherein at least one of the two main surfaces is the release surface and the release material comprises silicone, polyethylene, polypropylene, fluorocarbon or a combination thereof.
3. 3. The release coating according to claim 1, characterized in that the percentage of thermoplastic elastomeric olefin in such core or such film comprises at least 5% by weight.
4. 4. The compliance release liner 25 with claim 1, characterized in that the percentage This is a thermoplastic elastomeric olefin in such a core or such a film comprises at least 10% by weight.
5. 5. The release liner according to claim 1, characterized in that it is applied to a pressure sensitive adhesive to form an adhesive article.
6. 6. A release liner for use with a pressure sensitive adhesive, the release liner comprises a film having a release surface and is characterized in that the film comprises a thermoplastic elastomeric olefin and a release material, the film imparts strength to tear the release liner without the use of a woven or non-woven reinforcing layer.
7. The release liner according to claim 6, characterized in that it has two main surfaces, wherein at least one of the two main surfaces is such a release surface and such release material comprises silicone, polyethylene, polypropylene, fluorocarbon or a combination of them.
8. The release liner according to claim 6, characterized in that the percentage of thermoplastic elastomeric olefin in such a core or such film comprises at least 5% by weight.
9. 9. The release coating according to claim 6, characterized in that the percentage of thermoplastic elastomeric olefin in such core or such film comprises at least 10% by weight.
10. The release liner according to claim 6, characterized in that it comprises a film comprising a mixture of 5 to 50% by weight of thermoplastic elastomeric olefin and 95 to 50% by weight of a polymer selected from the group consisting of polyethylene , polypropylene, silicone and mixture thereof.
11. 11. An adhesive article characterized in that it comprises a release liner according to claim 1 or 6 applied to a pressure sensitive adhesive.
12. 12. The adhesive article according to claim 11, characterized in that it further comprises a substrate adhered to such pressure sensitive adhesive.
13. 13. The adhesive article according to claim 12, characterized in that said release coating exhibits thermal expansion and contraction properties that match those exhibited by such a substrate, such that such release coating is thermally stable when exposed to a elevated temperature for a period of time and then cooled to room temperature.
14. 14. The adhesive article according to claim 12, characterized in that said substrate comprises a thermoplastic elastomeric olefin.
15. 15. An adhesive article characterized in that it comprises a release coating according to claim 1 or 6 applied to a pressure sensitive adhesive adhered to a substrate, wherein such release coating remains wrinkle-free and coextensive with the adhesive when it is brought to room temperature after exposure of the substrate to which the adhesive article is adhered at temperatures of 90 ° C to 150 ° C for periods up to half an hour or one hour or more.
16. 16. A method for using a release coating characterized in that it comprises: (a) applying a pressure sensitive adhesive reinforced with a release coating to a substrate, said release coating includes a film comprising a thermoplastic elastomeric olefin; (b) heating such a substrate having the pressure sensitive adhesive and release coating adhered thereto and (c) cooling such a substrate having the pressure sensitive adhesive and release coating adhered thereto, such that the coating of release does not wrinkle or shrink substantially from the pressure sensitive adhesive. The method according to claim 16, characterized in that during such a heating step, such a substrate having the pressure sensitive adhesive and release coating adhered thereto is heated to an elevated temperature in the range of 90 ° C to 150 ° C and during such a cooling step, such a substrate having the pressure sensitive adhesive and release coating adhered thereto is cooled to room temperature. ^ RELEASE COATINGS FOR ADHESIVES SENSITIVE TO THE A release liner is disclosed for use with a pressure sensitive adhesive. The release coating includes a film of a thermoplastic elastomeric olefin.