Patent Application
20070264468
This invention relates to coextruded multilayer films, and more particularly to coextruded multilayer films having an opacity of at least about 75%.
A variety of polymer films have been typically used for signs in graphic applications. One polymer film that is typically used in these graphic applications is a calendered or dispersion cast polyvinylchloride (PVC) film. While the use of these PVC films has met with success in the marketplace, the films have not been entirely acceptable because they are environmentally unfriendly. Many of the PVC films employ plasticizers that migrate into adhesive layers joined thereto and degrade the functionality of the adhesive composite. Plasticizer migration is also considered to be related to objectionable spotty film appearance, sometimes referred to as mottle. This problem especially is troublesome in warm weather climates. There is also a need for films useful in window graphic applications which require the same color on both sides of the film. In these applications, the graphic may be put on the outside or the inside of the window. In some applications, the films utilized for window graphics comprise at least three layers of coextruded polyolefin, and when the films utilize organic pigments for colors such as red, orange, and yellows rather than the chromium, lead and cadmium heavy metal pigments, the films become quite expensive for use. Accordingly, there is a need for multilayer films for use in signage and graphic applications, automotive synthetic paints, decaling and banner materials which utilize organic pigments, but at reduced costs.
This invention relates to a coextruded multilayer film having an opacity of at least about 75% and comprising:
(A) an opaque thermoplastic polymer core having a first outer surface and a second outer surface;
(B) a first pigmented color layer overlying the core and having a first surface and a second surface; and
(C) a second pigmented color layer underlying the core and having a first surface and a second surface
wherein the composition of the core is different from the compositions of the first and second color layers, and the first and second color layers are not black or gray.
In one embodiment, the opaque core comprises at least one thermoplastic polymer and white pigment, black pigment, or a compounded mixture of white and black pigments, and the first pigmented color layer and the second pigmented color layer contain organic pigments. The coextruded opaque multilayer films of the invention also may comprise in an embodiment a first and/or second skin layers overlying respectively the first and/or second pigmented color layers, in another embodiment a layer of adhesive underlying the second pigmented color layer, and in a further embodiment a release liner underlying the layer of adhesive.
By utilizing inexpensive pigments to provide the opaque polymer core, the color layer thickness can be reduced while maintaining the desired overall opacity and color. Accordingly, desired opaque color films can be prepared at reduced costs. In an embodiment of the present invention, a method to vary the color of the outer surfaces of a multilayered opaque film, comprises providing an opaque multilayered film comprising (A) an opaque core having a first outer surface and a second outer surface, and comprising at least one thermoplastic polymer and white, black, or a compounded mixture of white and black pigments; (B) a first pigmented color layer overlying the core and having a first surface and a second surface; and (C) a second pigmented color layer underlying the core and having a first surface and a second surface wherein the composition of the core is different from the compositions of the first and second color layers, the first and second color layers are not black or gray, and the film has an opacity of at least 75%, and wherein the shade or lightness of the core can be varied from white to black.
The coextruded opaque multilayer films of the present invention, in one embodiment, have an opacity of at least about 75% and comprise:
(A) an opaque thermoplastic polymer core having a first outer surface and a second outer surface;
(B) a first pigmented color layer overlying the core and having a first surface and a second surface; and
(C) a second pigmented color layer underlying the core and having a first surface and a second surface
wherein the composition of the core is different from the compositions of the first and second color layers, and the first and second color layers are not black or gray.
In one embodiment, the coextruded opaque multilayer film comprises three layers as described above, namely, an opaque thermoplastic core layer and first and second pigmented color layers on the two surfaces of the core layer, provided that the first and second color layers are different from the core and are not black or gray. The core can differ in composition from the color layers based on thermoplastic polymer composition to include amount and type of thermoplastic polymer, additive composition to include amount and type of an additive such as e.g. a pigment, or a combination thereof. In an embodiment of the invention the core can differ in composition from the color layers in the amount of pigment, the color of pigment, or a combination thereof. In several embodiments of the invention the core can differ from the color layers in composition by containing a greater amount of pigment than the color layers, by containing a greater amount of pigment than the color layers where the pigment in the core is different in color from the pigment in the color layers, or by containing a greater amount of pigment than the color layers where the pigment in the core is different in color from the pigment in the color layers and where the color of the core can range in shade or lightness from white through various shades of gray to black. Thus, the core in one embodiment may have any color such as white, black, gray, red, orange, etc. In one embodiment, the opaque thermoplastic polymer core comprises a thermoplastic polymer and an inexpensive inorganic pigment such as a white pigment, black pigment or a compounded mixture of white and black pigment to produce a gray color. Such a three layer film is illustrated in
The thermoplastic polymer utilized in the opaque core may comprise one or more thermoplastic polymers and, in another embodiment, the thermoplastic polymer can have a melting point in the range of from about 70° C. to about 175° C. The thermoplastic polymer can comprise a polyolefin which can be prepared from alkenes having 2-30 carbon atoms where the polyolefin can comprise a homopolymer and/or copolymer from 2 or more alkene monomers such as e.g. a polypropylene homopolymer or a linear low density polyethylene; a poly(alkyl (meth)acrylate) which can comprise a poly(alkyl methacrylate) such as e.g. a poly(ethyl methacrylate), a poly(alkyl acrylate), a copolymer of an alkyl methacrylate and an alkyl acrylate, or mixtures thereof; a styrene-based homopolymer or copolymer; a halocarbon polymer such as a poly(vinyl chloride); a polyamide; a polyurethane; an alkene-vinyl carboxylate copolymer such as e.g. an ethylene-vinyl acetate (EVA) copolymer; an acrylonitrile-based homopolymer or copolymer; a cyclic olefin homopolymer or copolymer; an ionomer comprising a metal-containing salt of an alkene-(meth)acrylic acid copolymer; a polyester, or a combination of any of the foregoing thermoplastic polymers. In an embodiment of the invention the core can comprise at least one polyolefin. Examples of useful thermoplastic polymers include polyolefins such as polyethylene, polypropylene, polybutylene, and copolymers of ethylene, propylene or butylene with an alpha olefin or blends of two or more thereof. The alpha olefin is selected from those alpha olefins containing from about 2 to about 18 carbon atoms and in one embodiment from about 4 to 12 carbon atoms. In the further embodiment, the alpha olefins contain from about 4 to 8 carbon atoms. Examples of useful alpha olefins include 1-butene, 1-hexene, 4 methyl-1 pentene, and 1-octene. The polyolefins useful in the core may be made from a blend of polyolefins such as a polyethylene and an ethylene-propylene copolymer. Very low density polyethylenes (VLDPE), low density polyethylenes (LDPE), medium density polyethylenes (MDPE), linear low density polyethylenes (LLDPE), high density polyethylenes (HDPE), and blends of two or more thereof also are useful. Specific examples of useful polyolefins include those prepared using a Ziegler-Natta catalysts or a metallocene catalysts. A variety of useful polyolefins are available from Huntsman Products, and a specific example includes Huntsman MDPE PE-1080 which is identified as a polyethylene having a density of 0.93 g/cc.
The thermoplastic polymers included in the core in another embodiment may comprise polyolefin elastomers which have been referred to as plastomers. In one embodiment, the polyolefin elastomers have a melt flow index from about 1 to about 100, or from about 3 to about 35, or from about 5 to about 25 g/10 min. The melt flow index is determined by ASTM test D-1238 at 190° C. In one embodiment, the melt flow index for a polyolefin elastomer is in the range from about 1 to about 25, or from about 2 to about 10 g/10 min. In another embodiment, the polyolefin elastomers have a molecular weight of about 5,000 to about 50,000, or of about 20,000 to about 30,000. Densities of the polymers and copolymers described herein are determined in accordance with ASTM D1505. The polyolefin elastomers include polyolefin polymers which exhibit both thermoplastic and elastomeric characteristics. These elastomers include copolymers and terpolymers of ethylene with one or more alpha-olefins containing 3 or more carbon atoms, and copolymers and terpolymers of propylene with one or more alpha olefins containing 2 or 4 or more carbon atoms. The copolymers typically comprises from about 2% to about 30%, or from about 5% to about 25%, or from about 10% to about 20% by weight of the alpha-olefin. The alpha olefins include ethylene, propylene, 1-butene, isobutylene 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 1-dodecene. Particularly useful alpha olefins include 1-butene, 1-hexene and 1-octene. Polyolefin elastomers include but are not limited to ethylene-butene copolymers, ethylene-octene copolymers, ethylene-hexene copolymers, and ethylene-hexene-butene terpolymers, as well as mixtures thereof. The copolymers and terpolymers may be obtained by copolymerization of ethylene or propylene with an alpha olefin, such as 1-butene, using single-site metallocene catalysts. Such copolymers are available from Exxon Mobil Chemical Company under the general trade designation EXACT, and Dow Chemical Company under the general trade designation AFFINITY. Another useful propylene and 1-butene copolymer is available commercially from Basell under the trade designation EP3C30HF. This copolymer has 14% polybutene and a melt flow index of about 5.5 g/10 min. Non-limiting examples of polyolefin elastomers from Exxon Mobil Chemical Company include: linear ethylene-butene copolymers such as EXACT 3024 having a density of about 0.905 gms/cc and a melt index of about 4.5 g/10 min. EXACT 3027 having a density of about 0.900 gms/cc and a melt index of about 3.5 g/10 min. EXACT 4011 having a density of about 0.888 gms/cc and a melt index of about 2.2 g/10 min. and EXACT 4049 having a density of about 0.873 gms/cc and a melt index of about 4.5 g/10 min. and ethylene-hexene copolymers such as EXACT 4150 having a density of about 0.895 gms/cc and a melt index of about 3.5 g/10 min. Other non-limiting examples of useful EXACT plastomers are EXACT 3017 and EXACT 4053. Plastomers sold by Dow Chemical Co. under the tradename AFFINITY are believed to be produced in accordance with U.S. Pat. No. 5,272,236. In one embodiment, these plastomers are substantially linear polymers having a density of about 0.85 gms/cc to about 0.97 g/cc measured in accordance with ASTM D-792, a melt index (“MI”) of about 0.01 gms/10 minutes to about 1000 grams/10 minutes, a melt flow ratio (110/12) of about 7 to about 20, where 110 is measured in accordance with ASTM D-1238 (190/10) and 12 is measured in accordance with ASTM D-1238. These plastomers include homopolymers of C2-C20 olefins such as ethylene, propylene, 4-methyl-1-pentene, and the like, or they can be interpolymers of ethylene with at least one C3-C20 alpha-olefin and/or C2-C20 acetylenically unsaturated monomer and/or C4-C18 alpha-olefins. These plastomers generally have a polymer backbone that is either unsubstituted or substituted with up to 3 long chain branches/1000 carbons. As used herein, long chain branching means a chain length of at least about 6 carbons, above which the length cannot be distinguished using C13 nuclear magnetic resonance spectroscopy. Useful AFFINITY plastomers are characterized by a saturated ethylene-octene backbone, and a narrow level of crystallinity. These plastomers also are compatible with pigments, brightening agents, fillers such as carbon black, calcium carbonate and silica, as well as with plasticizers such as paraffinic process oil and naphthenic process oil. Other commercially available plastomers may be useful in the invention, including those manufactured by Mitsui. Non-limiting examples of plastomers available from Dow include AFFINITY PF 1140 having a density of about 0.897 gms/cc, and a melt flow index of about 0.5 g/10 mins; AFFINITY PF 1146 having a density of about 0.90 gms/cc, and a melt index of about 1 gms/10 min; AFFINITY PL 1880 having a density of about 0.902 gms/cc, and melt index of about 1.0 gms/10 min; AFFINITY EG 8100 having a density of about 0.87 gms/cc, and a melt index of about 1 gms/10 min.; AFFINITY EG 8150 having a density of about 0.868 gms/cc, and a melt index of about 0.5 gms/10 min,; AFFINITY EG 8200 having a density of about 0.87 gms/cc, and a melt index of about 5 g/10 min.; and AFFINITY KC 8552 having a density of about 0.87 gms/cc, and a melt index of about 5 g/10 min. Terpolymers of e.g. ethylene, butene and hexene also can be used in the core of the multilayer films of the invention. Examples of terpolymers are Exxon's EXACT 3006 (an ethylene-butene-hexene terpolymer with a density of 0.910 g/cm3 (g/cc) and M.F.I. of 1.2 g/10 min (g/10′)); EXACT 3016 (an ethylene-butene-hexene terpolymer having a density of 0.910 g/cm3 (g/cc) and a M.F.I. of 4.5 g/10 min (g/10′)); EXACT 3033 (an ethylene-butene-hexene terpolymer having a density of 0.900 g/cm3 (g/cc) and a M.F.I. of 1.2 g/10 min (g/10′)); and EXACT 3034 (an ethylene-butene-hexene terpolymer having a density of 0.900 g/cm3 (g/cc) and a M.F.I. of 3.5 g/10 min (g/10′)). Examples of useful terpolymers available from Dow include AFFINITY PL 1840 (an ethylene-propylene-butylene terpolymer); AFFINITY PL 1845 (an ethylene-propylene-butylene terpolymer); and AFFINITY PL 1850 (an ethylene-propylene-butylene terpolymer). In one embodiment, the polyolefin elastomers useful in the core of the multilayer films of the invention include those formed by a single-site metallocene catalyst such as those disclosed in EP 29368, U.S. Pat. No. 4,752,597, U.S. Pat. No. 4,808,561, and U.S. Pat. No. 4,937,299. As is known in the art, plastomers can be produced by metallocene catalysis using a high pressure process by polymerizing ethylene in combination with other monomers such as butene-1, hexene-1, octene-1 and 4-methyl-1-pentene in the presence of catalyst system comprising a cyclopentadienyl-transition metal compound and an alumoxane.
The thermoplastic polymer of the core of the multilayer films of the invention may, in one embodiment, comprise at least one propylene homopolymer, propylene copolymer or blend of two or more thereof. A number of useful propylene homopolymers are available commercially from a variety of sources, and these include: 5390N (Dow Chemical), SE66R (Dow Chemical), 3622 (Atofina), 3576X (Atofina), Moplen HP400N (Basell), P4G4K-038 (Huntsman), and 9074 MED (Exxon Mobil). In one embodiment, useful propylene copolymers may comprise polymers of propylene and up to about 40% by weight of at least one alpha-olefin selected from ethylene and alpha-olefins containing from 4 to about 12, or from 4 to about 8 carbon atoms. Examples of useful alpha-olefins include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. In one embodiment, the polymers of propylene which are utilized in the present invention comprise polymers of propylene with ethylene, 1-butene, 1-hexene or 1-octene. The propylene alpha-olefin polymers useful in the present invention include random as well as block copolymers although the random copolymers generally are particularly useful. In one embodiment, the films are free of impact copolymers. Blends of two or more propylene copolymers as well as blends of the propylene copolymers with propylene homopolymers can be utilized. In one embodiment, the propylene copolymers are propylene-ethylene copolymers with ethylenic contents from about 0.2% to about 10% by weight. In another embodiment, the ethylene content is from about 3% to about 10% by weight, or from about 3% to about 6% by weight. With regard to the propylene-1-butene copolymers, 1-butene contents of up to about 15% by weight are useful. In one embodiment, the 1-butene content generally may range from about 3% by weight up to about 15% by weight, and in other embodiments, the range may be from about 5% to about 15% by weight. Propylene-1-hexene copolymers may contain up to about 35% by weight 1-hexene. In one embodiment, the amount of 1-hexene is up to about 25% by weight. Propylene-1-octene copolymers useful in the present invention may contain up to about 40% by weight of 1-octene. More often, the propylene-1-octene copolymers will contain up to about 20% by weight of 1-octene. The propylene copolymers useful in preparing the film facestock of the present invention may be prepared by techniques well known to those skilled in the art. For example, the copolymers useful in the present invention may be obtained by copolymerization of propylene with an alpha-olefin such as ethylene or 1-butene using single-site metallocene catalysts. Some useful commercially available propylene copolymers include: DS6D21 (Dow Chemical), KB4560 (BP Amoco), KB4586 (BP Amoco), KB4986 (BP Amoco), 9433 (BP Amoco), 13T25A (Huntsman), P5M4K-046 (Huntsman), and P5M5K-047 (Huntsman).
In one embodiment, the core comprises, in addition to one or more polyolefins, a second thermoplastic polymer material comprising an alkene-vinyl carboxylic acid ester copolymer such as e.g. an ethylene-vinyl acetate copolymer, an alkene-unsaturated carboxylic acid or anhydride copolymer such as e.g. an ethylene-acrylic acid copolymer or an ethylene-methacrylic acid copolymer, an ionomer derived from metal including sodium, lithium or zinc and an alkene-unsaturated carboxylic acid or anhydride copolymer such as e.g. a sodium salt of an ethylene-methacrylic acid copolymer, an alkene-alkyl unsaturated carboxylic acid ester copolymer such as e.g. an ethylene-methyl acrylate or methacrylate copolymer, or combinations of two or more thereof. The concentration of the second thermoplastic polymer material in the core may range from about 1% to about 40%, and in one embodiment is from about 2% to about 30% by weight based on the weight of the core. Examples of ethylene-vinyl acetate copolymers that can be utilized as the second polymer in the core include those available from DuPont under the trade designation Elvax. Examples include Elvax 3169 (18% VA, MI=1.5) Elvax 3170 (18% VA, MI=2.5) and Elvax 3174 (17% VA, MI=8.0). Other useful commercially available ethylene-vinyl acetate copolymers include EQUISTAR EVA 240F (available from EQUISTAR and containing 18% VA), and AT Plastics EVA 1821 which contains 18% vinyl acetate. The ionomer resins are available, for example, from DuPont under the tradename Surlyn. These resins are identified as being derived from sodium, magnesium, lithium or zinc and copolymers of ethylene and methacrylic acid. Included in this group are: the sodium containing ionomers available under the Surlyn name with the following designations: 1601, 1605, 1707, 1802, 1901 AD-8548, 8020, 8140, etc. Examples of zinc containing ionomers available under the Surlyn name are 1650, 1652, 1702, 1705, 1855, 1857, 9950, 9970, etc. Lithium containing ionomers are available from DuPont under the Surlyn name include AD-8546, 7930 and 7940. Useful ionomer resins also are available from A. Schulman under the tradename Clarix, and from Exxon Mobil under the tradename Iotek. Ethylene-methacrylic acid copolymers are available, for example, from DuPont under the tradename Nucrel. Specific examples include Nucrel 0407 which has a methacrylic acid content of 4% by weight and a melting point of 109° C., and Nucrel 0910 which is a methacrylic acid content of 8.7% by weight and a melting point of 100° C. Ethylene-acrylic acid copolymers that are useful include copolymers available from Dow Chemical under the tradename Primacor. These include Primacor 1430 which has an acrylic acid monomer content of 9.5% by weight and a melting point of 97° C.
As noted above, the core of the multilayer film of the present invention is opaque. In one embodiment, the core is rendered opaque by the inclusion of one or more pigments into the thermoplastic polymer. The amount of pigment included in the core may vary over a wide range provided that the core is opaque and the multilayer film incorporating the core has an opacity of at least about 75%, and in other embodiments of the film can have an opacity of at least 80%, 85%, or 90%. The pigments which may be included in the core may be metallic pigments, metallic powders such as aluminum, heavy metal-based pigments, heavy-metal free pigments or organic pigments. A heavy metal is defined herein as including lead, cadmium, chromium or antimony. The metallic pigments include titanium dioxide, both rutile and anatase crystal structure. The titanium dioxide may be coated or uncoated (e.g., aluminum oxide coated titanium dioxide). In one embodiment, the pigments utilized in the core are either non-heavy metallic or organic pigments. Since color layers of the desired color are used on both sides of the core, the core can be rendered opaque by incorporating relatively inexpensive pigments such as carbon and the non-heavy metal pigments. Examples of white pigments which can be utilized in the present invention include metallic pigments such as Polybatch White P8555 SD, available from A. Schulman Inc. and which is identified as a white color concentrate having a coated rutile titanium dioxide concentration of 50% by weight in a propylene homopolymer carrier resin; and Ampacet 110235 which is a white pigmented polyethylene concentrate available from the Ampacet Corporation; and Ampacet 110868. Examples of black pigments useful in the core of the multilayer films of the present invention include various carbon blacks and organic concentrates such as Ampacet 190303 which is a black pigmented polyethylene resin concentrate, and Ampacet 190671A, another black pigmented resin concentrate from Ampacet Corporation. The pigments included in the core of the multilayer films of the present invention may be selected to provide a gray color to the core. The gray color may be obtained from a suitable compounded mixture of white and black to provide the desired shade of gray. Examples of a commercially available gray concentrate are Ampacet 190697 and Ampacet 190870. Other color pigments can be utilized to provide an opaque core having the desired opacity and color. Examples of organic pigment concentrates that can be utilized in the core include Ampacet 150623, a red pigmented polyethylene resin concentrate; Ampacet 150380, a red pigment concentrate, Ampacet 150703 Red PE MB; Ampacet 150623 Red UV PE MB; Ampacet 130283 Yellow UV PE MB; Ampacet 140085 Orange PE MB; Ampacet Dark Green 170560; Ampacet Olympic Blue 160972; and Ampacet Sapphire Blue 160904. An example of a heavy metal containing pigment useful in the core of the multilayer film of the present invention is Ampacet LP20631 Orange PE MB which is identified as a lead molybdate/lead chromate pigment concentrate.
In one embodiment, the pigment may be added to the core material in the form of a concentrate containing the pigment in a resin carrier. The concentrate may contain, for example, from about 20% to about 80% of pigment and from about 20% to about 80% by weight of resin carrier. The resin carrier can be any thermoplastic polymer having a melting point in the range of from about 70° C. or 75° C. to about 175° C. Examples include polyolefins such as polyethylene, polypropylene, polybutylene, etc., and functional copolymers such as ethylene-methacrylate copolymers, ethylene-vinyl acetate copolymers and ethylene acrylic acid copolymers, etc.
In one embodiment, the core utilized in the multilayer films of the present invention also may contain at least one processing aid which is useful in facilitating extrusion. Examples of useful processing aids include fluororine-containing polymers such as e.g. hexafluorocarbon polymers. An example of a commercially available processing aid is Ampacet 10919 which is a product of Ampacet Corporation and is identified as a hexafluorocarbon polymer. Another useful processing aid is Ampacet 401198. The processing aids, when used, are typically included at concentrations of up to about 1.5% or from about 0.5% to about 1.2% by weight.
In another embodiment, the core may comprise in addition to the thermoplastic polymers, pigments, etc. described above, reclaimed or scrap thermoplastic materials, including reclaimed opaque thermoplastic materials. Reclaimed scrap or trimmings from previously coextruded films of the invention can be reground and combined with the virgin material used to form the core. In one embodiment, up to about 20% or even 90% by weight of reground trim scrap or reprocessed trim scrap in a form of re-pelletized trim scrap or just scrap pellets can be included in the core. In another embodiment, from about 1% to about 20% by weight of reclaimed scrap can be included in the core. The reground scrap serves as an inexpensive filler.
As noted above, the coextruded multilayer films of the present invention contain, in addition to (A) an opaque thermoplastic polymer core having a first outer surface and a second outer surface, (B) a first pigmented color layer overlying the core, and (C) a second pigmented color layer underlying the core wherein the composition of the core is different from the compositions of the first and second color layers, and the first and second color layers are not black or gray. The first and second pigmented color layers can comprise one or more thermoplastic polymers, as described hereinabove for the core, and one or more pigments, as described hereinabove for the core, provided that the color of the first and second pigmented color layers are not black or gray. Accordingly, the first and second pigmented color layers may be, for example, white, red, blue, yellow, green, orange, etc. Any of the thermoplastic polymers (and combinations thereof) described above as useful in the core may be utilized in forming the first and second pigmented color layers. Thus the thermoplastic polymer of these color layers may comprise one or more polyolefins with or without a second thermoplastic polymer (e.g., EVA) as described for the core.
Any of the color pigments described above as being useful in the core (except for black and gray) may be utilized in the first and second pigmented color layers, and the amounts of pigment included in the first and second pigmented color layers is an amount which provides the desired color and hue to the layers. In one embodiment of the invention, the colors of the first and second pigmented color layers are the same. In another embodiment of the invention, the colors of the first and second pigmented color layers are different. Specific examples of opaque three layered films in accordance with one embodiment of the present invention include films having: a black core and white layers on both sides of the core; a gray core with white layers on both sides; a black core and red layers on both sides; a white core with red layers on both sides; gray core with red layers on both sides, a white or gray or black core with a red color layer on one side and a green color layer on the other side; etc. The color of the film can be varied in terms of lightness, redness and greenness, and blueness and yellowness by varying the amount and type of pigment in an opaque core, the amount and type of pigment in pigmented color layers, and the thickness of the pigmented color layers. For example in one embodiment of the invention a film comprises a black core and white layers on either side of the core, and the overall color of the film can be manipulated to be various shades of gray depending on the amount of black concentrate in the core, the thickness of the core, the amount of white concentrate in the white layers, and the thickness of the white layers.
In several embodiments of the invention, the inventive film can range in thickness from 0.5 to 12 or 16 mils, 1 to 10 mils, 1 to 8 mils, 3 to 6 mils, 2 to 5 mils, or 1 to 2.5 mils. The thickness of the component layers of the inventive film can also vary. In one embodiment of this invention the core is thicker than the first or the second pigmented color layer, and in another embodiment of the invention the thickness of the core is about equal to or less than the thickness of the first or second pigmented layer. In several embodiments of the present invention the thickness of the core can range from 0.25 to 10 mils, 0.5 to 6 mils, 1 to 4 mils, or 0.25 to 0.75 mil. In several other embodiments of the invention the thickness of the first or the second pigmented color layer can range from 0.1 to 3 mils, 0.2 to 2 mils, or 0.3 to 1 mil.
The core of the multilayer film of the present invention may comprise a monolayer or multilayers where the multilayers are 2 or more layers. The multilayer film of the present invention, which comprises an opaque thermoplastic polymer core and first and second pigmented color layers on either side of the core, may be prepared by using techniques well known to those skilled in the art to include extrusion, coextrusion, lamination, coating, and any combination of the foregoing techniques. In one embodiment, the inventive film can be prepared by extrusion or coextrusion at temperatures between about 175° C. up to about 550° C., or from about 200° C. to about 250° C. The inventive film can also be oriented or nonoriented. The oriented film can be uniaxially oriented or biaxially oriented. The uniaxially oriented film can be machine direction oriented. The oriented film can also be heat set (annealed) or can be heat set to provide for dimensional stability of the film if the film is exposed to heat (temperatures above ambient) during further processing and/or service conditions. In several embodiments of this invention, the inventive multilayer film can be prepared by coextrusion and nonoriented, or can be prepared by coextrusion and uniaxially oriented in the machine direction and heat set to provide for dimensional stability.
The multilayer film of the present invention can also comprise one or two skin layers. The inventive film can comprise a first and/or second skin layers overlying the first and/or second pigmented color layers, respectively. An embodiment of this invention is illustrated in
The layers of the inventive film can also comprise one or more light stabilizers comprising an ultraviolet (UV) light absorber and/or other light stabilizers. In several embodiments of the invention one or both skin layers, one or both pigmented color layers, or any combination of the foregoing layers can each comprise one or more light stabilizers. The one or more light stabilizers can be present in each of the layers of the inventive film on a weight basis at 1,000 to 20,000 ppm (parts per million). Useful light stabilizers can include hindered amine light stabilizers. Hindered amine light stabilizers are described in the literature such as in U.S. Pat. No. 4,721,531, columns 4 to 9. The hindered amine light stabilizers may, for example, be derivatives of 2,2,6,6-tetraalkyl piperidines or substituted piperizinediones. A number of hindered amine light stabilizers useful in the invention are available commercially such as from Ciba-Geigy Corporation under the general trade designations “Tinuvin” and “Chemissorb”, and from Cytec under the general designation “Cyasorb-UV.” Examples include Tinuvin 783 which is identified as a mixture of poly [[60-[(1,1,3,3,-tetramethyl butyl)amino]-1,3,5-triazine-2,4-diyl][[2,2,6,6-tetramethyl-4-piperidyl)imino)hexamethylene [(2,2,6,6-tetramethyl-4-piperidyl)imino]] and dimethyl succinate polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol; Tinuvin 770 which is identified as bis-(2,2,6,6-tetramethyl-4-piperidinyl)-sebacate; Tinuvin 765 which is identified as bis-(1,2,2,6,6-pentamethyl-4-piperidinyl)-sebacate; Tinuvin 622 which is a polyester of succinic acid and N-beta-hydroxy ethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidine; and Chemissorb 944 which is poly[6-(1,1,3,3-tetramethyl butyl)amino]-s-triazine-2,4-diy[[2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene (2,2,6,6-tetramethyl-4-piperidyl)imino]. A useful stabilizer is available under the tradename Ampacet 10561 which is identified as a UV stabilizer concentrate containing 20% by weight of a UV stabilizer and 80% by weight of a low density polyethylene carrier resin; the UV stabilizer in this product is Chemissorb 944. Useful light stabilizers are also provided in Ampacet 150380 and Ampacet 190303, both of which are color pigment concentrates discussed above. Ampacet 150380 has a UV stabilizer concentration of 7.5% by weight. Ampacet 190303 has a UV stabilizer concentration of 4% by weight. The UV stabilizer in each of these products is Chemissorb 944. Ampacet LR-89933 is a grey concentrate having a UV stabilizer concentration of 4.5% by weight, the UV stabilizer being Tinuvin 783.
The skin layers also may contain antiblock and/or slip additives. These additives reduce the tendency of the film to stick together when it is in roll form. The antiblock additives include natural silica, diatomaceous earth, synthetic silica, glass spheres, ceramic particles, etc. The slip additives include primary amides such as stearamide, behenamide, oleamide, erucamide, and the like; secondary amides such as stearyl erucamide, erucyl erucamide, oleyl palimitamide, stearyl stearamide, erucyl stearamide, and the like; ethylene bisamides such as N,N□-ethylenebisstearamide, N,N□-ethylenebisolamide and the like; and combinations of any two or more of the foregoing amides. An example of a useful slip additive is available from Ampacet under the trade designation 10061; this product is identified as a concentrate containing 6% by weight of a stearamide slip additive. The antiblock and slip additives may be added together in the form of a resin concentrate. An example of such a concentrate is available from DuPont under the tradename Elvax CE9619-1. This resin concentrate contains 20% by weight silica, 7% by weight of an amide slip additive, and 73% by weight of Elvax 3170 (a product of DuPont identified as an ethylene/vinyl acetate copolymer having a vinyl acetate content of 18% by weight). The antiblock additive can be used at a concentration in the range of up to about 1% by weight, and in one embodiment about 0.01% to about 0.5% by weight. The slip additive can be used at a concentration in the range of up to about 1% by weight, and in one embodiment about 0.01% to about 0.5% by weight. Another use for slip additives is to impart scuff resistance to the surface of the skin layer. When these materials are incorporated in the skin layer, these materials will migrate to the surface of the skin layer. Alternatively, slip additives can be applied or coated to the top of the skin layer. The slip additive can be incorporated into the skin layer as a polyethylene concentrate or by direct feeding of these additives through the ports of the skin extruder.
As noted, in one embodiment, the coextruded multilayer films of the present invention may comprise:
(A) an opaque core having a first outer surface and a second outer surface, and comprising at least one thermoplastic polymer and white, black or a compounded mixture of white and black pigments;
(B) a first pigmented color layer overlying the core and having a first surface and a second surface; and
(C) a second pigmented color layer underlying the core and having a first and second surface,
wherein the composition of the core is different from the compositions of the first and second color layers, and the first and second color layers are not black or gray. In one embodiment, the first and second pigmented color layers are in direct contact with the first and second outer surfaces of the core, respectively. In other embodiments, intermediate or tie layers or adhesion promoting layers may be incorporated between the outer surface of the core and the pigmented color layers. In an embodiment of this invention the inventive film comprises a core comprising a compounded mixture of white and black pigments, first and second pigmented color layers overlying the outer surfaces of the core where the color layers are the same in color and the color layers are not gray or black, and first and second skin layers overlying the surfaces of the first and second pigmented layers respectively where the skin layers are transparent.
In one embodiment, the core of the multilayer film described immediately above comprises a multilayer film comprising a black or gray base layer and white intermediate layers on both surfaces of the base layer. Thus, the multilayer film of this embodiment comprises at least five layers: a three layer core containing a central black or gray base layer and white intermediate layers overlying or in contact with both surfaces of the base layer; and first and second pigmented color layers overlying the two white intermediate layers. Through the use of the black or gray base layer and the white intermediate layers on both surfaces of the base layer, an opaque multilayer film having colored outer surfaces (same or different color) can be prepared having the desired opacity, thickness, color and hue while using reduced amounts of the color pigments which are more expensive than the black and white pigments used in the base and intermediate layers. Also, it has been observed that the color of the color layers can be shifted and controlled as desired by varying the shade of the core from white to various shades of gray to black. This embodiment is illustrated in
In another embodiment, first and/or second skin layers may be applied over the first and second pigmented color layers, respectively, of the above described five layer film thereby producing a seven layer film as illustrated in
The multilayer films of the invention, whether three layers, five layers, seven layers, or more, can be prepared by coextrusion using coextrusion techniques well known to those skilled in the art. In one embodiment, the coextruded film is not oriented, and in other embodiments, the coextruded film may be oriented in the machine direction only, or oriented in both the machine and the transverse directions, and thereafter annealed or heat set.
The following examples are provided to illustrate the multilayer films of the present invention. Unless otherwise indicated in the examples and elsewhere in the written description and claims, all parts and percentages are by weight, degrees are in centigrade and pressure is at or near atmospheric pressure. The multilayer films illustrated in the following examples are prepared by coextrusion.
Core (0.50 mil)
2% Ampacet Black 190671A
25% Equistar EVA 242F
72% Huntsman MDPE PE-1080
1% Ampacet Process Aid Conc. 10919
First Color Layer (0.6 mil)
20% Ampacet White 110868
25% AT Plastics EVA 1821
54% Huntsman MDPE PE-1080
1% Ampacet Process Aid Conc. 10919
Second Color Layer (0.6 mil)
2% Ampacet Black 190671A
25% Equistar EVA 242F
72% Huntsman MDPE PE-1080
1% Ampacet Process Aid Conc. 10919
Core (0.50 mil)
2% Ampacet Black 190671A
25% Equistar EVA 242F
72% Huntsman MDPE PE-1080
1% Ampacet Process Aid Conc. 10919
First Color Layer (0.6 mil)
20% Ampacet White 110868
25% AT Plastics EVA 1821
54% Huntsman MDPE PE-1080
1% Ampacet Process Aid Conc. 10919
Second Color Layer (0.6 mil)
2% Ampacet Black 190671A
25% Equistar EVA 242F
72% Huntsman MDPE PE-1080
1% Ampacet Process Aid Conc. 10919
First Skin Layer (0.25 mil-Transparent)
94% Surlyn 9120
5% Ampacet UV Concentrate 10561
1% Ampacet Process Aid Conc. 10919
Second Skin Layer (0.25 mil-transparent)
63% Huntsman MDPE PE-1080
35% Equistar EVA 242F
1% Ampacet UV Conc. 10561
1% Ampacet Process Aid Conc. 10919
Core
Base Layer (0.5 mil)
First Intermediate Layer (0.6 mil)
Second Intermediate Layer (0.6 mil)
45% Ampacet Cardinal Red 150623
28% Huntsman MDPE PE-1080
25% Equistar EVA 242F
1% Ampacet UV Conc. 10561
1% Ampacet Process Aid Conc. 10919
Second Color Layer (0.65 mil)
45% Ampacet Cardinal Red 150623
28% Huntsman MDPE PE-1080
25% Equistar EVA 242F
1% Ampacet UV Conc. 10561
1% Ampacet Process Aid Conc. 10919
Core (0.5 mil)
72% Huntsman MDPE PE-1080
25% Equistar EVA 242F
2% Ampacet Gray LR-89933
1% Ampacet Process Aid Conc. 10919
First Color Layer (0.4 mil)
45% Ampacet Cardinal Red 150623
28% Huntsman MDPE PE-1080
25% Equistar EVA 242F
1% Ampacet UV Conc. 10561
1% Ampacet Process Aid Conc. 10919
Second Color Layer (0.4 mil)
45% Ampacet Cardinal Red 150623
28% Huntsman MDPE PE-1080
25% Equistar EVA 242F
1% Ampacet UV Conc. 10561
1% Ampacet Process Aid Conc. 10919
First Skin Layer (0.25 mil-transparent)
94% Primacor 1420 Resin
5% Ampacet UV Conc. 10561
1% Ampacet Process Aid Conc. 10919
Second Skin Layer (0.25 mil-transparent)
63% Huntsman MDPE PE-1080
35% Equistar EVA 242F
1% Ampacet UV Conc. 10561
1% Ampacet Process Aid Conc. 10919
Core
Base Layer (0.5 mil)
First Intermediate Layer (0.6 mil)
Second Intermediate Layer (0.6 mil)
45% Ampacet Cardinal Red 150623
28% Huntsman MDPE PE-1080
25% Equistar EVA 242F
1% Ampacet UV Conc. 10561
1% Ampacet Process Aid Conc. 10919
Second Color Layer (0.4 mil)
45% Ampacet Cardinal Red 150623
28% Huntsman MDPE PE-1080
25% Equistar EVA 242F
1% Ampacet UV Conc. 10561
1% Ampacet Process Aid Conc. 10919
First Skin Layer (0.25 mil-transparent)
94% Primacor 1420 Resin
5% Ampacet UV Conc. 10561
1% Ampacet Process Aid Conc. 10919
Second Skin Layer (0.25 mil-Transparent)
63% Huntsman MDPE PE-1080
35% Equistar EVA 242F
1% Ampacet UV Conc. 10561
1% Ampacet MDPE PE-1080
Core (1.73 mils)
64% Huntsman PE-1080
18% Ampacet Gray Conc. LR 96896
17% Simulated Reground Trim Scrap
1% Ampacet Process Aid Conc. 10919
First Color Layer (0.53 mil)
40% AT Plastics EVA 1821
39% Huntsman PE-1821
20% Ampacet Spectra Red Conc. 150678
1% Ampacet Process aid Conc. 10919
Second Color Layer (0.53 mil)
40% AT Plastics EVA 1821
39% Huntsman PE-1821
20% Ampacet Spectra Red Conc. 150678
1% Ampacet Process aid Conc. 10919
First Skin Layer (0.11 mil-Transparent)
97% DuPont Surlyn 9120
2% Ampacet UV Conc. 10561
1% Ampacet Process Aid 10917
Second Skin Layer (0.11 mid-Transparent)
97% DuPont Surlyn 9120
2% Ampacet UV Conc. 10561
1% Ampacet Process Aid 10917
In one embodiment, the inventive multilayer film is provided as part of an adhesive composite where the film also comprises an adhesive layer adhered or attached to an outer surface of the film where the outer surface can in general be a skin layer. In another embodiment the above described adhesive composite also comprises a release liner adhered or attached to the adhesive layer. A release liner may comprise a backing liner and a layer of cured release coating layer adhered to the backing liner. The release coating is positioned between the adhesive and the backing liner. In an embodiment, the adhesive layer is positioned between a second skin layer of the multilayer thermoplastic film and a release liner or between a second skin layer and a release coating of a release liner. The adhesive layer is preferably adherent or attached to a skin layer comprising adhesive compatible polymers. A useful embodiment is depicted in
In one embodiment, the release liners utilized in the invention comprise a backing layer having a release coating on one surface thereof. A variety of release coatings are known in the art and these include silicone release coating compositions. The backing liner can comprise paper, a monolayered or multilayered polymeric film including a film which has been coextruded or coextruded and oriented, or combinations thereof. Examples of polymer films include polyolefin films, polyester films, and combinations thereof. Polycoated paper liners that have one side of the liner coated with a silicone release material also are useful. In one embodiment, the polycoating may comprise low density polyethylene, medium density polyethylene, ethylene propylene copolymer, propylene homopolymer, etc.
The present invention also comprises a method to vary the color of the outer surfaces of the inventive film as described throughout this application and as depicted in
Example 7 demonstrates the color variety and cost advantages of the method of the present invention to vary the color of the outer surfaces of the multilayer films.
Examples 7A-7F are six 5-layered inventive films which are prepared by coextrusion and have the following constructions:
(a) 1.7 mil opaque core containing 12-14% by wt. of progressively darker shades of gray opacifying concentrate (gray 1, 2, 4, 7, 9 and 10),
(b) 0.4 mil color layers containing 20% by wt. of a fire red pigment concentrate on both sides of the core, and
(c) 0.25 mil clear skin layers over the color layers.
Comparative Example 7 is a 3-layered comparative film which is prepared by coextrusion and has the following construction:
(a) 2.5 mil opaque core containing 32% by wt. of the fire red pigment concentrate used in the above 5-layered inventive films, and
(b) two 0.25 mil clear skin layers.
The Hunter Lab color values in Table 1 are measured for the six inventive films of Examples 7A-7F and comparative film Example 7, which used approximately fives times more of the fire red pigment concentrate than the inventive films, using a Hunter Lab MiniScan XEPlus Model No. 4500L unit according to ASTM Test Method E308. The Delta E values are calculated from the L, a and b values, and a Delta E value equal to or below about 2.3 is an indication of a color match between an inventive film and the comparative film. As can be seen from the result reported in Table 1, Example 7C provides a match for the film of comparative Example 7. The other Delta E values reported in Table 1 demonstrate that different shades of red can be obtained from a single red pigment concentrate in the films of the invention by varying the color, or shade of the core layer.
Each of the documents referred to in the Detailed Description section is incorporated herein by reference. All numerical quantities in this application used to describe or claim the invention are understood to be modified by the word “about” except in examples and where explicitly indicated otherwise. Range and ratio limits used to define the invention throughout this application, in both the specification and claims, are understood to be combinable.
While the invention has been explained in relation to specific embodiments, various modifications thereof will become apparent to those skilled in the art upon reading this application. It is understood that these various modifications, which fall within the scope of this detailed description and the appended claims, form a part of this invention.
This application claims the benefit of U.S. Provisional Application No. 60/631,314 filed Nov. 29, 2004, the contents of which are hereby incorporated by reference in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US05/42964 | 11/28/2005 | WO | 4/9/2007 |
| Number | Date | Country | |
|---|---|---|---|
| 60631314 | Nov 2004 | US |
