WO2021224870A1

WO2021224870A1 - Heat seal primer for flexographic plate mounting tape

Info

Publication number: WO2021224870A1
Application number: PCT/IB2021/053873
Authority: WO
Inventors: Scott A. Van Wert; Becky A. JETTO; Yu Yang; Chunjie Zhang
Original assignee: 3M Innovative Properties Company
Priority date: 2020-05-06
Filing date: 2021-05-06
Publication date: 2021-11-11

Abstract

Primer layers for adhesion of pressure sensitive adhesive materials to foam comprise a cured primer which is the reaction product of an epoxy resin and a polyamine and a thermoplastic polymer binder. The epoxy resin may be an aromatic epoxy resin. The polyamine may be a polymer such as polyethylenimine (PEI) or polyvinylamine (PVA). Three-layer constructions comprise the primer layer according to the present disclosure and a pressure sensitive adhesive layer, which may be directly bound to the primer layer, along with a release liner on the pressure sensitive adhesive face opposite the primer

Description

HEAT SEAL PRIMER FOR FLEXOGRAPHIC PLATE MOUNTING TAPE

Field of the Disclosure

This disclosure relates to primers for bonding a pressure sensitive adhesive (PSA) to a foam layer, such as may be used in a flexographic plate mounting tape, as well as flexographic plate mounting tapes incorporating this primer and methods of making and using such tapes.

Background of the Disclosure

Flexographic plate mounting tapes are used to mount flexographic printing plates to plate cylinders in a flexographic printing press. The following references may be relevant to the general field of technology of the present disclosure: JP 2004/285297, US 2003/0049415, US 2006/0145127, US 2011/0019280, US 2015/0361307, US 5,156,904, US 6,915,741, US 8,152,944, US 8,802,226, and US 8,962,777.

Summary of the Disclosure

Briefly, the present disclosure provides primer layers for adhesion of pressure sensitive adhesive materials to a foam layer, where the primer layer comprises epoxy resin, polyamine, and thermoplastic polymer binder. In some embodiments, the polyamine and epoxy resin together comprise a cured resin component. In some embodiments, the epoxy resin is an aromatic epoxy resin. In some embodiments, the polyamine is a polymer, such as polyethylenimine (PEI) or polyvinylamine (PVA). In some embodiments, the thermoplastic polymer binder is polyethylene vinylacetate copolymer (EVA). Additional embodiments of the primer layer of the present disclosure are described below under “Selected Embodiments.”

In another aspect, the present disclosure provides a three-layer construction comprising a first pressure sensitive adhesive layer detachably coupled to a release liner where the primer layer according to the present disclosure is directly bound to the pressure sensitive adhesive layer on the face opposite the release liner.

In various embodiments, the pressure sensitive adhesive material may comprise polyacrylate polymer. In various embodiments, the pressure sensitive adhesive material may comprise polyacrylate polymer comprising acidic polar monomer units. In various embodiments, the tape may comprise a second pressure sensitive adhesive layer coupled to the foam layer face opposite the first pressure sensitive adhesive layer. Additional embodiments of the three-layer constructions of the present disclosure are described below under “Selected Embodiments.”

In another aspect, the present disclosure provides tapes comprising the three-layer construction according to the present disclosure and a foam layer comprising a cellular or void structure, directly bound to the primer layer. In various embodiments, the foam layer may comprise one or more olefin polymers. In various embodiments one or both faces of the foam layer may comprise skin layer(s) of greater planar stiffness relative to the unskinned foam interior. In various embodiments one or both faces of the foam layer may optionally comprise a skin layer of greater density relative to the foam layer interior (skin layer with lower or essentially no void volume relative average foam interior void volume). In some embodiments, one or both skin layers may comprise an extensible polymer composition to allow the foam layer to bend around a 6 cm diameter cylinder without creasing or buckling. In some embodiments the skin layer may comprise an olefmic polymer including ethylene vinyl acetate, low and medium density polyethylene, linear low density polyethylene and the like. Additional embodiments of the three-layer constructions coupled to a foam layer tape of the present disclosure are described below under “Selected Embodiments.”

In another aspect, the present disclosure provides methods of making the three- layer constructions coupled to a foam layer tape according to the present disclosure comprising steps of: a) providing a PSA layer coated on an release liner; b) coating the PSA layer with a coating mixture comprising an epoxy resin, and a polyamine, and a heat sealable polymer; which may additionally comprise steps of c) reacting the curable aromatic epoxy resin with the polyamine to provide a primer layer comprising a cured primer; and d) laminating the primer layer to a foam layer at an elevated temperature to securely bond the prime to the foam. In some embodiments, steps a)-d) are carried out in the order a), b), c), d).

The preceding summary of the present disclosure is not intended to describe each embodiment of the present invention. The details of one or more embodiments of the invention are also set forth in the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims. In this application:

“directly bound” refers to two materials that are in direct contact with each other and bound together, with no intervening layers;

“(meth)acrylate” includes, separately and collectively, methacrylate and acrylate;

“pressure sensitive adhesive (PSA)” means materials having the following properties: a) tacky surface, b) the ability to adhere with no more than finger pressure, c) the ability to adhere without activation by any energy source, d) sufficient ability to hold onto the intended adherend, and e) sufficient cohesive strength to be removed cleanly from the adherend; which materials typically meet the Dahlquist criterion of having a storage modulus at 1 Hz and room temperature of less than 0.3MPa.

All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified.

As used in this specification and the appended claims, past tense verbs such as “coated” and “oriented” are intended to represent structure, and not to limit the process used to obtain the recited structure, unless otherwise specified.

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise.

As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

As used herein, “have”, “having”, “include”, “including”, “comprise”, “comprising” or the like are used in their open ended sense, and generally mean “including, but not limited to.” It will be understood that the terms “consisting of’ and “consisting essentially of’ are subsumed in the term “comprising,” and the like.

Brief Description of the Drawings

FIG. l is a cross-section of one embodiment of a flexographic plate mounting tape according to the present disclosure.

FIG. 2 is a cross-section of one embodiment of a flexographic plate mounting tape according to the present disclosure.

FIG. 3 is a cross-section of one embodiment of a flexographic plate mounting tape according to the present disclosure. Detailed Description

The present disclosure provides a primer for bonding pressure sensitive adhesive (PSA) to the foam substrate in a flexographic plate mounting tape. The present disclosure additionally provides flexographic plate mounting tapes incorporating this primer, and methods of making and using such tapes.

Flexographic plate mounting tapes are used to mount flexographic printing plates to plate cylinders in a flexographic printing press. Mounted flexographic printing plates may require washing between printing runs. The washing process may cause “nibs” of adhesive from the flexographic plate mounting tape to form. These small particles can compromise print quality by creating spots or flaws in the printed articles. Use of the primer according to the present disclosure provides reduced adhesive nib formation during in situ plate washing. Flexographic plate mounting tapes made with the subject primer demonstrate improved rub resistance, which results in reduced adhesive nib formation.

With reference to FIG. 1, one embodiment of flexographic plate mounting tape 110 according to the present disclosure provides a “three-layer” adhesive/primer/liner construction (primer layer 140, pressure sensitive adhesive layer 130, and release liner 135). Primer layer 140 is directly bound to pressure sensitive adhesive layer 130 and release liner 135 is releasably coupled to pressure sensitive adhesive layer 130 on the face opposite primer layer 140. Note that as used herein, layers may either be, in a first case, directly bound to each other, as that term is defined in the definitions section. In a second case, another term may be used, such as “coupled” or “adhered”. Terms used to describe the coupling or adherence of two layers that are other than “directly bound”, or where the language says “way be directly bound” are intended to be open ended and do not exclude the possibility of other, intervening layers - that is, they may be directly bound to each other or they may not be.

In some embodiments, a three-layer construction is provided in which primer layer 140 is directly bound (via a covalent bond) to pressure sensitive adhesive layer 130 with epoxy derived bonds.

In one embodiment, flexographic plate mounting tape 110 includes foam layer 120 and PSA layer 130 coupled to foam layer 120 through primer layer 140. In some embodiments, foam layer 120 is directly bound to primer layer 140, with no other intervening layers. In some embodiments, primer layer 140 is directly bound to PSA layer 130. In some embodiments, the major surface of the first PSA layer 130 that is opposite primer layer 140 may comprise a release liner 135. In some embodiments, foam layer 120 includes an optional skin layer (not shown) coupled to the foam layer and directly bound to primer layer 140.

With reference to FIG. 2, an embodiment of flexographic printing setup 200 is shown. It includes flexographic plate mounting tape 210 according to the present disclosure includes a foam layer 220, first PSA layer 230 coupled to foam layer 220 through a intervening first primer layer 240, and second PSA layer 250 coupled to the opposite face of foam layer 220 through a intervening second primer layer 260. In some embodiments, foam layer 220 is directly bound to first primer layer 240. In some embodiments, first primer layer 240 is directly bound to first PSA layer 230. In some embodiments, foam layer 220 is directly bound to second primer layer 260. In some embodiments, second primer layer 260 is directly bound to second PSA layer 250. In some embodiments, first PSA layer 230 and second PSA layer 250 have the same composition. In some embodiments, first PSA layer 230 and second PSA layer 250 differ in composition. In some embodiments, first primer layer 240 and second primer layer 260 have the same composition. In some embodiments, first primer layer 240 and second primer layer 260 differ in composition. In some embodiments, a release liner (not shown) is releasably coupled to one or both of the first PSA layer or the second PSA layer. Such optional release liners are removed before subsequent contact with either flexographic printing plate 295 or plate cylinder 290. In some applications flexographic plate mounting tape 210, flexographic printing plate 295 is attached to plate cylinder 290 of a flexographic printing press (not shown) by use of flexographic plate mounting tape 210. Typically, flexographic plate mounting tape 210 is coupled to flexographic printing plate 295 through first PSA layer 230 and coupled to plate cylinder 290 through second PSA layer 250. In some embodiments, foam layer 220 includes an optional skin layer (not shown) coupled to the foam layer and directly bound to first primer layer 240. In some embodiments, foam layer 220 includes optional skin layer (not shown) coupled to the foam layer and directly bound to second primer layer 260.

With reference to FIG. 3, a further embodiment of a flexographic printing setup 300 is shown. It includes flexographic plate mounting tape 310 comprising a first PSA layer 380 directly bound to first primer layer 375. In some embodiments, a first major surface of foam layer 370 is directly bound to first primer layer 375. In some embodiments, the opposing major surface of foam layer 370 is further coupled to internal adhesion layer 355, which is further coupled to carrier layer 320, which is further coupled to a second PSA layer 330. In some embodiments, first optional primer layer 360 is provided between carrier layer 320 and internal adhesion layer 355, In some embodiments, a second optional primer layer 340 is provided between carrier layer 320 and second PSA layer. First optional primer layer 360 and second optional primer layer 340 when present are not typically formulated to comprise a primer layer per in most embodiments described herein.

In some embodiments, first PSA layer 380 and second PSA layer 330 have the same composition. In some embodiments, first PSA layer 380 and second PSA layer 330 differ in composition. In some applications of flexographic plate mounting tape 310, flexographic printing plate 395 is adhesively coupled to plate cylinder 390 of a flexographic printing press (not shown) by use of flexographic plate mounting tape 310. Typically a flexographic plate mounting tape 310 is coupled to flexographic printing plate 395 through first PSA layer 380 and coupled to plate cylinder 390 through second adhesive layer 330.

With regard to embodiments associated with FIGS. 1-3, outer adhesive layers (such as PSA layer 130, first PSA layer 230, second PSA layer 250, first PSA layer 380, and second PSA layer 330) may comprise relief features in their outer surface (not shown). With regard to embodiments associated with FIGS. 2-3, outer adhesive layers (such as first PSA layer 230, second PSA layer 250, first PSA layer 380, and 2nd PSA layer330) may bear a release liner (not shown). In some such embodiments, the release liner has an embossed surface facing the adhesive layer which imparts and/or matches relief features in the outer surface of the PSA layer.

In some embodiments of the articles depicted in FIGS. 1-3, PSA layer 130, first PSA layer 230 and first PSA layer 380 have a thickness of at least 15 micrometers, in some embodiments at least 20 micrometers, and in some embodiments at least 30 micrometers. In some such embodiments those PSA layers have thickness of less than 200 micrometers, in some less than 100 micrometers, and in some less than 70 micrometers. In some embodiments, other adhesive layers are subject to the same constraints on thickness. In some embodiments of the articles depicted in FIGS. 1-3, primer layer 140, first primer layer 240, second primer layer 260 and first primer layer 375 have thickness of at least 1 micrometers, in some embodiments at least 3 micrometers, and in some embodiments at least 5 micrometers. In some such embodiments those primer layers have thickness of less than 8 micrometers, in some less than 12 micrometers, in some less than 25 micrometers and in some less than 50 micrometers.

In some embodiments of the article depicted in FIGS. 2-3, foam layer 220 and foam layer 370 have a thickness of at least 200 micrometers, in some embodiments at least 300 micrometers, and in some embodiments at least 400 micrometers. In some such embodiments foam layer 220 and foam layer 370 have a thickness of less than 2500 micrometers, in some less than 2000 micrometers, and in some less than 1500 micrometers.

In some embodiments, foam layer 220 and foam layer 370 include optional intervening skin layers (not shown, described in more detail below) directly bound to the foam layer and directly bound to adjacent first primer layer 240, second primer layer 260, and / or first primer layer 375.

In some embodiments, the primer comprises the reaction product of polyamine and curable epoxy resin comprising a cured polyamine resin component. In some embodiments, the primer comprises the reaction product of polyamine and curable epoxy resin comprising crosslinked polymer. In some embodiments, the crosslinked polymer comprises at least 3 wt% of the total weight of the primer layer, in some at least 5 wt%, in some at least 7 wt%, in some at least 9.5 wt%, in some at least 50 wt%, in some at least 60 wt%, in some at least 70 wt%, and in some at least 80 wt%. In some embodiments the polyamine includes primary, secondary, and tertiary amine groups. In some embodiments the polyamine is a polyethylenimine (PEI). In some embodiments the polyamine includes only primary amine groups and no secondary or tertiary amine groups. In some embodiments the polyamine is a polyvinylamine (PVA). In various embodiments the polyamine may be a high molecular weight polyamine, having a weight average molecular weight (Mw) of greater than 20,000 grams/mole, greater than 60,000 grams/mole, greater than 80,000 grams/mole, greater than 125,000 grams/mole, greater than 250,000 grams/mole, or in some embodiments greater than 600,000 grams/mole. In various embodiments the polyamine may be a low molecular weight polyamine, having a weight average molecular weight (Mw) of less than 20,000 grams/mole, less than 10,000 grams/mole, less than 2,000 grams/mole, less than 600 grams/mole, or in some embodiments less than 300 grams/mole. In some embodiments the curable epoxy resin is an aromatic curable epoxy resin. In particular, the use of an aromatic curable epoxy resin in a primer for application to a substrate comprising an aromatic polymer may provide enhanced adhesion.

A polyethylenimine (PEI) is a polymer comprising repeating units according to the formulas:

-CH2CH2-NH- or -CH2CH2-N-

The amine nitrogen may be secondary, in linear segments of the polymer, or may be tertiary, to form branch points. PEEs may include primary amine end groups. Linear PEEs contain all secondary amines, excluding primary amine end groups. Branched PEEs contain secondary and tertiary amine groups, as well as primary amine end groups.

Totally branched dendrimeric forms are also reported. PEEs are sometimes referred to as polyaziridine polymers, since they may be composed of monomer units derived from aziridine monomers.

In some embodiments, the primer layer additionally comprises thermoplastic polymeric binder. In some embodiments, the primer layer additionally comprises thermoplastic polymeric binder of ethylenic polymer. In some embodiments, the primer layer comprises thermoplastic polymeric binder of ethylene vinyl acetate copolymer. In some embodiments, the thermoplastic polymeric binder additionally comprises one or both of wax and resin. In some embodiments, the thermoplastic polymeric binder additionally comprises one or both of wax and resin comprising softening points below 150°C. In some embodiments, the thermoplastic polymeric binder components along with any additives such as waxes and resins are selected to provide hot adhesive tack of the primer layer within the range 80°C to 150°C. In some embodiments, the thermoplastic polymeric binders comprise at least 30 wt% of the total weight of the primer layer, in some at least 40 wt%, in some at least 50 wt%, in some at least 70 wt%, and in some at least 90 wt%. In some embodiments, the primer layer additionally comprises fillers. Any suitable fillers may be used, including silica particles such as fumed silica and the like.

In some embodiments, the present primer may be applied to a pressure sensitive adhesive coated on a release liner and stored for long periods before application to foam layers, rather than requiring prompt lamination of the primer to the foam layer. This characteristic allows greater flexibility in manufacture. Without wishing to be bound by theory, it is believed that this characteristic results from the condition that the reactive groups of the primer (such as epoxide functional groups) are involved in binding to the pressure sensitive adhesive, but are not involved in binding to the foam, while retaining the ability of the primer layer to be coupled to the foam when heated and passed through a lamination nip, and thus the epoxy reactive groups do not need to be kept “live” or “active” until lamination to the foam, yet an acceptable level of solvent resistance is realized once the pressure sensitive adhesive is coupled to the foam. Furthermore, in some embodiments of the present disclosure, the primed pressure sensitive adhesive and release liner roll may be stored for a long period and still be reliably laminated to a foam layer with heat and pressure.

The primer may be applied to the pressure sensitive adhesive on a release liner as, for example, as a mixture comprising an epoxy resin, and a polyamine, and a heat sealable polymer. The primer may be applied to the carrier as, for example, as a solution or suspension in aqueous solvent. The primer may be applied to the carrier by any suitable method, including spraying, coating, brushing, immersion, and the like. After application, the primer may be heated to first evaporate any solvent and then accelerate the crosslinking reaction between the polyamine and the curable epoxy resin.

Any suitable PSA layers may be used. In some embodiments, the PSA comprises a polyacrylate polymer. In some embodiments, the PSA comprises a tackified polyacrylate. In some embodiments, the PSA comprises a polyacrylate polymer comprising units derived from polar monomer in an amount of 0.1-15.0 wt% of the total weight of the polyacrylate polymer, in some embodiments 0.5-15.0 wt%, and in some embodiments 3.0-12.0 wt% wherein the polar monomer is selected from the group consisting of acrylic acid, itaconic acid, N,N dimethylacrylamide, N-vinyl-2-pyrrolidone, N-vinyl caprolactam, acrylonitrile, tetra-hydrofurfuryl acrylate, glycidyl acrylate, 2- phenoxyethylacrylate, benzylacrylate, and combinations thereof. In some embodiments, the PSA comprises a polyacrylate polymer comprising units derived from carboxylic acid functional monomer in an amount of 0.1-15.0 wt% of the total weight of the polyacrylate polymer, in some embodiments 0.5-15.0 wt%, and in some embodiments 3.0-12.0 wt%.

In some embodiments, the PSA comprises a polyacrylate polymer comprising units derived from acrylic acid monomer in an amount of 0.1-15.0 wt% of the total weight of the polyacrylate polymer, in some embodiments 0.5-15.0 wt%, and in some embodiments 3.0-12.0 wt%. In some embodiments, the PSA comprises a tackified rubber. In some embodiments, the PSA comprises a tackified natural rubber. In some embodiments, the PSA comprises a tackified synthetic rubber. In some embodiments comprising multiple PSA layers, all PSA layers are of the same composition. In some embodiments comprising multiple PSA layers, PSA layers differ in composition. In various embodiments, PSA layers, comprise cross-linked polymers.

In some embodiments, the subject primer present in the three-layer construction described above with reference to FIG. 1 is laminated to a foam layer with heat and pressure. The material of the foam layer is typically resilient and possesses rapid rebound and low compression set characteristics and may be crosslinked. In some embodiments, the foam layer may comprise any suitable polymeric material. In some embodiments, the foam layer comprises an olefmic polymer. In some embodiments, the foam layer comprises ethylenic polymer, wherein the ethylenic polymer may include polyethylene, ethylene/vinyl acetate (EVA) copolymer, ethylene acrylic acid copolymer, ethylene methyl acrylate copolymer, and ethylene propylene copolymer and combinations thereof. In some embodiments, the foam layer comprises ethylene/vinyl acetate (EVA) copolymer. In some embodiments, the foam layer comprises crosslinked ethylene/vinyl acetate (EVA) copolymer. In some embodiments, the foam layer comprises one or more polymers comprising a thermoplastic elastomer, block isoprene copolymer, a thermoplastic elastomer block butadiene copolymer, a poly(meth)acrylate polymer, a polyurethane polymer, a olefin polymer, a ethylenic polymer, a polypropylene polymer; a polyester polymer, or a polycarbonate polymer. Foam layers may be foamed by use of chemical blowing agents, such as inert gasses, air, or chemical species that break down to release gasses upon heating; or physical blowing agents, such as expandable microspheres.

In various embodiments one or both faces of the foam layer may comprise skin layer(s) of greater planar stiffness relative to that of an unskinned foam interior. In some embodiments the foam layer may comprise on one (or both) faces’ skin layer(s) with lower (or in some cases, essentially no) void volume relative to the average foam interior void volume. In some embodiments, one or both skin layers may comprise a polymer composition providing an elastically extensible skin layer. In various embodiments, the foam layer with any optional skin layers comprises flexible materials selected to the provide a layer that may be wrapped around a 100 centimeter diameter cylinder without layer creasing or buckling when each face is in-turn orientated to the surface of the cylinder. In some embodiments, a less extensible, greater stiffness elastic skin layer is provided on one foam face, with an optional lower stiffness extensible skin layer on the opposite face, where layer compositions are selected to provide an entire foam layer that may be wrapped around a 10 centimeter diameter cylinder without causing creasing or buckling when the non-extensible skin layer face is orientated away from the surface of the cylinder.

In some embodiments the skin layer may comprise an olefmic polymer including ethylene vinyl acetate, low and medium density polyethylene, linear low density polyethylene and the like.

Flexographic printing plates may be of any suitable material. In some embodiments, flexographic printing plates comprise polymeric materials, which in some embodiments are one or more polyesters.

Flexographic printing press plate cylinders may be of any suitable material. In some embodiments, flexographic printing press plate cylinders comprise polymeric materials, which in some embodiments are one or more polyurethanes. In some embodiments, flexographic printing press plate cylinders comprise metal materials, which in some embodiments are steel.

Additional embodiments are recited in the Selected Embodiments and Examples below.

Selected Embodiments

The following embodiments, designated by letter and number, are intended to further illustrate the present disclosure but should not be construed to unduly limit this disclosure. PI . A primer layer for adhesion of a pressure sensitive adhesive material to a foam layer, the primer layer comprising thermoplastic polymer binder, polyamine and epoxy resin.

P2. A primer layer according to PI wherein the polyamine and epoxy resin together comprise a cured resin component.

P3. A primer layer for adhesion of a pressure sensitive adhesive material to a foam, the primer layer comprising a thermoplastic polymer binder and a cured resin component comprising the reaction product of epoxy resin and polyamine.

P3. The primer layer according to P1-P2 wherein the cured primer component comprises no greater than 50 wt% of the total weight of the primer layer.

P4. The primer layer according to P1-P2 wherein the cured primer component comprises no greater than 30 wt% of the total weight of the primer layer.

P5. The primer layer according to P1-P2 wherein the cured primer component comprises no greater than 15 wt% of the total weight of the primer layer.

P6. The primer layer according to any of the preceding embodiments wherein the epoxy resin is an aromatic epoxy resin.

P7. The primer layer according to any of the preceding embodiments wherein the poly amine is a polymer.

P8. The primer layer according to any of the preceding embodiments wherein the polyamine is a polyethylenimine (PEI).

P9. The primer layer according to any of the preceding embodiments wherein the polyamine is a polyvinylamine (PVA). P10. The primer layer according to any of the preceding embodiments wherein the polyamine has a molecular weight greater than 600,000 grams/mole.

PI 1. The primer layer according to any of the preceding embodiments wherein the thermoplastic polymeric binder comprises ethylenic polymer.

P12. The primer layer according to any of the preceding embodiments wherein the thermoplastic polymeric binder comprises ethylene/vinyl acetate copolymer (EVA).

P13. The primer layer according to any of the preceding embodiments wherein the thermoplastic polymeric binder additionally comprises one or both of wax and resin.

P14. The primer layer according to P13 wherein the thermoplastic polymeric binder comprises ethylene/vinyl acetate copolymer (EVA), wax and resin components selected to provide the primer layer within tackiness when heated to 80°C to 150°C.

PI 5. The primer layer according to any of the preceding embodiments wherein the thermoplastic polymeric binder comprises at least 50 wt% of the total weight of the primer layer.

PI 6. The primer layer according to any of the preceding embodiments wherein the thermoplastic polymeric binder comprises at least 70 wt% of the total weight of the primer layer.

PI 7. The primer layer according to any of the preceding embodiments wherein the thermoplastic polymeric binder comprises at least 85 wt% of the total weight of the primer layer.

PI 8. The primer layer according to any of the preceding embodiments additionally comprising 0.1-20.0 wt% inorganic filler.

PI 9. The primer layer according to any of the preceding embodiments additionally comprising essentially no inorganic filler. TL1. A three4ayer construction comprising the primer layer according to any of the preceding embodiments directly bound to a first major surface of a pressure sensitive adhesive layer, and a release liner layer directly bound to a second surface of the pressure sensitive adhesive layer that is opposite the primer layer.

TL2. The three-layer construction according to embodiment TL1 wherein the primer layer is covalently bound to the pressure sensitive adhesive layer with epoxy derived bonds.

TL3. The three-layer construction according to any of embodiments TL1-TL2 wherein the pressure sensitive adhesive layer comprises polyacrylate polymer.

TL4. The three-layer construction according to any of embodiments TL1-TL2 wherein the pressure sensitive adhesive layer comprises a polyacrylate polymer comprising units derived from polar monomer in an amount of 0.1-15.0 wt% wherein the polar monomer is selected from the group consisting of acrylic acid, itaconic acid, N,N dimethylacrylamide, N-vinyl-2-pyrrolidone, N-vinyl caprolactam, acrylonitrile, tetra-hydrofurfuryl acrylate, glycidyl acrylate, 2-phenoxyethylacrylate, benzyl acrylate, and combinations thereof.

TL5. The three-layer construction according to any of embodiments TL1-TL2 wherein the pressure sensitive adhesive layer comprises a polyacrylate polymer comprising units derived from acrylic acid monomer in an amount of 0.1-15.0 wt% of the total weight of the polyacrylate polymer.

R1. A roll of the three-layer construction according to any of embodiments TL1-TL5 rolled upon itself.

TP1. A tape comprising a first three-layer construction according to any of embodiments TL1-TL5 and a foam layer.

TP2. The tape according to TP1 wherein the foam layer is directly bound to the primer layer of a first three-layer construction. TP3. The tape according to any of embodiments TP1-TP2 wherein the foam layer comprises one or more polymers comprising a thermoplastic elastomer block isoprene copolymer, a thermoplastic elastomer block butadiene copolymer, a poly(meth)acrylate polymer, a polyurethane polymer, a olefin polymer, a ethylenic polymer, a polypropylene polymer; a polyester polymer, or a polycarbonate polymer.

TP4. The tape according to any of embodiments TP1-TP2 wherein the foam layer comprises one or more olefin polymers.

TP5. The tape according to any of embodiments TP1-TP2 wherein the foam layer comprises one or more ethylenic polymers.

TP6. The tape according to any of embodiments TP1-TP2 wherein the foam layer comprises ethylenic polymer, wherein the ethylenic polymer is selected from the group consisting of polyethylene, ethylene/vinyl acetate (EVA) copolymer, ethylene acrylic acid copolymer, ethylene methyl acrylate copolymer, and ethylene propylene copolymer and combinations thereof.

TP7. The tape according to any of embodiments TP1-TP2 wherein the foam layer comprises ethylene/vinyl acetate (EVA) copolymer.

TP8. The tape according to any of embodiments TP1-TP6 wherein the foam layer comprises skin layer(s) on one or both faces.

DC1. The tape according to any of embodiments TP1-TP8 additionally comprising a second pressure sensitive adhesive layer to provide a double sided PSA foam tape.

DC2. The tape according to embodiment DC1 wherein second pressure sensitive adhesive layer is an outermost layer of the tape. DC3. The tape according to any of embodiments TP1-TP8 additionally comprising a second three-layer construction according to any of embodiments TL1-TL5 directly bound to foam layer side opposite the first three-layer construction.

DC4. The tape according to embodiment DC1 wherein the pressure sensitive adhesive layer of the second three-layer construction is an outermost layer of the tape.

DC5. The tape according to any of the embodiments DC1 to DC4 which is a flexographic plate mounting tape for adhering a flexographic printing plate to a plate cylinder in a flexographic printing press.

Ul. The use of the tape according to any of embodiments TP1-TP8 or DC1-DC5 to adhere a flexographic printing plate to a plate cylinder of a flexographic printing press.

TM1 . A method of making a three-layer construction according to any of embodiments TP1-TP8 comprising the steps of: a) providing a pressure sensitive adhesive layer on a release liner; and b) coating the pressure sensitive adhesive layer with a coating mixture comprising thermoplastic polymer binder, polyamine and epoxy resin. c) reacting the epoxy resin with the polyamine to form a cured primer.

TM2. The method according to TM1 additionally comprising the step of: d) laminating the primer to a foam layer under heat and pressure.

TM3. The method according to TM2 additionally comprising the steps of: e) laminating a second three-layer construction according to any of embodiments TL1-TL5 under heat and pressure to the foam layer. f) removing the release liner from either the first or second three-layer construction g) winding the resulting tape in a roll form. MU 1. A method of mounting flexographic printing plates to plate cylinders in a flexographic printing press comprising the steps of: a) providing a segment of tape according to any of embodiments TP1-TP8 or DC1-DC5; b) adhering the segment of tape to a flexographic printing plate; c) adhering the flexographic printing plate to a plate cylinder of a flexographic printing press by adhering the segment of tape to the plate cylinder.

MU2. A method of mounting flexographic printing plates to plate cylinders in a flexographic printing press comprising the steps of: a) providing a segment of tape according to any of embodiments TP1-TP8 or DC1-DC5; b) adhering the segment of tape to a plate cylinder of a flexographic printing press; c) adhering the flexographic printing plate to the plate cylinder by adhering the segment of tape to the flexographic printing plate.

Objects and advantages of this disclosure are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

Examples

Unless otherwise noted, all reagents were obtained or are available from Aldrich Chemical Co., Milwaukee, WI, or may be synthesized by known methods.

Materials

Test Methods

Rub Resistance 1

Rub resistance was tested per ASTM D7835/D7835M - 13: “Standard Test Method for Determining the Solvent Resistance of an Organic Coating using a Mechanical Rubbing Machine” with the following modifications. The mechanical finger, exerting a load of 900 grams and a stroke length of two inches (5.1 centimeters), was covered with four layers of dry cheese cloth.

The test specimens were prepared as follows. Samples of double sided pressure sensitive adhesive tape constructions, measuring 1 inch wide by 5 inches long (2.54 centimeters by 12.7 centimeters) were adhered to a stainless steel plate measuring 2 inches wide by 6 inches long (5.1 centimeters by 15.2 centimeters), by removing the release liner from the supplementary adhesive face, and adhering the specimen to the panel, and then removing the primary release liner. A solvent combination of 90: 10 (w:w) / N-propanol:N- propyl acetate was then dripped onto the exposed adhesive surface in such a manner as to completely cover the adhesive surface area to be tested.

The adhesive surface with solvent thereon was then covered with a microscope slide to prevent solvent evaporation. After one minute, the slide was removed and the adhesive surface was blotted dry using a tissue to remove any remaining solvent. The test specimen panel was then held fast to the rubbing machine platform and immediately evaluated for its rub resistance using 25 double rubs of the mechanical finger. One rub consisted of one complete forward and backward motion over the exposed solvent soaked adhesive surface.

The rubbed sample was then visually evaluated for adhesive removal. The sample was rated as “pass” if the size of the area of completely exposed primer as evidenced by a shiny, non-sticky region is 50% or less of the total solvent soaked and rubbed area. The sample was rated as “fail” either if the size of the area of completely exposed primer as evidenced by a shiny, non-sticky region was more than 5% of the total solvent soaked and rubbed area or if adhesive nibs were observed on the adhesive or finger surfaces. One test specimen was evaluated for each Example and Comparative Example.

Preparation of Primer Solution

Primer solution 1 A was prepared by mixing the components and amounts shown in Table 1 in a glass four-ounce jar in the following order using a magnetic mixer and stir bar at a moderate rate: First deionized water was added to the jar followed by Epoxy with mixing for one minute. Next, PEI was added and mixed for one minute followed by addition of Thermoplastic Polymer Dispersion and mixing for one minute (at 25% solids).

Table 1: Primer Solutions

*Weight of material as

i.e., at the stated dilution or solids content.

Preparation of Pressure Sensitive Adhesive Transfer Tape

An adhesive precursor syrup was prepared by mixing 90 parts by weight (pbw) IOA, 10 pbw AA, and 0.04 pbw Photoinitiator and partially polymerizing it under a nitrogen atmosphere by exposure to an ultraviolet radiation source having a spectral output from 300-400 nanometers with a maximum at 351 nanometers to provide a syrup having a viscosity of about 3 Pa*s (3000 centipoise) and a monomer conversion of about 8%. Next, 0.12 parts of Triazine, 0.375 parts of HDD A, and an additional 0.12 parts of Photoinitator were added to the syrup and fully dissolved to give the final coatable adhesive precursor syrup. This syrup was then knife coated onto the embossed side of a release liner and exposed to ultraviolet radiation by means of a series of lamps having a spectral output from 300-400 nanometers with at maximum at 351 nanometers in a nitrogen-rich atmosphere for a time of 105 seconds to provide a total dose of 510 milliJoules/square centimeter as measured using a calibrated NIST radiometer. An adhesive transfer tape having pressure sensitive adhesive (PSA) layer, approximately 0.002 inches (51 micrometers) thick, on the embossed surface of the release liner was thereby obtained. The adhesive transfer tape was stored at ambient conditions prior to use.

Preparation of Primed Pressure Sensitive Adhesive Transfer Tape

A wet layer of primer solution 4A was applied to adhesive transfer tape 2C using a #18 wire round Mayer rod. The primer coating was dried and cured in a forced air convection oven for 120 seconds at 71°C resulting in dried prime layer coverage of 8.5 g/sq m.

Preparation of Primed Pressure Sensitive Adhesive Transfer Tape

The same procedure to prepare primed pressure sensitive adhesive transfer tape IE was used to prepare Comparative Example IE, except that the primer solution coated was unaltered Thermoplastic Polymer Dispersion.

Preparation of Adhesive Bonded Foam Laminates

Examples ID and Comparative Examples ID

The Example 1C and Comparative Example 1C primed adhesive transfer tapes were laminated to a foam layer, by passing both through a heated rolling nip so that the interface between the foam and primer were bonded by maintaining a temperature between 126°C and 131°C for greater than two 2 seconds through a heated rolling nip. Using the same heated nip process, a supplemental primed adhesive transfer tape was bonded to the opposite foam face. The supplemental primed adhesive transfer tape thereby provided a means for bonding the adhesive bonded foam laminates to the stainless steel panel in order to complete Rub Resistance Test 2 on each example. The rub resistance test 2 result for Example ID was “Pass” and for Comparative Example ID was “Fail”.

Various modifications and alterations of this disclosure will become apparent to those skilled in the art without departing from the scope and principles of this disclosure, and it should be understood that this disclosure is not to be unduly limited to the illustrative embodiments set forth hereinabove.

Claims

We claim:

1. A primer layer for adhesion of a pressure sensitive adhesive material to a foam layer, the primer layer comprising a thermoplastic polymer binder, a polyamine, and an epoxy resin.

2. The primer layer according to claim 1. wherein the polyamine and the epoxy resin together comprise a cured resin component.

3. The primer layer according to any of the preceding claims wherein the epoxy resin is an aromatic epoxy resin.

4. The primer layer according to any of the preceding claims wherein the polyamine is a polyethylenimine (PEI).

5. The primer layer according to any of the preceding claims wherein the polyamine is a polyvinylamine (PVA).

6. The primer layer according to any of the preceding claims wherein the thermoplastic polymeric binder comprises ethylenic polymer.

7. The primer layer according to any of the preceding claims wherein the thermoplastic polymer resin comprises ethylene vinyl acetate copolymer.

8. The primer layer according to any of the preceding claims wherein the thermoplastic polymeric binder additionally comprises one or both of wax and resin.

10. The primer layer according to any of the preceding claims wherein the thermoplastic polymeric binder comprises polymeric binder, and wax and resin components selected to provide a hot tack of the primer layer within the range 80°C to 150°C.

11. The primer layer according to any of the preceding claims wherein the thermoplastic polymeric binder comprises at least 50% by weight of the total mass composition of the primer layer.

12. The primer layer according to any of the preceding claims wherein the thermoplastic polymeric binder comprises at least 70% by weight of the total mass composition of the primer layer.

13. A three-layer construction comprising the primer layer according to any of the preceding claims directly bound to a first major surface of a pressure sensitive adhesive layer, and a release liner layer directly bound to a second surface of the pressure sensitive adhesive layer that is opposite the primer layer.

14. The three-layer construction according to claim 13 wherein the primer layer is covalently bound to the pressure sensitive adhesive layer with epoxy derived bonds.

15. The three-layer construction according to any of claims 13-14 wherein the pressure sensitive adhesive layer comprises a polyacrylate polymer.

16. The three-layer construction according to claim 15 wherein the first pressure sensitive adhesive layer comprises monomer units derived from acrylic acid in an amount of 0.1-15.0 wt% of the total weight of the polyacrylate polymer

17. A tape comprising the three-layer construction according to any of claims 13-16 and a foam layer coupled to a major side of the primer layer that is opposite the major side that interfaces with the pressure sensitive adhesive layer.

18. The foam tape of claim 17, wherein coupled to comprises directly bound.

19. A tape according to claim 17 or 18 wherein the foam layer comprises ethylenic polymer, wherein the ethylenic polymer is selected from the group consisting of polyethylene, ethylene/vinyl acetate (EVA) copolymer, ethylene acrylic acid copolymer, ethylene methyl acrylate copolymer, and ethylene propylene copolymer and combinations thereof.

20. A tape according to claim 17 or 18 wherein the foam layer comprises polyethylene vinyl acetate copolymer (EVA).

21. A tape according to any of claims 17-20 wherein the foam layer further comprises skin layer(s) on one or both faces.

22. The tape according to any of claims 17-21 additionally comprising a second pressure sensitive adhesive layer residing on the tape face opposite the pressure sensitive adhesive layer of the three-layer construction.

23. The tape according to any of claims 17-22 additionally comprising a second three- layer construction according to claims 13-16 coupled to the tape face opposite the pressure sensitive adhesive layer of the three-layer construction.

24. A method of making a three-layer construction according to any of claims 13-16 comprising the steps of: a) providing a pressure sensitive adhesive layer on a release liner; b) coating the pressure sensitive adhesive layer with a coating mixture comprising thermoplastic polymer binder, polyamine and epoxy resin; and, c) reacting the epoxy resin with the polyamine to form a cured primer.

25. The method according to claim 24 additionally comprising the step of: d) laminating the primer to a foam layer under heat and pressure.

26. The method according to claim 25 additionally comprising the steps of: e) laminating a second three-layer construction according to any of claims 13- 16 under heat and pressure to the foam layer; f) removing the release liner from either the first or second three-layer construction; and, g) winding the resulting tape in a roll form.