UV curable adhesives and related methods

Abstract

Pressure sensitive adhesives that include architectured polymers are described. Also described are methods for producing the noted polymers and pressure sensitive adhesives. In addition, articles including the pressure sensitive adhesives are described.

Description

UV CURABLE ADHESIVES AND RELATED METHODSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Number 63 / 560,171 filed on March 1, 2024, which is incorporated herein in its entirety.TECHNICAL FIELD

[0002] The present subject matter relates to methods of preparing architecture polymers, and pressure-sensitive adhesives, including such polymers. The present subject matter also relates to the pressure-sensitive adhesives formed from the methods. Additionally, the present subject matter relates to articles including the pressure sensitive adhesives.BACKGROUND

[0003] Acrylic, pressure-sensitive adhesives (PSAs) are used for high-performance applications because of their excellent balance of peel adhesion and cohesive strength. In many cases, acrylic-based PSAs are used for high-temperature applications. However, a disadvantage associated with conventional acrylic-based adhesives is that they are typically characterized by either ultra violet (UV) curability or high temperature resistance. This is disadvantageous in applications where it is desired to apply the PSA and then cure it via UV curing, as well as subject the PSA to high temperatures during application and / or use.

[0004] Accordingly, a need exists for acrylic based polymers that are both UV curable and high temperature resistant. A need further exists for such polymers that can be tuned for use in different applications, and that can be coated and crosslinked at high speeds to form PSAs. Additionally, a need exists for such polymers that have a reduced sensitivity to cross-contamination and exposure to environmental conditions, such as moisture. An additional need is such polymers that have a high solids content.SUMMARY

[0005] The difficulties and drawbacks associated with previous approaches are addressed in the present subject matter as follows.

[0006] A first aspect of the present disclosure provides an adhesive composition comprising the crosslinkable reaction product of a mixture comprising: 20 to 50 wt% of a multifunctional aliphatic urethane acrylate, wherein the multifunctional aliphatic urethane acrylate comprises 2 to 3 functional groups, 3 to 40 wt% of a monofunctional aliphatic urethane acrylate, 5 tomultifunctional acrylate.

[0007] Another aspect of the present disclosure provides a method of making the adhesive composition according to the first aspect, comprising the steps of providing a crosslinkable mixture comprising: 20 to 50 wt% of a multifunctional aliphatic urethane acrylate, wherein the multifunctional aliphatic urethane acrylate comprises 2 to 3 functional groups; 3 to 40 wt% of a monofunctional aliphatic urethane acrylate; 5 to 15 wt% of a UV reactive adhesion promoter; 5 to 20 wt% of a multifunctional thiol; and 3 to 15% of a multifunctional acrylate; mixing the crosslinkable mixture; and exposing the crosslinkable mixture to UV radiation, thereby forming the reaction product of the crosslinkable mixture

[0008] A further aspect of the present disclosure provides an article comprising the adhesive composition of the first aspect.

[0009] The compositions and methods described herein overcome the limitations of current commercial products by creating controlled architecture polymers that are high temperature resistant and UV curable, and that can be tuned for use in different applications.DETAILED DESCRIPTIONI. Definitions

[0010] The accompanying drawings are representative of some, but not all embodiments described herein. The claims should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0011] As used in the specification, and in the appended claims, the singular forms "a", "an", "the", include plural referents unless the context clearly dictates otherwise.

[0012] As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably. Thus, for example, a composition that comprises "an" additive can be interpreted to mean that the composition includes "one or more" additives.

[0013] The terms "preferred" and "preferably" refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

[0014] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). Furthermore, disclosure of a range includes disclosure of all subranges included within the broader range (e.g., 1 to 5 discloses 1 to 4, 1.5 to 4.5, and 1 to 2).

[0015] Except as otherwise indicated, the term "weight percent" or "wt%" refers to the concentration of a component or composition based on the total weight of the composition, expressed as a percentage.

[0016] Except as otherwise indicated, the term "parts by weight" refers to the concentration of a component or composition based on the total weight of the composition.

[0017] As used herein, the terms "comprise(s)," "include(s)," "having," "has," "contain(s)," and variants thereof, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structure.

[0018] The term "component" refers to any part of a composition, polymer or coating that includes a particular feature or structure. Examples of components include compounds, monomers, oligomers, polymers, and organic groups contained there.

[0019] As used herein the term "aliphatic" is defined as including alkyl, alkenyl, alkynyl, halogenated alkyl, and cycloalkyl groups as described above. A "lower aliphatic" group is a branched or unbranched aliphatic group having from 1 to 10 carbon atoms.

[0020] As used herein the term "alkyl" refers to a branched or unbranched saturated hydrocarbon group of 1 to 24 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, hexyl, heptyl, octyl, decyl, tetradecyl, hexadecyl, eicosyl, tetracosyl, and the like. As used herein a "lower alkyl" group is a saturated branched or unbranched hydrocarbon having from 1 to 10 carbon atoms. In some embodiments, alkyl groups have 1 to 4 carbon atoms may be used. Alkyl groups may be "substituted alkyls" wherein one or more hydrogen atoms are substituted with a substituent such as halogen, cycloalkyl, alkoxy, amino, hydroxyl, aryl, or carboxyl.

[0021] As used herein the term "aryl" refers to any carbon-based aromatic group including, but not limited to, phenyl, naphthyl, and other suitable aryl compounds. As used herein the term "aryl" also includes "heteroaryl group," which is defined as an aromatic group that has at least one heteroatom incorporated within the ring of the aromatic group. Examples of heteroatoms include,but are not limited to, nitrogen, oxygen, sulfur, and phosphorus. The aryl group may be substituted with one or more groups including, but not limited to, alkyl, alkynyl, alkenyl, aryl, halide, nitro, amino, ester, ketone, aldehyde, hydroxy, carboxylic acid, or alkoxy, or the aryl group may be unsubstituted.

[0022] As used herein the term "cycloalkyl" refers to a non-aromatic carbon-based ring composed of at least three carbon atoms. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. As used herein the term "heterocycloalkyl group" is a cycloalkyl group as defined above in which at least one of the carbon atoms of the ring is substituted with a heteroatom such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorous.

[0023] As used herein the term "oligomer" refers to a molecule that has an average molecular weight (Mw) within a range of from about 300 to about 40,000 g / mol.

[0024] The term "syrup" refers to a composition having a viscosity of from about 10 to about 10,000 cPs at room temperature. As used herein, the terms "room temperature" or "ambient temperature" are used interchangeably and refer to temperatures within the range of from about 15° to about 25°C, more typically about 22° C. (72° F.).

[0025] The term "(meth)acrylate" used herein, refers to acrylate and / or methacrylate monomers or polymers.

[0026] As used herein, the term "multifunctional" means including more than one functional group.

[0027] As used herein, the term "monofunctional" means including one functional group.

[0028] As used herein, the term "polymer" may refer to a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The generic term "polymer" embraces the terms "homopolymer," "copolymer", and the like.

[0029] As used herein, the term "derived from" or "prepared by the reaction of" or "reaction product of" refers to the polymerization of monomers to form the product being referred to. That is, upon polymerization, the monomer, as present in the polymer, is chemically different from the unreacted monomer.

[0030] As used herein, the term "cure" refers to polymerization and / or crosslinking.

[0031] As used herein, the term "100% solids" means a composition containing no non- reactive carrier, such as for example water or solvents, that could evaporate while curing. Suchcompositions maintain 100% of their body and shape after curing. Accordingly, the wet film thickness of a 100% solids composition (thickness of the composition when applied wet), will be equal or substantially equal to the dry film thickness of the composition (thickness of the composition when cured and dry).

[0032] As used herein, the term "adhesion promoter" means a substance or chemical compound that is used to enhance the bonding between two surfaces. It works by providing a reactive surface for the adhesive material to attach to, thereby increasing the strength and durability of the bond.

[0033] As used here, the term "architecture polymer", "architectured polymer" or "polymer architecture" in polymer science relates to polymers that are intentionally designed to exhibit characteristics that deviate from a strictly linear polymer chain.II. Crosslinkable Reaction Product

[0034] Generally, the present subject matter provides a pressure sensitive adhesive composition that is UV curable and that has high heat resistance. The adhesive composition can be applied at ambient or elevated temperatures.

[0035] The pressure sensitive adhesive composition comprises the crosslinkable reaction product of a mixture comprising: 20 to 50 wt% of a multifunctional aliphatic urethane acrylate, wherein the multifunctional aliphatic urethane acrylate comprises 2 to 3 functional groups; 20 to 40 wt% of a monofunctional aliphatic urethane acrylate; 5 to 15 wt% of a UV reactive adhesion promoter; 5 to 20 wt% of a multifunctional thiol; and 3 to 15% of a multifunctional acrylate.

[0036] The pressure sensitive adhesive composition includes at least one multifunctional aliphatic urethane acrylate. The multifunctional aliphatic urethane acrylate forms the polymer backbone of the PSA. In some embodiments, the multifunctional aliphatic urethane acrylate includes 2 to 3 functional groups. In some embodiments, the multifunctional aliphatic urethane acrylate includes 2 functional groups. In some embodiments, the multifunctional aliphatic urethane acrylate includes 3 functional groups. In some embodiments, the multifunctional aliphatic urethane acrylate is present in an amount of from 20 to 50 wt%, based on the total weight of the adhesive composition. In some embodiments, the multifunctional aliphatic urethane acrylate is present in an amount of from 20 to 45 wt%, 20 to 40 wt%; from 20 to 35 wt%, from 20 to 30 wt%, from 25 to 50 wt%, from 30 to 50 wt%, from 35 to 50 wt%, from 40 to 50 wt%, from 35 to 45 wt%, or from 30 to 40 wt%, based on thetotal weight of the adhesive composition. In some embodiments, the multifunctional aliphatic urethane acrylate is an oligomer. In some embodiments, the multifunctional aliphatic urethane acrylate has a viscosity of from 2000 to 20000 mPa.s; from 2000 to 4000 mPa.s, from 2000 to 5000 mPa.s, from 3000 to 5000 mPa.s, from 4000 to 6000 mPa.s, from 5000 to 10000 mPa.s, from 5000 to 15000 mPa.s, or from 8000 to 20000 mPa.s, at 60 °C. In some embodiments, the multifunctional aliphatic urethane acrylate has viscosity of from 25000 to 65000 mPa.s; from 30000 to 60000 mPa.s, or from 35000 to 55000 mPa.s, at 60 °C. at 60 °C In some embodiments, the multifunctional aliphatic urethane acrylate has viscosity of from 2000 to 65000 mPa.s; from 3000 to 60000 mPa.s, from 4000 to 55000 mPa.s, or from 8000 to 50000 mPa.s, at 60 °C. In some embodiments, the multifunctional aliphatic urethane acrylate has a glass transition temperature (Tg) of from -80 to 0 °C. Accordingly, the multifunctional aliphatic urethane acrylate has a low Tg. The use of a high Tg multifunctional aliphatic urethane acrylate would disadvantageously not provide an adhesive that is pressure sensitive. Examples of commercially available lowTg multifunctional aliphatic urethane acrylates include but are not limited to SHIKOH™ UV-3000B, SHIKOH™ UV-3300B, and SHIKOH™ UV-3700B (commercially available from Mitsubishi Chemical Corporation located in Japan); Photomer 6010, Photomer 6630, Photomer 6643, Photomer 6644 and Photomer 6645 from IGM Resins; Ebecryl’ 230, Ebecryl’ 270 and Ebecryl’ 8411 (commercially available from Allnex located in Germany).

[0037] The composition includes at least one monofunctional aliphatic urethane acrylate. The end use, and application method of the PSA will generally be determined by the viscosity of the adhesive. The adhesive viscosity can be adjusted by adjusting the amount of the monofunctional aliphatic urethane acrylate. In some embodiments, the monofunctional aliphatic urethane acrylate is present in an amount of from 3 wt% to 40 wt%, based on the total weight of the adhesive composition. In some embodiments, the monofunctional aliphatic urethane acrylate is a monomer. In some embodiments, the monofunctional aliphatic urethane acrylate monomer is present in an amount of from 20 to 40 wt%, based on the total weight of the adhesive composition. In some embodiments, the monofunctional aliphatic urethane acrylate is present in an amount of from 20 to 35 wt%, from 20 to 30 wt%, from 25 to 40 wt%, from 30 to 40 wt%, or from 35 to 40 wt%, based on the total weight of the adhesive composition. In some embodiments, the monofunctional aliphatic urethane acrylate is an oligomer. In some embodiments, the monofunctional aliphatic urethane acrylate oligomer is present in an amount of from 3 to 15 wt%, based on the total weight of the adhesive composition. In some embodiments, the monofunctional aliphatic urethane acrylate oligomer is present in an amount of from 3 to 10 wt% or from 3 to 5 wt%, based on the total weight of the adhesive composition. In some embodiments, the monofunctional aliphatic urethane acrylate is a monomer. In some embodiments, the monofunctional aliphatic urethane acrylate has a Tg of from -80 to 0 °C. In someembodiments, the multifunctional aliphatic urethane acrylate has viscosity of from 20 to 60 mPa.s; from 25 to 50 mPa.s, from 30 to 50 mPa.s at 25 °C. Examples of commercially available monofunctional aliphatic urethane acrylates include but are not limited to Photomer 4184 (commercially available from IGM Resins located in Netherlands); Genomer 1122 and Genomer 4188 / EHA (commercially available from Rahn-Group located in Switzerland).

[0038] The composition includes at least one UV reactive adhesion promoter. The UV reactive adhesion promoter improves the adhesion properties and temperature resistance of the PSA. Any suitable adhesion promoter can be used. In some embodiments, the UV reactive adhesion promoter is at least one of a (meth)acrylic acid, Beta-carboxyethyl acrylate, 2-hydroxyethyl acrylate, N-vinyl pyrrolidone, N-vinyl caprolactam, vinyl methyl oxazolidinone, methacryloxy functional trimethoxy silane, vinyltrimethoxysilane, methacrylated phosphate ester, and any combination thereof.

[0039] The composition includes at least one multifunctional thiol. The multifunctional thiol enables the construction of the highly branched polymer chain architecture of the PSA, enhancing the adhesive's pressure sensitive adhesion and temperature resistance. In some embodiments, the multifunctional thiol has a functionality of greater than 2. In some embodiments, the multifunctional thiol has a functionality of from 2 to 6. In some embodiments, the multifunctional thiol is a difunctional thiol. In some embodiments, the multifunctional thiol is a trifunctional thiol. In some embodiments, the multifunctional thiol is selected from at least one of a tetraethylene glycol bis(3-mercaptopropionate, pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrathioglycolate, pentaerythritol tetrathiolactate, pentaerythritol tetrathiobutyrate, dipentaerythritol Hexakis(3-mercaptopropionate), dipentaerythritol hexathioglycolate, trimethylolpropane tris(3-mercaptopropionate), and tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate, tripentaerythritol octa(3-mercaptopropionate), tripentaerythritol octathioglycolate and any combination thereof.

[0040] The multifunctional acrylate provides the adhesive composition with enhanced temperature resistance. The multifunctional acrylate links highly branched polymer chains generated by the multifunctional thiol, thereby completing the assembly of the adhesive's polymer architecture. In some embodiments, the multifunctional acrylate includes from 2 to 8 functional groups. In some embodiments, the multifunctional acrylate includes from 2 to 6 functional groups. The adhesive viscosity can be adjusted by adjusting the amount of the multifunctional acrylate. In some embodiments, the multifunctional acrylate is selected at least one of a hexanediol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate,ethoxylated hexanediol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate and any combination thereof.

[0041] As noted previously, the multifunctional thiol and multifunctional acrylate generate the polymer architecture of the adhesive. The ratio of each of these components influences the final polymer architecture. In some embodiments, the weight ratio of the multifunctional acrylate to the multifunctional thiol is 1:7 to 3:1. In some embodiments, the ratio of the multifunctional acrylate to the multifunctional thiol is 1:1 to 1:4, 2:1 to 1:2, or 3:1 to 1:1.3.

[0042] In some embodiments, at least 30 wt% of the adhesive includes the multifunctional aliphatic urethane acrylate, the multifunctional acrylate, and the multifunctional thiol.

[0043] In some embodiments, the adhesive composition further includes a monofunctional acrylate. In some embodiments, the monofunctional acrylate is selected from the group of an acrylic acid adduct of the epoxy ester of a highly branched and aliphatic structure, monofunctional aliphatic acrylate, ethoxylated aromatic acrylate, dihydrodicyclopentadienyl acrylate, isobornyl acrylate, and any combination thereof.

[0044] In some embodiments, the adhesive further includes a photoinitiator. In some embodiments, the adhesive further includes at least one photoinitiator. In some embodiments, the adhesive further includes at least two photoinitiators. In some embodiments, the adhesive further includes two photoinitiators. In some embodiments, the photoinitiators have different wavelengths. The use of two or more photoinitiators that are capable of absorbing different wavelengths enables a higher line speed during manufacturing, as the ability of the photoinitiators within the adhesive to absorb multiple wavelengths ensures the generation of free radicals to initiate crosslinking, thereby providing efficient curing of the adhesive. Suitable photonitiators include, for example, phosphine oxides; benzophenone and substituted benzophenones, acetophenone and substituted acetophenones, benzoin and its alkyl ethers and combinations thereof.

[0045] The adhesive composition can be coated onto a substrate by any suitable method. In some embodiments, the adhesive composition is suitable for deposition on a substrate by at least one of flexo printing, inkjet printing, screen printing, spraying, die coating, gravure printing, narrow web printing, wide web printing, or letterpress printing. Generally, the deposition method will depend on the viscosity of the adhesive. The adhesive can be coated at any suitable thickness. The coatingthickness will depend on the viscosity of the adhesive. In some embodiments, the adhesive is coated onto a substrate at a thickness of 5 to 50 (gram / m2), 10 to 40 gsm, 15 to 35 gsm, or 20 to 30 gsm.

[0046] In some embodiments, the adhesive has a viscosity of from about 500 to about 10000 cPs at room temperature. In some embodiments, the adhesive composition has a viscosity of less than 10000 cPs at room temperature. In some embodiments, the adhesive composition has a viscosity of less than 5000 cPs at room temperature. In some embodiments, the adhesive composition has a viscosity of less than 1000 cPs at room temperature. In some embodiments, the adhesive composition has a viscosity of from 500 to 9000, 1000 to 8000, 1500 to 7000, 2000 to 6000, 2500 to 5000, or 3000 to 4000 cPs at room temperature. In some embodiments, the adhesive is applied at a temperature greater than room temperature, in order to lower the viscosity upon application.

[0047] In some embodiments, the adhesive composition is a 100% solids adhesive. In some embodiments, the adhesive composition is a substantially 100% solids adhesive. In some embodiments, the adhesive composition contains no non-reactive carrier. In some embodiments, the adhesive composition further includes a non-reactive carrier.

[0048] In some embodiments, the adhesive composition can further include additional additives, such as for example, tackifiers, inhibitors, fillers, pigments, plasticizers, wetting agents, rheology modifiers and defoamers.

[0049] The adhesive composition is suitable for multiple applications, such as for example, insulation, durable goods, automotive, radio frequency identification devices, electronics, specialized tags, labels and tapes for high temperature use, graphics, industrial, medical, retail, consumer goods, packaging, home care, personal care, and food and beverage. The adhesive can be used in applications where it will be exposed to high temperatures, due to its high temperature resistance. In some embodiments, the adhesive composition is resistant to temperatures of greater than 200 °C. In some embodiments, the adhesive composition is resistant to temperatures of greater than 250 °C.

[0050] The adhesive composition can be made by any suitable means known to those skilled in the art. In some embodiments, the adhesive is made by a method of providing a crosslinkable mixture comprising: 20 to 50 wt% of a multifunctional aliphatic urethane acrylate, wherein the multifunctional aliphatic urethane acrylate comprises 2 to 3 functional groups; 3 to 40 wt% of a monofunctional aliphatic urethane acrylate; 5 to 15 wt% of a UV reactive adhesion promoter; 5 to 20 wt% of a multifunctional thiol; and 3 to 15% of a multifunctional acrylate; mixing the crosslinkablemixture; and exposing the crosslinkable mixture to UV radiation, thereby forming the reaction product of the crosslinkable mixture.EXAMPLES

[0051] The present disclosure is further illustrated by the following examples, which in no way should be construed as being limiting. That is, the specific features described in the following examples are merely illustrative, and not limiting.Control

[0052] A 100% solids UV curable pressure sensitive adhesive commercially available from Avery Dennison Corporation (located in Ohio, USA) was provided. It had a viscosity of about 3000 cPs at 25 °C and required 40 mJ / cm2 of UV-C dosage to cure.Examples 1-3 and Comparative Examples 1-5

[0053] 100% solids UV curable compositions were prepared with the ingredients and amounts (weight percentage) as specified in the Table 1.

[0054] Table 1. Example Formulations

[0055] All of the ingredients were added one at a time into a glass reactor equipped with a reflux condenser, a thermocouple, and a pitched turbine agitator. Then the contents were brought to 60 °C under air and mixed well until the solution was homogeneous.

[0056] The viscosity of some examples was measured at 25 °C by a Brookfield viscometer with Spindle #3 at 12 RPM and tabulated in Table 2 below:

[0057] Table 2. Viscosity of 100% solids UV curable pressure sensitive adhesivesPressure Sensitive Adhesion Testing

[0058] For pressure sensitive adhesion performance characterization, each formulation was directly coated onto a 50 micron thick MYLAR® at a dry coat weight of 15 g / m2 (grams per square meter), and crosslinked with a UV-C dosage of 15 mJ / cm2 except the control which was crosslinked with a UV-C dosage of 40 mJ / cm2.

[0059] Pressure sensitive adhesion performance was characterized by measuring 90° peel adhesion, loop-tack, and static shear. 90° Peel adhesion values were measured in Ib / inch at room temperature at 12 inch / minute crosshead speed after the specified dwell time (i.e., 15 minutes) on stainless steel panels. Loop-tack was measured on stainless steel panels, and used to determine adhesion of a pressure sensitive adhesive to a surface after a very short dwell time under minimum application pressure. Static shear values (time durations in minutes until failure) were measured at room temperature using 1 / 2 inch x 1 / 2 inch contact area with 250 gram weight on stainless steel panels. All tests were performed in a controlled environment room of 22 °C and 50% relative humidity.SAFT Measurement

[0060] SAFT (shear adhesion failure temperature) was used to determine the upper temperature limit at which a pressure sensitive adhesive will fail when a constant shear force (forceexerted by weight alone without motion) is applied while the temperature is increased at a constant rate. The shear force was applied with a 1 kilogram weight on stainless steel panels at a contact area of 1 inch x 1 inch. After 10 minute dwell time at 40 °C after the weight was hung, the test then started and the temperature was raised 1 °C every 30 seconds, until it reached the final temperature of 200 °C, or the adhesive failed.

[0061] The pressure sensitive adhesion performance of the adhesive samples prepared from the Examples are presented in Table 3, which includes 90° peel adhesion, loop-tack, static shear performance and SAFT.

[0062] Table 3. Adhesion performance of adhesive samples:Failure Mode:1Cohesive failure;2Light residue;3Adhesive failure

[0063] As can be seen, the present subject matter displayed remarkably higher temperature resistance than the Control and the Comparative Examples as evidenced by the higher SAFT. In the meantime, the subject matter was also characterized by a well-balanced peel adhesion and static shear resistance in comparison to the Control and the Comparative Examples. Moreover, the present subject matter can be properly cured with much less UV-C dosage than the Control while exhibiting well balanced peel adhesion and static shear, demonstrating the adhesive's high line-speed capability.

[0064] The features, structures, or characteristics of the invention described throughout this specification may be combined in any suitable manner in one or more aspects. For example, reference throughout this specification to "certain aspects," "some aspects," "some embodiments," certain embodiments," or similar language means that a particular feature, structure, or characteristic described in connection with the aspect is included in at least one aspect of the present invention.Thus, appearances of the phrases "in certain aspects," "in some aspect," "in other aspects," "in certain embodiments," "in some embodiments," "in other embodiments," or similar language throughout this specification do not necessarily all refer to the same group of aspects or embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more aspects or embodiments.

[0065] As described hereinabove, the present subject matter solves many problems associated with previous strategies, systems and / or devices. However, it will be appreciated that various changes in the details, materials and arrangements of components and / or operations, which have been herein described and illustrated in order to explain the nature of the present subject matter, may be made by those skilled in the art without departing from the principle and scope of the claimed subject matter, as expressed in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An adhesive composition comprising the crosslinkable reaction product of a mixture comprising:20 to 50 wt% of a multifunctional aliphatic urethane acrylate, wherein the multifunctional aliphatic urethane acrylate comprises 2 to 3 functional groups,3 to 40 wt% of a monofunctional aliphatic urethane acrylate,5 to 15 wt% of a UV reactive adhesion promoter,5 to 20 wt% of a multifunctional thiol, and3 to 15% of a multifunctional acrylate.

2. The adhesive composition according to claim 1, wherein the multifunctional aliphatic urethane acrylate is an oligomer.

3. The adhesive composition according to claim 1, wherein the multifunctional aliphatic urethane acrylate has a Tg of from -80 to 0 °C.

4. The adhesive composition according to claim 1, wherein the monofunctional aliphatic urethane acrylate is an oligomer.

5. The adhesive composition according to claim 1, wherein the monofunctional aliphatic urethane acrylate is a monomer.

6. The adhesive composition according to claim 1, wherein the monofunctional aliphatic urethane acrylate has a Tg of from -80 to 0 °C.

7. The adhesive composition according to claim 1, wherein the UV reactive adhesion promoter is selected from the group consisting of a (meth)acrylic acid, Beta-carboxyethyl acrylate, 2- hydroxyethyl acrylate, N-vinyl pyrrolidone, N-vinyl caprolactam, vinyl methyl oxazolidinone, methacryloxy functional trimethoxysilane, vinyltrimethoxysilane, methacrylated phosphate ester, and any combination thereof.

8. The adhesive composition according to claim 1, wherein the multifunctional thiol comprises a functionality of greater than 2.

9. The adhesive composition according to claim 1, wherein the multifunctional thiol comprises a functionality of from 2 to 8.

10. The adhesive composition according to claim 1, wherein the multifunctional thiol is selected from the group consisting of tetraethylene glycol bis(3-mercaptopropionate), pentaerythritoltetrakis(3-mercaptopropionate), pentaerythritol tetrathioglycolate, pentaerythritol tetrathiolactate, pentaerythritol tetrathiobutyrate, dipentaerythritol Hexakis(3- mercaptopropionate), dipentaerythritol hexathioglycolate, trimethylolpropane tris(3- mercaptopropionate), and tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate, tripentaerythritol octa(3-mercaptopropionate), tripentaerythritol octathioglycolate and any combination thereof.

11. The adhesive composition according to claim 1, further comprising a monofunctional acrylate.

12. The adhesive composition according to claim 11, wherein the monofunctional acrylate is selected from the group consisting of an acrylic acid adduct of the epoxy ester of a highly branched and aliphatic structure, monofunctional aliphatic acrylate, ethoxylated aromatic acrylate, dihydrodicyclopentadienyl acrylate, isobornyl acrylate, and any combination thereof.

13. The adhesive composition according to claim 1, having a weight ratio of the multifunctional acrylate to the multifunctional thiol of from 1:7 to 3:1.

14. The adhesive composition according to claim 1, wherein at least 30 wt% of the adhesive composition is the multifunctional aliphatic urethane acrylate, the multifunctional acrylate, and the multifunctional thiol.

15. The adhesive composition according to claim 1, further comprising a photoinitiator.

16. The adhesive composition according to claim 1, further comprising at least 2 photoinitiators.

17. The adhesive composition according to claim 1, wherein the adhesive composition is suitable for deposition on a substrate by at least one of flexo printing, inkjet printing, screen printing, spraying, die coating, gravure printing, narrow web printing, wide web printing, and letter press printing.

18. The adhesive composition according to claim 1, wherein the adhesive composition has a viscosity of from about 500 to about 10000 cPs at room temperature.

19. A method of making the adhesive composition according to claim 1, comprising the steps of: i. providing a crosslinkable mixture comprising:20 to 50 wt% of a multifunctional aliphatic urethane acrylate, wherein the multifunctional aliphatic urethane acrylate comprises 2 to 3 functional groups;3 to 40 wt% of a monofunctional aliphatic urethane acrylate;5 to 15 wt% of a UV reactive adhesion promoter;5 to 20 wt% of a multifunctional thiol; and3 to 15% of a multifunctional acrylate; ii. mixing the crosslinkable mixture; and ill. exposing the crosslinkable mixture to UV radiation, thereby forming the reaction product of the crosslinkable mixture.

20. An article comprising the adhesive composition according to claim 1.

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