Uv-curable adhesives and related methods

Abstract

Pressure sensitive adhesives including an architectural polymer are described. Methods of producing the polymer and the pressure sensitive adhesive are also described. In addition, articles including the pressure sensitive adhesive are also described.

Description

[0001] Cross-reference to related applications This application claims the benefit of U.S. Provisional Application No. 63 / 560,171, filed March 1, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This subject matter relates to methods for preparing structural polymers and pressure-sensitive adhesives comprising such polymers. This subject matter also relates to pressure-sensitive adhesives formed by this method. Furthermore, this subject matter relates to articles comprising the pressure-sensitive adhesive. Background Technology

[0003] Acrylic pressure-sensitive adhesives (PSAs) are used in high-performance applications due to their excellent balance between peel adhesion and cohesive strength. In many cases, acrylic PSAs are used in high-temperature applications. However, a drawback associated with conventional acrylic adhesives is that they typically possess either UV curing properties or high-temperature resistance. This is disadvantageous in applications where it is desirable to apply the PSA and then cure it via UV curing, while also requiring the PSA to withstand high temperatures during application and / or use.

[0004] Therefore, there is a need for acrylic polymers that are both UV-curable and heat-resistant. Furthermore, these polymers need to be customizable for different applications and capable of high-speed coating and crosslinking to form PSAs. Additionally, these polymers need to be less sensitive to cross-contamination and exposure to environmental conditions such as moisture. Finally, these polymers also need to have a high solids content. Summary of the Invention

[0005] The difficulties and drawbacks associated with previous methods are addressed in this topic as described below.

[0006] A first aspect of this disclosure provides an adhesive composition comprising a crosslinkable reactive product of a mixture comprising: 20 to 50 wt% of a polyfunctional aliphatic urethane acrylate, wherein the polyfunctional 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 adhesive accelerator, 5 to 20 wt% of a polyfunctional thiol, and 3 to 15 wt% of a polyfunctional acrylate.

[0007] Another aspect of this disclosure provides a method for preparing an adhesive composition according to the first aspect, comprising the steps of: providing a crosslinkable mixture comprising: 20 to 50 wt% of a polyfunctional aliphatic urethane acrylate, wherein the polyfunctional 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 adhesive accelerator; 5 to 20 wt% of a polyfunctional thiol; and 3 to 15 wt% of a polyfunctional acrylate; mixing the crosslinkable mixture; and exposing the crosslinkable mixture to UV radiation to form a reaction product of the crosslinkable mixture.

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

[0009] The compositions and methods described herein overcome the limitations of currently available products by producing high-temperature resistant, UV-curable, and customizable polymers for various applications. Detailed Implementation

[0010] I. Definition The accompanying drawings represent some, but not all, of the embodiments described herein. The claims should not be construed as limiting to the embodiments described herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. The same numerals consistently refer to the same elements.

[0011] In the specification and appended claims, unless the context clearly specifies otherwise, the singular forms “a”, “an”, and “the” include multiple referents.

[0012] As used herein, the terms “a”, “an”, “the”, “at least one”, and “one or more” are used interchangeably. Thus, for example, a composition comprising “an” additive can be interpreted as comprising “one or more” additives.

[0013] The terms "preferred" and "preferably" refer to embodiments of the invention that may provide certain benefits in certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are useless, and is not intended to exclude other embodiments from the scope of the invention.

[0014] Similarly, in this document, the representation of a numerical range by endpoints includes all numbers of a subset of values ​​within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). Furthermore, the disclosure of a range includes the disclosure of all subranges included within a wider range (e.g., 1 to 5 discloses 1 to 4, 1.5 to 4.5, and 1 to 2).

[0015] Unless otherwise stated, the terms "weight percent" or "wt%" refer to the concentration of a component or composition based on the total weight of the composition, expressed as a percentage.

[0016] Unless otherwise stated, 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,” “include,” “having,” “has,” “contain,” and their variations are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of other behaviors or structures.

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

[0019] As used herein, the term "aliphatic" is defined as including alkyl, alkenyl, alkynyl, haloalkyl, and cycloalkyl groups as described above. "Lower aliphatic" groups are branched or unbranched aliphatic groups having 1 to 10 carbon atoms.

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

[0021] As used herein, the term "aryl" refers to any carbonyl 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 incorporating at least one heteroatom into the ring of an aromatic group. Examples of heteroatoms include, but are not limited to, nitrogen, oxygen, sulfur, and phosphorus. An aryl group may be substituted with one or more groups, including but not limited to alkyl, alkynyl, alkenyl, aryl, halogen, nitro, amino, ester, ketone, aldehyde, hydroxyl, carboxylic acid, or alkoxy groups, or the aryl group may be unsubstituted.

[0022] As used herein, the term "cycloalkyl" refers to a non-aromatic carbonyl ring consisting 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, wherein at least one carbon atom of the ring is substituted with a heteroatom, such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorus.

[0023] As used herein, the term “oligomer” refers to a molecule with an average molecular weight (Mw) in the range of about 300 to about 40,000 g / mol.

[0024] The term "syrup" refers to a composition with a viscosity of 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 a temperature in the range of about 15°C to about 25°C, more typically about 22°C (72°F).

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

[0026] As used in this article, the term "multifunctional" refers to a product that includes more than one functional group.

[0027] As used in this article, the term "multifunctional" refers to a function that includes only one functional group.

[0028] As used herein, the term "polymer" can refer to a polymeric compound prepared by polymerizing the same or different types of monomers. The broader term "polymer" includes terms such as "homogeneous polymer," "copolymer," etc.

[0029] As used herein, the terms “derived from,” “prepared by reaction,” or “reaction product” refer to the product formed by the polymerization of monomers. That is, during polymerization, the monomers present in the polymer are chemically different from the unreacted monomers.

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

[0031] As used herein, the term "100% solids" refers to a composition that does not contain non-reactive carriers such as, for example, water or solvents, which may evaporate upon curing. Such compositions retain 100% of their bulk and shape after curing. Therefore, the wet film thickness (the thickness of the composition when wet-applied) of a 100% solids composition will be equal to or substantially equal to the dry film thickness (the thickness of the composition when cured and dried).

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

[0033] As used herein, the terms “architecture polymer,” “architectured polymer,” or “polymer architecture” in polymer science refer to polymers intentionally designed to exhibit properties that deviate from strictly linear polymer chains.

[0034] II. Crosslinkable reaction products Generally, this subject matter provides a UV-curable pressure-sensitive adhesive composition with high heat resistance. This adhesive composition can be applied at ambient temperature or high temperature.

[0035] The pressure-sensitive adhesive composition comprises a crosslinkable reactive product of a mixture comprising: 20 to 50 wt% of a polyfunctional aliphatic urethane acrylate, wherein the polyfunctional 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 adhesive accelerator; 5 to 20 wt% of a polyfunctional thiol; and 3 wt% to 15 wt% of a polyfunctional acrylate.

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

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

[0038] The composition includes at least one UV-reactive adhesive accelerator. The UV-reactive adhesive accelerator improves the adhesion and temperature resistance of the PSA. Any suitable adhesive accelerator can be used. In some embodiments, the UV-reactive adhesive accelerator is at least one of (meth)acrylic acid, β-carboxyethyl acrylate, 2-hydroxyethyl acrylate, N-vinylpyrrolidone, N-vinylcaprolactam, vinylmethyloxazolidinone, methacryloxy-functionalized trimethoxysilane, vinyltrimethoxysilane, methacrylated phosphate, and any combination thereof.

[0039] The composition includes at least one polyfunctional thiol. The polyfunctional thiol can construct the highly branched polymer chain architecture of the PSA, enhancing the pressure-sensitive adhesion and temperature resistance of the adhesive. In some embodiments, the polyfunctional thiol has a functionality greater than 2. In some embodiments, the polyfunctional thiol has a functionality of 2 to 6. In some embodiments, the polyfunctional thiol is a difunctional thiol. In some embodiments, the polyfunctional thiol is a trifunctional thiol. In some embodiments, the polyfunctional thiol is selected from at least one of tetraethylene glycol bis(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), pentaerythritol tetrathioglycolate, pentaerythritol tetrathiolactic acid ester, pentaerythritol tetrathiobutyrate, dipentaerythritol hexa(3-mercaptopropionate), dipentaerythritol hexathioglycolate, trimethylolpropane tri(3-mercaptopropionate), tris[2-(3-mercaptopropoxy)ethyl]isocyanurate, tripentaerythritol octa(3-mercaptopropionate), tripentaerythritol octathioglycolate, and any combination thereof.

[0040] Multifunctional acrylates provide enhanced temperature resistance to adhesive compositions. The multifunctional acrylates link highly branched polymer chains generated by multifunctional thiols, thereby completing the assembly of the polymeric architecture of the adhesive. In some embodiments, the multifunctional acrylates comprise 2 to 8 functional groups. In some embodiments, the multifunctional acrylates comprise 2 to 6 functional groups. The adhesive viscosity can be adjusted by regulating the amount of multifunctional acrylate. In some embodiments, the multifunctional acrylate is selected from at least one of the following: hexaethylene glycol 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 tetraaldehyde pentaacrylate, dipentaerythritol hexaacrylate, and any combination thereof.

[0041] As previously described, polyfunctional thiols and polyfunctional acrylates form the polymeric structure of the adhesive. The proportions of each of these components affect the final polymeric structure. In some embodiments, the weight ratio of polyfunctional acrylates to polyfunctional thiols is 1:7 to 3:1. In some embodiments, the ratio of polyfunctional acrylates to polyfunctional thiols 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 comprises polyfunctional aliphatic urethane acrylate, polyfunctional acrylate, and polyfunctional thiol.

[0043] In some embodiments, the adhesive composition further includes a monofunctional acrylate. In some embodiments, the monofunctional acrylate is selected from acrylate adducts of highly branched and aliphatic epoxy esters, monofunctional aliphatic acrylates, ethoxylated aromatic acrylates, dihydrodicyclopentadienyl acrylates, isobornyl acrylates, 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. Using two or more photoinitiators capable of absorbing different wavelengths allows for higher linear speeds during manufacturing because the ability of the photoinitiators in the adhesive to absorb multiple wavelengths ensures the generation of free radicals to initiate crosslinking, thereby providing efficient curing of the adhesive. Suitable photoinitiators include, for example, phosphine oxide; benzophenone and substituted benzophenones, acetophenone and substituted acetophenones, benzoin and its alkyl ethers, and combinations thereof.

[0045] The adhesive composition can be applied to the substrate by any suitable method. In some embodiments, the adhesive composition is suitable for deposition onto the substrate by at least one of flexographic printing, inkjet printing, screen printing, spraying, die coating, gravure printing, narrow-web printing, wide-web printing, or letterpress printing. Typically, the deposition method will depend on the viscosity of the adhesive. The adhesive can be applied at any suitable thickness. The coating thickness will depend on the viscosity of the adhesive. In some embodiments, the adhesive is applied at a thickness of 5 to 50 g / m³. 2 ), 10 to 40 gsm, 15 to 35 gsm or 20 to 30 gsm thickness are coated onto the substrate.

[0046] In some embodiments, the adhesive has a viscosity of about 500 to about 10,000 cPs at room temperature. In some embodiments, the adhesive composition has a viscosity of less than 10,000 cPs at room temperature. In some embodiments, the adhesive composition has a viscosity of less than 5,000 cPs at room temperature. In some embodiments, the adhesive composition has a viscosity of less than 1,000 cPs at room temperature. In some embodiments, the adhesive composition has a viscosity of 500 to 9,000, 1,000 to 8,000, 1,500 to 7,000, 2,000 to 6,000, 2,500 to 5,000, or 3,000 to 4,000 cPs at room temperature. In some embodiments, the adhesive is applied at a temperature above room temperature to reduce viscosity upon application.

[0047] In some embodiments, the adhesive composition is a 100% solid adhesive. In some embodiments, the adhesive composition is substantially 100% solid. In some embodiments, the adhesive composition does not contain a non-reactive carrier. In some embodiments, the adhesive composition further includes a non-reactive carrier.

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

[0049] This adhesive composition is suitable for a variety of applications, such as insulation, durable goods, automotive, RFID devices, electronics, high-temperature markings, labels and tapes, graphics, industrial, medical, retail, consumer goods, packaging, home care, personal care, and food and beverage. Due to its high-temperature resistance, the adhesive can be used in applications exposed to high temperatures. In some embodiments, the adhesive composition withstands temperatures greater than 200°C. In some embodiments, the adhesive composition withstands temperatures greater than 250°C.

[0050] The adhesive composition can be prepared by any suitable means known to those skilled in the art. In some embodiments, the adhesive is prepared by providing a crosslinkable mixture comprising: 20 to 50 wt% of a polyfunctional aliphatic urethane acrylate, wherein the polyfunctional 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 adhesive accelerator; 5 to 20 wt% of a polyfunctional thiol; and 3 to 15 wt% of a polyfunctional acrylate; mixing the crosslinkable mixture; and exposing the crosslinkable mixture to UV radiation to form a reaction product of the crosslinkable mixture.

[0051] Example This disclosure is further illustrated by the following embodiments, which should in no way be construed as limiting. That is, the specific features described in the following embodiments are merely illustrative and not limiting.

[0052] Comparison A 100% solid UV-curable pressure-sensitive adhesive is provided, commercially available from Avery Dennison Corporation (located in Ohio, USA). It has a viscosity of approximately 3000 cPs at 25°C and requires a UV-C dose of 40 mJ / cm² for curing.

[0053] Examples 1-3 and Comparative Examples 1-5 Prepare a 100% solid UV-curable composition using the components and amounts (by weight percentage) specified in Table 1.

[0054] Table 1. Example Recipes Add all ingredients one at a time to a glass reactor equipped with a reflux condenser, thermocouples, and a tilting turbine stirrer. Then heat the contents in air to 60°C and mix thoroughly until the solution is homogeneous.

[0055] The viscosity of some embodiments was measured at 25°C using a Brookfield viscometer at 12 RPM with a Spindle 3, and is listed in Table 2 below: Table 2. Viscosity of 100% Solid UV-Cureable Pressure-Sensitive Adhesives Pressure-sensitive adhesive test To characterize the pressure-sensitive adhesive properties, each formulation was directly coated onto a 50-micron-thick MYLAR film. ® The dry coating weighed 15 g / m² and was crosslinked with a UV-C dose of 15 mJ / cm², while the control was crosslinked with a UV-C dose of 40 mJ / cm².

[0056] Pressure-sensitive adhesive performance was characterized by measuring 90° peel strength, ring tack, and static shear force. The 90° peel strength, measured in pounds per inch (lb / in), was determined at room temperature after a specified dwell time (15 minutes) on a stainless steel panel, using a crosshead speed of 12 inches per minute. Ring tack was measured on the stainless steel panel and used to determine the adhesion of the pressure-sensitive adhesive to the surface after a very short dwell time at minimum application pressure. Static shear force (duration before failure, in minutes) was measured at room temperature using a 250-gram weight on a stainless steel panel with a 1 / 2-inch × 1 / 2-inch contact area. All tests were conducted in a controlled environment chamber at 22°C and 50% relative humidity.

[0057] SAFT measurement SAFT (Shear Bond Failure Temperature) is used to determine the upper temperature limit at which pressure-sensitive adhesives fail when a constant shear force (force applied solely by weight without movement) is applied while the temperature is increased at a constant rate. The shear force is applied to a stainless steel plate with a contact area of ​​1 inch x 1 inch, using a 1 kg weight. After suspending the weight and holding at 40°C for 10 minutes, the test begins, increasing the temperature by 1°C every 30 seconds until a final temperature of 200°C is reached, or until the adhesive fails.

[0058] The pressure-sensitive adhesive properties of the adhesive samples prepared by the examples are shown in Table 3, including 90° peel adhesion, ring adhesion, static shear properties and SAFT.

[0059] Table 3. Adhesive properties of adhesive samples: Failure Mode: 1 Cohesion failure; 2 Slight residue; 3 Adhesive failure As can be seen, this subject exhibits significantly higher temperature resistance than the control and comparative examples, which can be evidenced by the higher SAFT. Simultaneously, compared to the control and comparative examples, this subject also demonstrates a good balance between peel adhesion and static shear resistance. Furthermore, this subject can be properly cured with a much lower UV-C dosage than the control, while exhibiting a good balance between peel adhesion and static shear, demonstrating the high linear velocity capability of this adhesive.

[0060] The features, structures, or characteristics of the invention described herein can be combined in any suitable manner in one or more aspects. For example, references throughout this specification to “some aspects,” “some embodiments,” “some implementations,” or similar language mean that a particular feature, structure, or characteristic described in connection with that aspect is included in at least one aspect of the invention. Therefore, the appearance of the phrases “in some aspects,” “in some aspects,” and “in other aspects,” “in some implementations,” “in other implementations,” or similar language throughout this specification does not necessarily refer to all aspects or implementations of the same group, and the described features, structures, or characteristics can be combined in any suitable manner in one or more aspects or implementations.

[0061] As stated above, this subject matter addresses many problems associated with prior strategies, systems, and / or devices. However, it should be understood that various changes can be made by those skilled in the art to the details, materials, and arrangements of the components and / or operations described and illustrated herein to explain the nature of this subject matter, without departing from the principles and scope of the claimed subject matter as expressed in the appended claims.

Claims

1. An adhesive composition comprising a crosslinkable reactive product of a mixture, said mixture comprising: 20 to 50 wt% of multifunctional aliphatic urethane acrylate, wherein the multifunctional aliphatic urethane acrylate comprises 2 to 3 functional groups. 3 to 40 wt% monofunctional aliphatic urethane acrylate, 5 to 15 wt% UV reactive adhesive accelerator, 5 to 20 wt% polyfunctional thiols, and 3% to 15% of polyfunctional acrylates.

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

3. The adhesive composition according to claim 1, wherein the Tg of the polyfunctional aliphatic urethane acrylate is -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 Tg of the monofunctional aliphatic urethane acrylate is -80 to 0°C.

7. The adhesive composition according to claim 1, wherein the UV-reactive adhesive promoter is selected from (meth)acrylic acid, β-carboxyethyl acrylate, 2-hydroxyethyl acrylate, N-vinylpyrrolidone, N-vinylcaprolactam, vinylmethyloxazolidinone, methacryloxy-functionalized trimethoxysilane, vinyltrimethoxysilane, methacrylated phosphate, and any combination thereof.

8. The adhesive composition according to claim 1, wherein the polyfunctional thiol has a functionality greater than 2.

9. The adhesive composition according to claim 1, wherein the functionality of the polyfunctional thiol is 2 to 8.

10. The adhesive composition according to claim 1, wherein the polyfunctional thiol is selected from tetraethylene glycol bis(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), pentaerythritol tetrathioglycolate, pentaerythritol tetrathiolactic acid ester, pentaerythritol tetrathiobutyrate, dipentaerythritol hexa(3-mercaptopropionate), dipentaerythritol hexathioglycolate, trimethylolpropane tri(3-mercaptopropionate), 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 acrylate adducts of highly branched and aliphatic epoxy esters, monofunctional aliphatic acrylates, ethoxylated aromatic acrylates, dihydrodicyclopentadienyl acrylates, isobornyl acrylates, and any combination thereof.

13. The adhesive composition according to claim 1, wherein the weight ratio of the polyfunctional acrylate to the polyfunctional thiol is 1:7 to 3:

1.

14. The adhesive composition of claim 1, wherein at least 30 wt% of the adhesive composition is the polyfunctional aliphatic urethane acrylate, the polyfunctional acrylate, and the polyfunctional 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 two photoinitiators.

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

18. The adhesive composition of claim 1, wherein the viscosity of the adhesive composition at room temperature is about 500 to about 10,000 cPs.

19. A method for preparing the adhesive composition according to claim 1, comprising the following steps: i. Providing a crosslinkable mixture, the 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% monofunctional aliphatic urethane acrylate; 5 to 15 wt% UV-reactive adhesive accelerator; 5 to 20 wt% polyfunctional thiols; and 3 to 15% polyfunctional acrylates; ii. Mix the crosslinkable mixture; and iii. Exposing the crosslinkable mixture to UV radiation to form the reaction product of the crosslinkable mixture.

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

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