UV LED curable hot melt pressure sensitive adhesive composition

Abstract

The present invention relates to UV LED curable hot melt pressure sensitive adhesive compositions, methods for making same, and articles comprising a first substrate and a second substrate bonded together with the adhesive composition of the present invention.

Description

[Technical Field]

[0001] The present invention relates to UV LED curable hot melt pressure sensitive adhesive compositions, methods for making same, and articles comprising a first substrate and a second substrate bonded together with the adhesive composition of the present invention. [Background technology]

[0002] Hot melt adhesives offer several advantages over solvent-based adhesives in that they reduce or eliminate volatile organic compounds, have a long shelf life, and can usually be disposed of without special precautions. As pressure-sensitive adhesives, they are used in pressure-sensitive tapes, labels, glue dots, stickers, sticky note pads, automotive trim, and a variety of other products.

[0003] US 9,469,794 discloses a UV crosslinkable acrylic pressure sensitive adhesive comprising an acrylic copolymer and a cationic photoinitiator, the acrylic copolymer containing pendant reactive functional groups.

[0004] US 10,711,166 relates to a UV-curable adhesive composition comprising: a) a UV-curable acrylic polymer comprising at least one covalently bonded UV-reactive group, wherein at least one covalently bonded UV-reactive group is a benzophenone; b) a cationic photoinitiator; c) a photosensitizer; and d) an unsaturated oligomer, wherein the UV-curable acrylic polymer has the formula CH═CH(R 1 )(COOR 2 ), where R 1 is H or CH3, and R 2 is a branched or unbranched C1-20 alkyl chain.

[0005] US 8,796,350 refers to an ultraviolet-curable pressure-sensitive adhesive composition comprising an acrylic polymer and a cationic photoinitiator, said acrylic polymer being prepared from the group consisting of: (i) a compound of the formula CH═CH(R 1 )(COOR 2acrylic monomers consisting of acrylic acid or methacrylic acid derivatives of R 1 is H or CH3, and R 2 is a C alkyl chain; (ii) a monomer, wherein said monomer comprises a pendant reactive functional group selected from a cycloaliphatic epoxide, an oxetane, or a mixture thereof, and comprises about 0.001 to about 0.015 equivalents per 100 grams of said acrylic polymer, wherein said acrylic polymer is (a) essentially free of multi(meth)acrylates; and (b) has a T of less than 0° C. g and (c) a weight average molecular weight of about 50,000 to about 1,000,000 g / mol, wherein the ultraviolet-curable pressure-sensitive adhesive has a viscosity range of 1,000 to 500,000 mPa·s at 80 to 180°C.

[0006] In US 2019 / 0085221, in the first step, (i) a compound of the formula CH2=CH(R 1 )(COOR 2 R 3 CH3) n At least one acrylic monomer (R 1 is H or CH3, and R 2 and R 3 are both H or both CH3, and n is an integer from 0 to 22, or a mixture thereof), and (ii) at least one monomer comprising a pendant reactive functional group selected from cycloaliphatic epoxides, oxetanes, monosubstituted oxiranes, or mixtures thereof; and in a second step, reacting the mixture obtained in the first step with (iii) at least one cationic photoinitiator, and (iv) optionally further additives.

[0007] UV-curable pressure-sensitive adhesives are typically cured using standard mercury lamps as the radiation source. However, these bulbs consume large amounts of energy and are expected to be banned within the next few years due to their poor environmental profile in terms of energy consumption, lifespan, and the health hazards of mercury. Therefore, efforts are underway to develop pressure-sensitive hot melt adhesives that can be cured with other radiation sources, preferably LEDs.

[0008] In "Specific Cationic Photoinitiators for Near-UV and Visible LEDs: Iodonium vs. Ferrocenium Structures," published in the Journal of Applied Polymer Science, 2015, 42759, H. Mokbel et al. investigate two iodonium salts based on coumarin chromophores for polymerization with light-emitting diode irradiation (LED).

[0009] M. Rodrigues et al. conducted a study on the cationic photopolymerization of tetrahydrofuran initiated by irradiation of a solution containing sulfonium salts and thioxanthone in dichloromethane at 366 nm. The results are published in "Mechanistic study of tetrahydrofuran polymerization photoinitiated by sulfonium salt / thioxanthone systems," Macromol. Chem. Phys. 2001, 202, 2776-2782.

[0010] In their paper "Photopolymerization of Hybrid Monomers Part I: Comparison of the Performance of Selected Photoinitiators in Cationic and Free Radical Polymerization of Hybrid Monomers" published in Polymer Testing 64 (2017) 313-320, D. Nowak et al. report on the photopolymerization of the hybrid monomers 3,4-epoxycyclohexylmethyl methacrylate and 2-(2-vinyloxyethoxy)ethyl acrylate using a fluorescent probe method.

[0011] When adapting current systems to be cured with radiation sources other than mercury lamps, several aspects need to be taken into consideration, including that the hot melt adhesive must be able to cure effectively at the high belt speeds of industrial coaters and must be temperature stable up to 130°C.

[0012] Current efforts are limited by the poor absorption of commercially available cationic photoinitiators in the UVA region. While efforts have been made to overcome the poor absorption patterns by using modified iodonium salts or by using standard iodonium salts in combination with sensitizers, both approaches have proven inapplicable to hot-melt adhesives because they result in unstable products at high temperatures. Furthermore, these systems have proven unsuitable for high-speed curing in industrial coaters, where independence from dark cure is crucial. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] U.S. Patent No. 9,469,794 [Patent Document 2] U.S. Patent No. 10,711,166 [Patent Document 3] U.S. Patent No. 8,796,350 [Patent Document 4] US Patent Application Publication No. 2019 / 0085221 [Non-patent literature]

[0014] [Non-Patent Document 1] Journal of Applied Polymer Science, 2015, 42759 [Non-patent document 2] Macromol. Chem. Phys. 2001, 202, 2776-2782 [Non-patent document 3] Polymer Testing 64 (2017) 313-320 Summary of the Invention [Problem to be solved by the invention]

[0015] Therefore, there remains a need for hot melt pressure-sensitive adhesives that can be cured with UV-LEDs at the high belt speeds of industrial coaters. It is therefore an object of the present invention to address this need and to provide a UV-LED curable hot melt pressure-sensitive adhesive for industrial applications. [Means for solving the problem]

[0016] In the course of the present invention, it has surprisingly been found that this object is solved by a composition comprising an acrylic epoxy copolymer in combination with a specific photoinitiator / photosensitizer system.

[0017] The first subject of the invention is therefore a method for producing a medicament for the treatment of a malaria parasite comprising: a. Acrylic-epoxy-copolymer; b. at least one sulfonium salt photoinitiator, and c. at least one thioxanthone photosensitizer and a UV-LED curable hot melt pressure sensitive adhesive composition comprising: [Effects of the Invention]

[0018] It has been found that the adhesive composition of the present invention can be cured under LED irradiation, even at high belt speeds, and therefore does not require a mercury lamp. DETAILED DESCRIPTION OF THE INVENTION

[0019] In a preferred embodiment of the present invention, the acrylic-epoxy copolymer is prepared from a monomeric acrylic mixture copolymerized with a cycloaliphatic epoxide. Preferably, the acrylic mixture has the general structure (I): [ka] [In the formula, R 1 is C1-C18 alkyl or H, R 2 is H or CH3, R 3 is H or CH3, n is an integer between 0 and 18. and at least one aliphatic acrylic monomer.

[0020] Preferably, the acrylic monomer mixture comprises at least one hard acrylic monomer and at least one soft acrylic monomer. Thus, in one preferred embodiment, the monomer acrylic mixture comprises at least one first acrylate selected from the group consisting of methyl acrylate, ethyl acrylate, and isobutyl acrylate, and at least one second acrylic monomer selected from the group consisting of 2-ethylhexyl acrylate, n-butyl acrylate, 2-propylheptyl acrylate, and isodecyl acrylate.

[0021] The acrylic epoxy copolymer contained in the adhesive composition of the present invention comprises an acrylic monomer and a copolymer having the general structure (II): [ka] [In the formula, R 1 is C1-C18 alkyl or H, R 2 is C1-C18 alkyl or C1-C18 alkoxy, R 3 is a cycloaliphatic epoxy or epoxy group] and at least one epoxy acrylic monomer.

[0022] Preferably, the at least one epoxy acrylic monomer is selected from the group consisting of 3,4-epoxycyclohexylmethyl methacrylate or glycidyl methacrylate.

[0023] The acrylic epoxy copolymer is preferably obtained by solution polymerization, and the preferred solvent is selected from the group consisting of ethyl acetate, butanone, heptane, hexane, pentanone, acetone, toluene, propyl acetate, benzene, and mixtures thereof.

[0024] The molecular weight of the acrylic epoxy copolymer may be adjusted as needed, but it is preferred that the weight average molecular weight M be 50,000 to 400,000 Da, preferably 50,000 to 250,000 Da, as measured by GPC using a polystyrene standard. w It is preferable to maintain it within the range of

[0025] The adhesive composition of the present invention comprises at least one sulfonium salt photoinitiator. In a preferred embodiment, the sulfonium salt photoinitiator is represented by the general formula (III): [ka] [In the formula, R 1 is selected from H, aryl, thioaryl, C1-C18 alkyl, C1-C18 alkoxy, SH or NR2; R 2 is selected from P, Sb, B, As, or Bi; R 3 is F 6- or F3 (C2F5) 3- is] It is expressed as:

[0026] In one particularly preferred embodiment, the at least one sulfonium salt photoinitiator is selected from the group consisting of ([1,1'-biphenyl]-4-yl)(diphenyl)sulfonium trifluoro[tris(pentafluoroethyl)]phosphate or triarylsulfonium hexafluoroantimonate salts.

[0027] In addition to at least one sulfonium salt-based photoinitiator, the adhesive composition also contains at least one thioxanthone-based photosensitizer. In particular, it has been surprisingly found that the combination of a sulfonium salt-based photoinitiator and a thioxanthone-based photosensitizer with an acrylic epoxy copolymer provides a hot melt pressure-sensitive adhesive that can be easily cured under UV-LED irradiation. In a preferred embodiment, the at least one thioxanthone-based photosensitizer is represented by the general formula (IV): [ka] [In the formula, R 1 is NH, CH, S or O, R 2 ~R 9 are independently H, C1-C18 alkyl or isoalkyl, C1-C18 alkoxy, aryl, COOH, OH, NR2, COOR, urea, urethane, S, or SH; R 2 ~R 9 may consist of a polymerizable group in the structure ABC, where: A is O, NR2, S, C1-C18 alkyl or isoalkyl, COOH, C1-C18 alkoxy, S or aryl; B is C1-C18 alkyl or isoalkyl, carboxy, vinylic, or aryl; C is acrylic or methacrylic, epoxy or cycloaliphatic epoxy, vinylic or aryl. It is expressed as:

[0028] In one particularly preferred embodiment of the present invention, the thioxanthone photosensitizer is selected from the group consisting of isopropylthioxanthone, 2,4-diethyl-9H-thioxanthen-9-one, or derivatives thereof.

[0029] The adhesive composition of the present invention may contain further additives such as plasticizers, tackifiers, antioxidants, and fillers. Surprisingly, it has been found that conventional additives can be used without affecting the UV-LED curability of the adhesive composition of the present invention.

[0030] The adhesive optionally contains one or more suitable tackifiers (in an amount of about 10-50% by weight of the adhesive), which are commonly used in the manufacture of PSAs. Reference may be made explicitly to the "Handbook of Pressure-Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, 1989) or to the state of the art in any PSA-related literature. Generally, any natural resin compatible with the corresponding acrylic polymer may be used, and in particular all natural resins. Non-limiting examples include pinene resins, indene resins, rosin, terpene resins, terpene-phenolic resins, gum rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, polymerized rosin, and their disproportionated and esterified derivatives and salts.

[0031] Other suitable tackifiers include aliphatic and aromatic hydrocarbon resins, hydrogenated hydrocarbon resins, and functional hydrocarbon resins. Non-limiting examples include aliphatic and aromatic hydrocarbon resins, C5 resins, C9 resins, and other hydrocarbon resins. Any desired combination of these resins may be used to tailor the properties of the resulting PSA according to the desired final properties.

[0032] Specific examples of these tackifiers include TECKROS R86, SYLVALITE RE 85GB, FORAL 85-E, WING TACK 95, and CLEARTACK W85. A preferred embodiment of the tackifier is a liquid tackifier that can further reduce the viscosity of the adhesive. Examples include polymerized C5 petroleum feedstreams and polyterpenes, such as WING TACK 10 and ESCOREZ 2520, and the liquid rosin ester tackifier SYLVALITE 2038.

[0033] Hot melt adhesives are characterized by being solid at room temperature. They are applied in a molten state at elevated temperatures. To save valuable energy, hot melt adhesives are preferably applicable at relatively low temperatures. While conventional hot melt adhesives typically require temperatures of approximately 160-175°C, it has surprisingly been found that the hot melt adhesive compositions of the present invention can be applied at much lower temperatures. Thus, in a preferred embodiment, the adhesive composition of the present invention is characterized by an application temperature of 60-150°C, preferably 100-130°C, and more preferably 110-120°C.

[0034] The adhesive composition of the present invention is intended for industrial-scale application, particularly application using industrial coaters. To be compatible with existing systems, the curing temperature of the hot-melt adhesive composition should be within the temperature range normally associated with mercury lamp curing. Surprisingly, it has been found that this requirement is met by the adhesive composition of the present invention, despite the fact that curing is initiated by UV-LED. Thus, in one preferred embodiment, the hot-melt pressure-sensitive adhesive composition of the present invention has a curing temperature of 25 to 150°C, preferably 25 to 110°C.

[0035] The hot melt adhesive compositions of the present invention are designed for use in combination with the fast belt speeds of industrial coaters. To facilitate easy application, the viscosity of the adhesive compositions of the present invention is preferably 10,000 to 130,000 mPa at 120°C, as measured by a Brookfield DV-II, SP.27. * s, and more preferably 20,000 to 100,000 mPas at 120°C.

[0036] Furthermore, the hot melt pressure sensitive adhesive composition of the present invention is UV curable, in particular by UV radiation generated by LEDs. Thus, in one preferred embodiment, the adhesive composition has a UV radiation of 100 to 10,000 mJ / cm2, as measured by UV radiation measurement Puk measurement (here EIT Power Puk II). 2 , preferably 300 to 3,000 mJ / cm 2 Being able to cure at a given UVA dose eliminates the need for mercury lamps and allows for the use of more energy efficient LEDs.

[0037] In a preferred embodiment, the adhesive composition of the present invention is characterized in that the cured adhesive has a shear adhesion failure temperature (SAFT) of 50 to 200°C, preferably 120 to 200°C, measured according to GTF 6001 (Afera 5013).

[0038] In addition to being UV-LED curable, the adhesive compositions of the present invention further exhibit excellent adhesive properties upon curing. In a preferred embodiment, the cured adhesive exhibits a 180° peel performance of 2-45 N / 25 mm, preferably 5-35 N / 25 mm, at 300 mm / min on a steel substrate, as measured according to DIN ES ISO 11339 / 2010-06. Thus, a cured polymer film 15-150 gsm thick exhibits a 100-5,000 mJ / cm². 2 It is irradiated with.

[0039] A further subject of the present invention is a method for producing the hot-melt pressure-sensitive adhesive composition of the present invention. According to the method of the present invention, an acrylic monomer mixture is copolymerized with a cycloaliphatic epoxide, and the resulting acrylic-epoxy copolymer is blended with at least one sulfonium salt photoinitiator and at least one thioxanthone photosensitizer to obtain an adhesive composition. The copolymerization in solution allows crosslinking of the polymer by cationic polymerization.

[0040] The solvent used is preferably selected from the group consisting of ethyl acetate, butanone, heptane, hexane, pentanone, acetone, toluene, propyl acetate, benzene, and mixtures thereof.

[0041] The acrylic monomer mixture and the alicyclic epoxide are preferably copolymerized in the presence of a polymerization initiator. The polymerization initiator is preferably selected from the group consisting of azo initiators such as AIBN, AMBN, or ACCN. The polymerization initiator is preferably used in an amount of 0.01 to 5% based on the total weight of the acrylic monomer mixture and the alicyclic epoxide.

[0042] In one preferred embodiment, the method of the present invention comprises the steps of copolymerizing an acrylic monomer mixture and a cycloaliphatic epoxide, preferably in the presence of a polymerization initiator, in a solvent polymerization, followed by combining the resulting copolymer with a sulfonium salt-based photoinitiator and a thioxanthone-based photosensitizer, and obtaining the adhesive composition of the present invention after removing the solvent.

[0043] The sulfonium salt photoinitiator is preferably used in an amount of 0.001 to 5% by weight, more preferably 0.001 to 3.5% by weight, based on the total weight of the adhesive composition.

[0044] The thioxanthone photosensitizer is preferably used in an amount of 0.001 to 5% by weight, more preferably 0.001 to 3.5% by weight, based on the total weight of the adhesive composition.

[0045] A further subject of the present invention is an article obtainable using the hot-melt pressure-sensitive adhesive composition of the present invention. The article comprises a first substrate and a second substrate bonded to each other with the adhesive composition according to the present invention. In a preferred embodiment, the article is selected from the group consisting of a polymer foil substrate, a polymer substrate, a metal substrate, a glass substrate, or a wood or paper substrate. [Example]

[0046] The present invention will now be described in further detail with reference to the following examples, which are not to be construed as limiting the scope and spirit of the invention in any way.

[0047] Example 1: Preparation of UV-curable polymer An acrylic copolymer was prepared by free radical copolymerization of approximately 45% by weight of methyl acrylate and 54% by weight of 2-EHA. Approximately 1% by weight of epoxy acrylate M100 was then copolymerized. The polymerization was carried out in ethyl acetate and initiated using an azo initiator such as AIBN (0.11%). After polymerization, the polymer was combined with 0.5 g of Irganox 1726, 0.5 g of cationic photoinitiator CPI200K (50% solution in propylene carbonate), and 0.25 g of isopropylthioxanthone (ITX) as a sensitizer. The ethyl acetate was then removed under reduced pressure at 120°C to yield the acrylic copolymer. The weight-average molecular weight of the acrylic polymer was 120,000 Da (GPC), and the hot-melt viscosity (Brookfield, S27) of the polymer was 50,000 mPa at 120°C. * It is s.

[0048] Example 2: Preparation of UV-curable polymer An acrylic copolymer was prepared by free radical copolymerization of approximately 45% by weight of methyl acrylate and 54% by weight of 2-EHA. Approximately 2% by weight of epoxy acrylate M100 was then copolymerized. The polymerization was carried out in ethyl acetate and initiated using an azo initiator such as AIBN (0.11% by weight). After polymerization, the polymer was combined with 0.5 g of Irganox 1726, 0.5 g of cationic photoinitiator Omnicat 320 (50% solution in propylene carbonate), and 0.25 g of isopropylthioxanthone (ITX) as a sensitizer. The ethyl acetate was then removed under reduced pressure at 120°C to yield the acrylic copolymer. The weight-average molecular weight of the acrylic polymer was 110,000 Da (GPC), and the hot-melt viscosity (Brookfield, S27) of the polymer was 75,000 mPa at 110°C. * It is s.

[0049] Example 3: Preparation of UV-curable polymer An acrylic copolymer was prepared by free radical copolymerization of approximately 45% by weight of ethyl acrylate and 54% by weight of 2-propylheptyl acrylate. Approximately 1-2% by weight of epoxy acrylate M100 was then copolymerized. The polymerization was carried out in ethyl acetate and initiated using an azo initiator such as AIBN (0.11% by weight). After polymerization, the polymer was combined with 0.5 g of Irganox 1726, 0.5 g of cationic photoinitiator Omnicat 320 (50% solution in propylene carbonate), and 0.25 g of isopropylthioxanthone (ITX) as a sensitizer. The solvent was then removed under reduced pressure at 120°C to yield the acrylic copolymer. The weight-average molecular weight of the acrylic polymer was 120,000 Da (GPC), and the hot-melt viscosity (Brookfield, S27) of the polymer was 50,000 mPa at 120°C. * It is s.

[0050] Example 4: Preparation of UV-curable polymer An acrylic copolymer was prepared by free radical copolymerization of 45% by weight of methyl acrylate and 54% by weight of isodecyl acrylate. Approximately 1-2% by weight of epoxy acrylate M100 was then copolymerized. The polymerization was carried out in ethyl acetate or butanone and initiated using an azo initiator such as AIBN (0.11% by weight). After polymerization, the polymer was combined with 0.5 g of Irganox 1726, 1 g of cationic photoinitiator Omnicat 320 (50% solution in propylene carbonate), and 0.5 g of isopropylthioxanthone (ITX) as a sensitizer. The solvent was then removed under reduced pressure at 120°C to yield the acrylic copolymer. The weight-average molecular weight of the acrylic polymer was 120,000 Da (GPC), and the hot-melt viscosity (Brookfield, S27) of the polymer was 50,000 mPa at 120°C. * It is s.

[0051] Example 5: Preparation of UV-curable polymer An acrylic copolymer was prepared by free radical copolymerization of 45% by weight of methyl acrylate and 54% by weight of 2-EHA. Approximately 1-2% by weight of epoxy acrylate M100 was then copolymerized. The polymerization was carried out in ethyl acetate or butanone and initiated using an azo initiator such as AIBN (0.11% by weight). After polymerization, the polymer was combined with 0.5 g of Irganox 1726 and 0.5-1 g of cationic photoinitiator CPI200K (50% solution in propylene carbonate). The solvent was then removed under reduced pressure at 120°C to yield the acrylic copolymer. The weight-average molecular weight of the acrylic polymer was 175,000 Da (GPC), and the hot-melt viscosity (Brookfield, S27) of the polymer was approximately 75,000 mPa at 120°C. * It is s.

[0052] Example 6: Coating and curing of acrylic copolymer The acrylic copolymer is coated using a lab coater capable of heating both rolls to 120-130°C. Prior to this, the polymer is preheated in an oven to 120°C. The adhesive is coated to a thickness of 80 μm onto a 50 μm thick silicone release liner. After coating, the adhesive is illuminated with a 365 nm LED at 1,500 mJ / cm. 2 The adhesive film is laminated with an etched polyethylene terephthalate (PET) foil (50 μm) and conditioned at 23° C. and 50% relative humidity for 24 hours.

[0053] <Example 7: Peel measurement of adhesive film> After conditioning, the cured adhesive film was cut into three test strips measuring 25 mm x 150 mm. A stainless steel plate (Rocholl) was cleaned with ethyl acetate and acetone and dried for 30 minutes at 23°C and 50% relative humidity. The backing paper from the adhesive test strips was removed, and the strips were placed along the stainless steel plate. All samples were rolled twice in each direction with a 2 kg FINAT roller at a speed of 10 mm / s. The test strips were then conditioned for 20 minutes at 23°C and 50% relative humidity. A ZWICK tensile tester was set to a speed of 300 mm / min, and the free end of the tape was inserted into the upper jaw. A steel plate was clamped in the lower jaw, and the strips were peeled from the steel substrate at a 180° angle according to AFERA ​​4001 / DIN EN ISO 11339:2010-06.

[0054] Example 8: Shear Adhesion Failure Test (SAFT) For this test, three strips measuring 25mm x 70mm were cut from the cured and conditioned adhesive. SAFT steel plate samples were cleaned with ethyl acetate and acetone and conditioned for 30 minutes at 23°C and 50% relative humidity. The backing paper from the test strips was removed, and the strips were placed on the 25mm x 25mm square test area of ​​the steel plate. All strips were rolled twice in each direction with a 2kg FINAT roller at a speed of 10mm / s. After rolling, a test hook was secured to the test strip, and all samples were conditioned for an additional 30 minutes at 23°C and 50% relative humidity. The samples were then placed in a test oven, a 1kg weight was attached to the hook, and the oven was heated to 200°C at a ramp rate of 0.5°C / min. The test method conformed to GTF 6001 (Afera 5013).

[0055] Example 9: Preparation of acrylic adhesive A 1 L four-neck round-bottom polymerization flask was equipped with a thermometer connected to a temperature controller, a condenser, an overhead mechanical stirrer, two addition funnels, and a nitrogen inlet / outlet. The setup was purged with nitrogen gas for 15 minutes. The following monomer mixture was prepared: butyl acrylate (148.8 g) and 1-acrylomethyl-3,4-cyclohexene epoxide (1.2 g). 112 g of the monomer mixture was added to one funnel. Another funnel was charged with initiator 2,2'-azobis-(2-methylpropionitrile) (AIBN, 0.1 g), isopropanol (15 g), and ethyl acetate (45 mL). The remaining monomer mixture (38 g), initiator AIBN (0.2 g), isopropanol (6 mL), and ethyl acetate (34 mL) were added to the polymerization flask. The mixture was heated to a vigorous reflux and held for 15 minutes. Next, the monomer mixture in the funnel was added continuously at a constant rate over two hours. Simultaneously, the initiator solution in the funnel was added continuously at a constant rate over three hours. After the initiator solution addition was complete, the mixture was stirred at reflux for an additional two hours. A short-life initiator (0.75 g) and ethyl acetate (25 mL) were added to the initiator funnel and then added to the polymerization flask over one hour to reduce residual monomer. After the ethyl acetate was removed under vacuum at 55-60°C, an acrylic adhesive was obtained with a weight-average molecular weight (Mw) of 58,000 g / mol, a PDI (by GPC) of 2.6, and a Brookfield viscosity at 60°C of 130,000 cps, as disclosed herein.

[0056] Example 10: Coating and curing of acrylic copolymer The acrylic polymer of Example 9 (65 g) was mixed with ITX (0.5 g), OMNICAT 320 (0.5 g), the reactive diluent epoxidized soybean oil NATUREFLEXX ESO (25 g), and the tackifier TECKROS R86 (10 g). The mixture was cured with an LED 365 nm lamp. The adhesive film was 1 mil thick and applied directly onto 2 mil PET, providing 600 mJ / cm. 2The adhesive was cured with a 365 nm LED at a dose of 1000 rpm and shear tested on a stainless steel panel. Although the acrylic polymer obtained in Example 9 has a viscosity of approximately 130,000 cps at 60°C, the adhesive application temperature could be reduced to below 60°C.

Claims

1. a. Acrylic epoxy copolymer; b. At least one sulfonium salt-based photoinitiator, and c. At least one thioxanthone-based photosensitizer A UV-LED curable hot melt pressure-sensitive adhesive composition containing [the specified ingredient].

2. The adhesive composition according to claim 1, characterized in that the acrylic-epoxy copolymer is prepared from a monomer acrylic mixture copolymerized with an alicyclic epoxide.

3. Acrylic mixtures have a general structure (I): 【Chemistry 1】 [In the formula, R １ is C1-C18 alkyl, or H, R ２ is H or CH ３ And, R ３ is H or CH ３ And, n is an integer between 0 and 18. The adhesive composition according to claim 2, characterized by comprising at least one aliphatic acrylic monomer.

4. The adhesive composition according to claim 3, characterized in that the monomer acrylic mixture comprises at least one acrylate selected from the group consisting of methyl acrylate, ethyl acrylate, and isobutyl acrylate, and at least one acrylic monomer selected from the group consisting of 2-ethylhexyl acrylate, n-butyl acrylate, 2-propylheptyl acrylate, and isodecyl acrylate.

5. General structure (III): 【Chemistry 2】 [In the formula, R １ is C1-C18 alkyl or H, R ２ is C1-C18 alkyl or C1-C18 alkoxy, R ３ [is an alicyclic epoxy or epoxy group] The adhesive composition according to claim 2, characterized in that epoxy acrylic monomers are copolymerized.

6. The adhesive composition according to claim 2, wherein the acrylic-epoxy copolymer is preferably obtained by solution polymerization in a solvent selected from the group consisting of ethyl acetate, butanone, heptane, hexane, pentanone, acetone, toluene, propyl acetate, benzene, and mixtures thereof.

7. At least one sulfonium salt-based photoinitiator is defined by general formula (III): 【Transformation 3】 [In the formula, R １ is selected from H, aryl, thioaryl, C1-C18 alkyl, C1-C18 alkoxy, SH or NR ２ and R ２ is selected from P, Sb, B, As, or Bi, R ３ is, F ６－ or F ３ (C ２ F ５ ) ３－ [is] The adhesive composition according to claim 1, characterized by being represented as follows.

8. At least one thioxanthone photosensitizer is defined by general formula (IV): 【Chemistry 4】 [In the formula, R １ NH, CH ２ , S or O, R ２ ~R ９ These are independently H, C1-C18 alkyl or isoalkyl, C1-C18 alkoxy, aryl, COOH, OH, NR ２ [COOR, urea, urethane, S or SH] The adhesive composition according to claim 1, characterized by being represented as follows.

9. The adhesive composition according to claim 1, wherein the application temperature of the adhesive composition is 60 to 150°C, preferably 100 to 130°C, and more preferably 110 to 120°C.

10. The adhesive composition was measured by UV radiation measurement (Puk measurement, in this case, EIT Power Puk II) and showed a reading of 100 to 10,000 mJ / cm². ２ Preferably 300 to 3,000 mJ / cm² ２ The adhesive composition according to claim 1, characterized in that it can be cured at a UVA dose.

11. The adhesive composition according to claim 1, characterized in that the cured adhesive has a shear adhesion failure temperature (SAFT) of 50 to 200°C, preferably 120 to 200°C, as measured according to GTF 6001 (Afera 5013).

12. The adhesive composition according to claim 1, characterized in that the cured adhesive exhibits a performance of 2 to 45 N / 25 mm, preferably 5 to 35 N / 25 mm, at 300 mm / min in a 180° peel on a steel substrate as measured in accordance with DIN ES ISO 11339 / 2010-06.

13. A method for producing an adhesive composition according to any one of claims 1 to 12, comprising copolymerizing an acrylic monomer mixture with an alicyclic epoxide, and blending the resulting acrylic-epoxy-polymer with at least one sulfonium salt-based photoinitiator and at least one thioxanthone-based photosensitizer to obtain an adhesive composition.

14. The method according to claim 13, wherein the copolymerization is carried out in a solvent selected from the group consisting of ethyl acetate, butanone, heptane, hexane, pentanone, acetone, toluene, propyl acetate, benzene, and mixtures thereof.

15. An article comprising a first substrate and a second substrate bonded together with an adhesive composition according to any one of claims 1 to 12.

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