Dual-cure semi-structural adhesive composition and method for preparing same

Abstract

The present invention provides a dual-cure semi-structural adhesive composition and a method for preparing the same. Specifically, the dual-cure semi-structural adhesive composition comprises an acrylic copolymer containing acryloxybenzophenone copolymerized units and epoxidized acrylic copolymerized units, an epoxy resin, a polyol, and a cationic photoinitiator. When the dual-cure semi-structural adhesive composition according to the technical solution of the present invention is used to bond adherends, the dual-cure semi-structural adhesive composition can immediately exhibit strong initial tack after primary curing with ultraviolet light, thereby preventing warping and slippage of the adherend, and can further provide reliable final cured adhesion strength after subsequent cationic secondary curing.

Description

[Technical Field]

[0001] The present invention relates to the field of structural adhesives, and in particular to a dual cure semi-structural adhesive composition and method for its preparation. [Background technology]

[0002] In certain applications, UV-initiated semi-structural adhesives can provide high adhesive strength comparable to that of liquid structural adhesives. However, the curing process of currently used UV-initiated semi-structural adhesives is generally slow, requiring several hours to achieve basic cohesive strength. This can lead to problems with adherends warping or slipping after bonding. In practical applications, additional measures such as pressure or clamps are required after applying the semi-structural adhesive to prevent the adherends from warping or slipping during the curing process.

[0003] Therefore, it is extremely important to develop a semi-structural adhesive that can immediately develop sufficient initial adhesion when applied to an adherend and provide strong adhesion after final curing. Summary of the Invention

[0004] Based on the above technical problems, an object of the present invention is to provide a dual-cure semi-structural adhesive composition and a method for preparing the same. The dual-cure semi-structural adhesive composition is capable of immediately developing strong initial adhesive strength when used to bond adherends, thereby preventing warping and slippage of the adherends, and is capable of developing reliable final cured adhesive strength through subsequent secondary curing.

[0005] The inventors have conducted intensive and detailed research to perfect the present invention.

[0006] According to one aspect of the present invention, a dual-cure semi-structural adhesive composition is provided, the composition comprising an acrylic copolymer comprising acryloxybenzophenone copolymerized units and epoxidized acrylic copolymerized units, an epoxy resin, a polyol, and a cationic photoinitiator.

[0007] According to another aspect of the present invention, there is provided a method for preparing the dual-cure semi-structural adhesive composition, which comprises uniformly mixing the components of the dual-cure semi-structural adhesive composition.

[0008] Compared to existing technologies in the art, the present invention has the following advantages: when used to bond adherends, the dual-cure semi-structural adhesive composition can immediately develop strong initial adhesive strength through primary curing with ultraviolet light, thereby preventing warping and slippage of the adherend, and can further provide reliable final cured adhesive strength through subsequent cationic secondary curing. DETAILED DESCRIPTION OF THE INVENTION

[0009] It should be understood that various other embodiments may be devised or modified by those skilled in the art based on the disclosure herein, without departing from the scope or spirit of the present disclosure. Accordingly, the specific embodiments set forth below are not intended to be limiting in this sense.

[0010] Unless otherwise expressly stated, all numerical values ​​used in this specification and claims regarding dimensions, amounts, and specific physicochemical properties should be construed as being modified by the word "approximately." Thus, unless otherwise specified, average values ​​for numerical parameters set forth in this specification and the appended claims are approximations that may be appropriately modified by one of ordinary skill in the art using the knowledge disclosed herein to obtain desired properties. The use of numerical ranges stated by endpoints includes all numbers within that range and any range within that range; for example, "1 to 5" includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.

[0011] Currently, those skilled in the art desire to develop a semi-structural adhesive that immediately develops sufficient initial tack when applied to an adherend and exhibits strong adhesion after final curing. During their research, the inventors of the present invention discovered that the above technical problems could be solved by using an acrylic copolymer with a specific structure in the semi-structural adhesive. The acrylic copolymer simultaneously contains: copolymerized units capable of initiating a crosslinking reaction with ultraviolet light (which immediately improves the cohesive strength of the semi-structural adhesive after ultraviolet light irradiation and prevents warping or slippage of the adherend after bonding); and cationic crosslinkable copolymerized units (which can polymerize with epoxy resins through a cationic reaction and provide high adhesive strength after final curing).

[0012] Specifically, according to one aspect of the present invention, there is provided a dual-cure semi-structural adhesive composition comprising an acrylic copolymer including acryloxybenzophenone copolymerized units and epoxidized acrylic copolymerized units, an epoxy resin, a polyol, and a cationic photoinitiator.

[0013] According to the technical solution of the present invention, a dual-cure semi-structural adhesive composition comprises an acrylic copolymer, which comprises acryloxybenzophenone copolymerized units and epoxidized acrylic copolymerized units. During the application process of the dual-cure semi-structural adhesive composition, the acryloxybenzophenone copolymerized units can abstract active hydrogen from the system through ultraviolet irradiation, thereby initiating pre-crosslinking through a free radical reaction. This pre-crosslinking can increase the cohesive strength of the semi-structural adhesive immediately after ultraviolet irradiation, thereby preventing warping and slippage of the adherend after bonding. Furthermore, the epoxidized acrylic copolymerized units can polymerize with the epoxy resin through a cationic reaction in the subsequent curing process, thereby providing high adhesive strength after final curing.

[0014] There are no particular restrictions on the number average molecular weight of the acrylic copolymer. Preferably, the number average molecular weight of the acrylic copolymer is in the range of 500,000 to 800,000. When the number average molecular weight of the acrylic copolymer is selected from the range of 500,000 to 800,000, the resulting dual-cure semi-structural adhesive composition has good film-forming properties, and at the same time, the acrylic copolymer, epoxy resin, and polyol have good compatibility among themselves.

[0015] Preferably, the comonomer forming the acryloxybenzophenone copolymerized units is one or more selected from 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxybutoxybenzophenone, etc. According to a specific preferred embodiment of the present invention, the acryloxybenzophenone copolymerized units account for 0.05 to 1 wt %, preferably 0.5 to 1 wt %, of an acrylic copolymer having a total weight of 100 wt %. The acryloxybenzophenone copolymerized units are copolymerized into the polymer segments of the acrylic copolymer and remain stable until excited by ultraviolet light. Compared to epoxidized acrylic copolymerized units, the acryloxybenzophenone copolymerized units are instantly crosslinked after excitation by ultraviolet light, which improves the degree of crosslinking and average molecular weight of the entire adhesive and improves the cohesiveness and warp resistance of the adhesive during initial curing. If the content of acryloxybenzophenone copolymerized units in the acrylic copolymer is too high, the free radical crosslink density of the adhesive will be too high, resulting in poor wetting of the substrate and a low overall peel strength of the adhesive after the subsequent cationic crosslinking reaction is complete.

[0016] Preferably, the comonomer forming the epoxidized acrylic copolymerized units is one or more selected from glycidyl methacrylate, oxetane methacrylate, etc. According to a specific preferred embodiment of the present invention, the epoxidized acrylic copolymerized units account for 3 to 15 wt% of the acrylic copolymer, with the total weight being 100 wt%. The inventors have found that if the proportion of the epoxidized acrylic copolymerized units in the acrylic copolymer is too small, the epoxidized acrylic copolymerized units cannot exhibit the toughness-improving effect achieved by copolymerization with the epoxy resin, and if the proportion of the epoxidized acrylic copolymerized units is too large, the crosslink density becomes high, adversely affecting the final peel strength of the adhesive.

[0017] The acrylic copolymer further contains acrylate copolymerized units other than the acryloxybenzophenone copolymerized units and the epoxidized acrylic copolymerized units.

[0018] Preferably, the acrylate copolymerized units other than the acryloxybenzophenone copolymerized units and the epoxidized acrylic copolymerized units include: high Tg (glass transition temperature) acrylate copolymerized units, wherein the homopolymer of the acrylate comonomer that forms the high Tg acrylate copolymerized units has a Tg of greater than 20°C; and low Tg (glass transition temperature) acrylate copolymerized units, wherein the homopolymer of the acrylate comonomer that forms the low Tg acrylate copolymerized units has a Tg of less than 0°C.

[0019] Preferably, the acrylate comonomer forming the high Tg acrylate copolymerized unit is one or more selected from butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Furthermore, the acrylate comonomer forming the low Tg acrylate copolymerized unit is one or more selected from methyl (meth)acrylate, isobornyl (meth)acrylate, (meth)acrylic acid, and acrylamide.

[0020] Preferably, the glass transition temperature of the acrylic copolymer is in the range of −15° C. to 0° C. According to the technical solution of the present invention, by adjusting the ratio of high Tg acrylate copolymerized units to low Tg acrylate copolymerized units, the glass transition temperature of the resulting acrylic copolymer can be controlled within the above range, thereby achieving good mechanical properties of the resulting dual-cure semi-structural adhesive composition.

[0021] According to the technical solution of the present invention, the dual cure semi-structural adhesive composition preferably contains 40 to 65 wt % of an acrylic copolymer, when the total weight of the dual cure semi-structural adhesive composition is 100 wt %.

[0022] In addition to the acrylic copolymer described above, the dual-cure semi-structural adhesive composition of the present invention further contains an epoxy resin. The epoxy resin is copolymerized with the epoxidized acrylic copolymerized units in a cationic polymerization process to achieve strong final cured adhesion of the structural adhesive composition. The specific type of epoxy resin that can be used in the present invention is not particularly limited and can be appropriately selected from conventional epoxy resin materials commonly used in the field of structural adhesives. Preferably, the epoxy resin is a liquid epoxy resin or a semi-solid epoxy resin. The epoxy equivalent of the epoxy resin is preferably in the range of 76 to 500 eq / 100 g. Commercially available and economical epoxy resin products such as bisphenol A epoxy resin and bisphenol F epoxy resin can be used. Ester ring-type epoxy resins, such as glycidyl ethers obtained by reacting polyphenols such as hydrogenated bisphenol A, tetramethylbisphenol A, diarylbisphenol A, and tetramethylbisphenol F with epichlorohydrin, as well as epoxidized polyolefins and other known epoxy resins can also be used.

[0023] Preferably, the dual-cure semi-structural adhesive composition contains 30 to 50 wt % of epoxy resin, assuming the total weight of the dual-cure semi-structural adhesive composition to be 100 wt %. The inventors of the present application have found that the amount of epoxy resin is primarily related to the cohesive strength, such as shear strength, of the adhesive after curing. If the amount of epoxy resin is too small, the shear strength of the adhesive after curing will be insufficient. If the amount of epoxy resin is too large, it will affect the film-forming stability of the adhesive before curing, making the adhesive after curing excessively brittle and reducing peel strength.

[0024] In addition to the acrylic copolymer and epoxy resin described above, the dual-cure semi-structural adhesive composition according to the present invention further contains a polyol. The polyol is a compound containing two or more hydroxyl groups. Preferably, the polyol is a polyether polyol. More preferably, the polyol is a polyether diol, polyether triol, or the like. Preferably, the weight-average molecular weight of the polyol is in the range of 500 to 3,000 g / mol. When the weight-average molecular weight of the polyol is selected within the range of 500 to 3,000 g / mol, the components, such as the acrylic copolymer, the epoxy resin, and the polyol, exhibit good compatibility and reactivity with each other.

[0025] Commercially available examples of polyols that can be used in the present invention include TONE 0230 Polyol, VORANOL 230-238, and Varonol 2070 manufactured by Dow Chemical Company (USA), and Dianol 285 manufactured by Seppic (France). In a particularly preferred embodiment, Varonol 2070, a 700 molecular weight polyether triol manufactured by Dow Chemical Company (USA), is used.

[0026] Preferably, the dual-cure semi-structural adhesive composition contains 3 to 12 wt % of a polyol, where the total weight of the dual-cure semi-structural adhesive composition is taken as 100 wt %. The polyol functions to adjust the rate of photoinduced cationic polymerization in the dual-cure semi-structural adhesive composition, and is copolymerized into the crosslinked epoxy group network to adjust the curing flexibility of the composition. If the polyol content is too low, the curing rate will be fast, but the adhesive will become brittle and the peel strength will decrease. If the polyol content is too high, the film-forming stability of the adhesive before curing will be poor, the curing rate will be slow, and the adhesive will become excessively soft, adversely affecting shear strength.

[0027] In addition to the acrylic copolymer, epoxy resin, and polyol described above, the dual-cure semi-structural adhesive composition of the present invention further contains a cationic photoinitiator. The specific type of cationic photoinitiator usable in the present invention is not particularly limited, and can be appropriately selected from conventional cationic photoinitiators generally used to initiate the cationic polymerization of epoxy compounds. Preferably, the cationic photoinitiator is one or more selected from diazonium salts, iodonium salts, sulfonium salts, antimonates, and iron arenes. Specific examples of cationic photoinitiators include triarylhexafluoroantimonates, diaryliodonium salts, arylsulfonium salts, alkylsulfonium salts, iron arene salts, sulfonyloxyketones, and triarylsiloxanes. Triarylhexafluoroantimonates (product name: Doublecure 1176) manufactured by Double Bond Chemical Co., Ltd., Taiwan, can also be used.

[0028] According to a specific embodiment of the present invention, the dual-cure semi-structural adhesive composition contains 0.02 to 3 wt %, preferably 0.5 to 2.5 wt %, of a cationic photoinitiator, based on 100 wt % of the total weight of the dual-cure semi-structural adhesive composition. If the cationic photoinitiator content is too low, the reaction rate will be slow and the curing process will be susceptible to moisture inhibition, resulting in incomplete final cure. If the cationic photoinitiator content is too high, the curing rate will be too fast and the crosslinked network structure will become brittle.

[0029] According to another aspect of the present invention, there is provided a method for preparing a dual-cure semi-structural adhesive composition, the method comprising uniformly mixing the components of the dual-cure semi-structural adhesive composition described above. No special processing steps are required for mixing, and mixing can be performed manually or mechanically at room temperature.

[0030] The following detailed description is illustrative of the disclosure but not limiting of the disclosure.

[0031] Embodiment 1 is a dual-cure semi-structural adhesive composition that includes an acrylic copolymer including acryloxybenzophenone copolymerized units and epoxidized acrylic copolymerized units, an epoxy resin, a polyol, and a cationic photoinitiator.

[0032] Embodiment 2 is the dual-cure semi-structural adhesive composition described in Embodiment 1, wherein the comonomer forming the acryloxybenzophenone copolymerized unit is one or more selected from 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, and 4-acryloyloxybutoxybenzophenone.

[0033] Embodiment 3 is a dual-cure semi-structural adhesive composition according to embodiment 1, in which the acryloxybenzophenone copolymerization units account for 0.05 to 1 wt % of the acrylic copolymer having a total weight of 100 wt %.

[0034] Embodiment 4 is a dual-cure semi-structural adhesive composition according to embodiment 1, in which the acryloxybenzophenone copolymerized units account for 0.5 to 1 wt % of the acrylic copolymer having a total weight of 100 wt %.

[0035] Embodiment 5 is a dual-cure semi-structural adhesive composition according to embodiment 1, wherein the comonomer forming the epoxidized acrylic copolymerized unit is one or more selected from the group consisting of glycidyl methacrylate and oxetane methacrylate.

[0036] Embodiment 6 is the dual-cure semi-structural adhesive composition according to embodiment 1, wherein the epoxidized acrylic copolymerized units account for 3 to 15 wt % of the acrylic copolymer having a total weight of 100 wt %.

[0037] Embodiment 7 is the adhesive composition of embodiment 1, wherein the acrylic copolymer further comprises acrylate copolymerized units other than the acryloxybenzophenone copolymerized units and the epoxidized acrylic copolymerized units.

[0038] Embodiment 8 is the dual-cure semi-structural adhesive composition of embodiment 1, wherein the acrylate copolymerized units other than the acryloxybenzophenone copolymerized units and the epoxidized acrylic copolymerized units comprise: a high Tg acrylate copolymerized unit, wherein the homopolymer of the acrylate comonomer forming the high Tg acrylate copolymerized unit has a Tg greater than 20°C; and A low Tg acrylate copolymerized unit, wherein the Tg of the homopolymer of the acrylate comonomer forming the low Tg acrylate copolymerized unit is lower than 0°C.

[0039] Embodiment 9 is a dual-cure semi-structural adhesive composition according to embodiment 8, wherein the acrylate comonomer forming the high Tg acrylate copolymerized unit is one or more selected from the group consisting of butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0040] Embodiment 10 is a dual-cure semi-structural adhesive composition according to embodiment 8, wherein the acrylate comonomer forming the low Tg acrylate copolymerized unit is one or more selected from methyl (meth)acrylate, isobornyl (meth)acrylate, (meth)acrylic acid, and acrylamide.

[0041] Embodiment 11 is a dual-cure semi-structural adhesive composition according to embodiment 1, which contains 40 to 65% by weight of an acrylic copolymer when the total weight of the composition is 100% by weight.

[0042] Embodiment 12 is the dual-cure semi-structural adhesive composition according to embodiment 1, wherein the epoxy resin is a liquid epoxy resin or a semi-solid epoxy resin.

[0043] Embodiment 13 is the dual-cure semi-structural adhesive composition according to Embodiment 1, in which the epoxy resin has an epoxy equivalent weight in the range of 76 to 500 eq / 100 g.

[0044] Embodiment 14 is the dual-cure semi-structural adhesive composition according to embodiment 1, which contains 30 to 50% by weight of an epoxy resin when the total weight of the composition is 100% by weight.

[0045] Embodiment 15 is the dual-cure semi-structural adhesive composition of embodiment 1, wherein the polyol is a compound containing two or more hydroxyl groups.

[0046] Embodiment 16 is the dual-cure semi-structural adhesive composition of embodiment 1, wherein the polyol is a polyether polyol.

[0047] Embodiment 17 is the dual-cure semi-structural adhesive composition of embodiment 1, wherein the polyol is a polyether diol or polyether triol.

[0048] Embodiment 18 is the dual-cure semi-structural adhesive composition according to embodiment 1, wherein the weight-average molecular weight of the polyol is in the range of 500 to 3000 g / mol.

[0049] Embodiment 19 is the dual-cure semi-structural adhesive composition according to embodiment 1, which contains 3 to 12 wt % of polyol when the total weight of the composition is 100 wt %.

[0050] Embodiment 20 is the dual-cure semi-structural adhesive composition of embodiment 1, wherein the cationic photoinitiator is one or more selected from diazonium salts, iodonium salts, sulfonium salts, antimonates, and iron arenes.

[0051] Embodiment 21 is the dual-cure semi-structural adhesive composition described in Embodiment 1, and Embodiment 2 is the dual-cure semi-structural adhesive composition described in Embodiment 1.

[0052] Embodiment 22 is a method for preparing a dual-cure semi-structural adhesive composition, comprising uniformly mixing the components of the dual-cure semi-structural adhesive composition described in any one of embodiments 1 to 21.

[0053] The present invention will be described in more detail based on the following examples. However, these descriptions and examples are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the appended claims. [Example]

[0054] In the present invention, unless otherwise specified, all reagents used are commercially available products and were used as they were without further purification. In addition, in the present invention, "%" means "% by weight" unless otherwise specified. [Table 1]

[0055] <Test Method> [Warp prevention] In the present invention, the warpage resistance of an adhesive film was evaluated by the 1-minute shear strength of the adhesive film using the GB / T 7124-2008 method. The 1-minute shear strength here refers to the shear strength of the adhesive film measured 1 minute after the adhesive film was attached to the substrate. Specifically, the release layer of the adhesive tape prepared in the following Examples or Comparative Examples was peeled off, and the adhesive film was attached to an aluminum plate (dimensions: 1 inch x 4 inches). Next, a glass plate (dimensions: 1 inch x 4 inches x 1 mm thick) was shifted and laminated to the side of the aluminum plate to which the adhesive film was attached, so that the overlapping area of ​​the laminated structure consisting of aluminum plate / adhesive film / glass plate was 1 inch x 1 / 2 inch. Next, the adhesive film sandwiched between the aluminum plate and the glass plate was irradiated with 3000 mJ / cm using a UVATA 365 nm LED UV curing machine. 2 After 1 minute of UV irradiation, the shear strength was immediately measured using the GB / T 7124-2008 method.

[0056] If the measured 1-minute shear strength is 0.2 MPa or greater, the adhesive film will not warp or slip on the adherend during use and may be readily handled during manufacturing and assembly. If the measured 1-minute shear strength is 0.3 MPa or greater, the adhesive film is deemed to have excellent warp resistance. If the measured 1-minute shear strength is less than 0.2 MPa, the adhesive film is deemed to warp or slip on the adherend during use.

[0057] [180° peel strength after final curing] In the present invention, the 180° peel strength, which is one of the adhesive properties of the adhesive film after final curing, was evaluated according to the ASTM D3300 method. Specifically, the adhesive composition prepared in the following Examples or Comparative Examples was coated onto a 100 μm thick polyethylene terephthalate film (PET film) using a comma bar coater so that the adhesive film was 35 μm thick. Next, the adhesive film (1 / 2 inch x 6 inch) was cured with 3000 mJ / cm using a UVATA 365 nm LED UV curing machine. 2 The adhesive film was then applied to an aluminum plate (dimensions: 2 inches x 4 inches) within 1 minute. The resulting laminate was then cured at 80°C for 1 hour. Finally, the 180° peel strength was measured according to ASTM D3300 method.

[0058] If the 180° peel strength measured after final cure was 0.4 N / mm or greater, the adhesive film was judged to have reliable final cure adhesion. If the 180° peel strength measured after final cure was 0.6 N / mm or greater, the final cure adhesion was judged to be excellent. If the 180° peel strength measured after final cure was less than 0.4 N / mm, the final cure adhesion was judged to not meet practical adhesion requirements.

[0059] [Shear strength after final hardening] In the present invention, the shear strength, which is one of the adhesive properties of the adhesive film after final curing, was evaluated using the GB / T 7124-2008 method. Specifically, the adhesive composition prepared in the following examples or comparative examples was coated onto a 50 μm thick polyethylene terephthalate film (PET film) using a comma bar coater so that the adhesive film was 100 μm thick. Next, the adhesive film (1 inch x 1 inch) was irradiated with 3000 mJ / cm using a UVATA 365 nm LED UV curing machine. 2The adhesive film was irradiated with ultraviolet energy of 1000 kJ / cm², the PET film was peeled off, and the irradiated adhesive film was attached to an aluminum plate (dimensions: 1 inch x 4 inches) within 1 minute. The resulting adhesive film / aluminum plate laminate was then cured at 80°C for 1 hour. Next, an approximately 200 μm thick epoxy structural adhesive (DP100, manufactured by 3M) and an aluminum plate (dimensions: 1 inch x 4 inches) were placed on the adhesive film side of the laminate, resulting in a laminate structure consisting of aluminum plate / adhesive film / epoxy structural adhesive / aluminum plate. At this time, the overlap area of ​​the two aluminum plates facing each other was 1 inch x 1 / 2 inch. The laminate was then cured at 80°C for an additional 2 hours. Finally, the shear strength was measured using the GB / T 7124-2008 method.

[0060] If the shear strength measured after final curing is 5 MPa or greater, the adhesive film is judged to be able to achieve a reliable final cured adhesion. If the shear strength measured after final curing is 7 MPa or greater, the adhesive film is judged to have excellent adhesion after final curing. If the shear strength measured after final curing is less than 5 MPa, the adhesive film is judged to have insufficient adhesion to meet practical adhesive requirements.

[0061] Preparation Example 1 (Preparation of Acrylic Copolymer 1 (55% BA / 29% MA / 8% 2-HEA / 8% GMA)) 100 g of acrylic monomers (including 55 g of butyl acrylate (BA), 29 g of methyl acrylate (MA), 8 g of 2-hydroxyethyl acrylate (2-HEA), and 8 g of glycidyl methacrylate (GMA)), 150 g of ethyl acetate, and 0.2 g of Vazo 67 initiator (BASF) were added to a 500 mL three-neck flask according to the above weight ratio. The mixture was heated to 60°C using an air-operated stirrer (ZD-J-1 type, Shanghai Zuoda Coating Equipment Co., Ltd.) at 100-150 rpm. The reaction was continued for 24 hours, yielding a viscous acrylic copolymer solution with a solids content of 40%. The acrylic copolymer was then separated as a solid from the acrylic copolymer solution for further use.

[0062] Preparation Example 2 (Preparation of Acrylic Copolymer 2 (55% BA / 29% MA / 8% 2-HEA / 8% GMA / 1% ABP)) 101 g of acrylic monomers (including 55 g of butyl acrylate (BA), 29 g of methyl acrylate (MA), 8 g of 2-hydroxyethyl acrylate (2-HEA), 8 g of glycidyl methacrylate (GMA), and 1 g of 4-acryloyloxybenzophenone (ABP)), 150 g of ethyl acetate, and 0.2 g of Vazo 67 initiator (BASF) were added to a 500 mL three-neck flask according to the above weight ratio. The mixture was heated to 60°C using an air-operated stirrer (ZD-J-1 type, Shanghai Zuoda Coating Equipment Co., Ltd.) at 100-150 rpm. The reaction was continued for 24 hours, yielding a viscous acrylic copolymer solution with a solids content of 40%. The acrylic copolymer was then separated as a solid from the acrylic copolymer solution for further use.

[0063] Preparation Example 3 (Preparation of Acrylic Copolymer 3 (55% BA / 29% MA / 8% 2-HEA / 8% GMA / 0.5% ABP)) 100.5 g of acrylic monomers (including 55 g of butyl acrylate (BA), 29 g of methyl acrylate (MA), 8 g of 2-hydroxyethyl acrylate (2-HEA), 8 g of glycidyl methacrylate (GMA), and 0.5 g of 4-acryloyloxybenzophenone (ABP)), 150 g of ethyl acetate, and 0.2 g of Vazo 67 initiator (BASF) were added to a 500 mL three-neck flask according to the above weight ratio. The mixture was heated to 60°C using an air-operated stirrer (ZD-J-1 type, Shanghai Zuoda Coating Equipment Co., Ltd.) at 100-150 rpm. The reaction was continued for 24 hours, yielding a viscous acrylic copolymer solution with a solids content of 40%. The acrylic copolymer was then separated as a solid from the acrylic copolymer solution for further use.

[0064] Preparation Example 4 (Preparation of Acrylic Copolymer 4 (55% BA / 29% MA / 8% 2-HEA / 8% GMA / 0.05% ABP)) 100.05 g of acrylic monomers (including 55 g of butyl acrylate (BA), 29 g of methyl acrylate (MA), 8 g of 2-hydroxyethyl acrylate (2-HEA), 8 g of glycidyl methacrylate (GMA), and 0.05 g of 4-acryloyloxybenzophenone (ABP)), 150 g of ethyl acetate, and 0.2 g of Vazo 67 initiator (BASF) were added to a 500 mL three-neck flask according to the above mass ratio. The mixture was heated to 60°C using an air-operated stirrer (ZD-J-1 type, Shanghai Zuoda Coating Equipment Co., Ltd.) at 100-150 rpm. The reaction was continued for 24 hours, yielding a viscous acrylic copolymer solution with a solids content of 40%. The acrylic copolymer was then separated as a solid from the acrylic copolymer solution for further use.

[0065] Preparation Example 5 (Preparation of Acrylic Copolymer 5 (57% BA / 29.5% MA / 8% 2-HEA / 3% GMA / 0.5% ABP)) 98 g of acrylic monomers (including 57 g of butyl acrylate (BA), 29.5 g of methyl acrylate (MA), 8 g of 2-hydroxyethyl acrylate (2-HEA), 3 g of glycidyl methacrylate (GMA), and 0.5 g of 4-acryloyloxybenzophenone (ABP)), 150 g of ethyl acetate, and 0.2 g of Vazo 67 initiator (BASF) were added to a 500 mL three-neck flask according to the above mass ratio. The mixture was heated to 60°C using an air-operated stirrer (ZD-J-1 type, Shanghai Zuoda Coating Equipment Co., Ltd.) at 100-150 rpm. The reaction was continued for 24 hours, yielding a viscous acrylic copolymer solution with a solids content of 40%. The acrylic copolymer was then separated as a solid from the acrylic copolymer solution for further use.

[0066] Preparation Example 6 (Preparation of Acrylic Copolymer 6 (51% BA / 25.5% MA / 8% 2-HEA / 15% GMA / 0.5% ABP)) 100 g of acrylic monomers (including 51 g of butyl acrylate (BA), 25.5 g of methyl acrylate (MA), 8 g of 2-hydroxyethyl acrylate (2-HEA), 15 g of glycidyl methacrylate (GMA), and 0.5 g of 4-acryloyloxybenzophenone (ABP)), 150 g of ethyl acetate, and 0.2 g of Vazo 67 initiator (BASF) were added to a 500 mL three-neck flask according to the above weight ratio. The mixture was heated to 60°C using an air-operated stirrer (ZD-J-1 type, Shanghai Zuoda Coating Equipment Co., Ltd.) at 100-150 rpm. The reaction was continued for 24 hours, yielding a viscous acrylic copolymer solution with a solids content of 40%. The acrylic copolymer was then separated as a solid from the acrylic copolymer solution for further use.

[0067] [Example 1] Adhesive composition 1 was prepared by uniformly mixing 45 g of the acrylic copolymer 2 prepared above, 40 g of epoxy resin NPES 128, 5 g of epoxy resin NPES 901, 8 g of polyol Varonol 2070, and 2 g of cationic photoinitiator Doublecure 1176. The types of raw materials used in preparing adhesive composition 1 and their blending ranges are shown in Table 2 below. Adhesive composition 1 was applied to a PET film, and the solvent was dried to obtain adhesive composition tape 1.

[0068] The corresponding properties of the resulting adhesive composition 1 were tested according to the above-mentioned evaluation methods for warpage resistance, 180° peel strength after final cure, and shear strength after final cure, and the results are shown in Table 2 below.

[0069] [Examples 2 to 9 and Comparative Examples 1 and 2] Adhesive compositions were prepared in the same manner as in Example 1, except that the types and compositions of the raw materials for the adhesive compositions were changed as shown in Table 2 below.

[0070] The corresponding properties of the resulting adhesive compositions were tested according to the above-described evaluation methods for warp resistance, 180° peel strength after final cure, and shear strength after final cure, and the results are shown in Table 2 below. [Table 2]

[0071] As is clear from the results shown in Table 2 above, when dual-cure semi-structural adhesive compositions (e.g., Examples 1 to 9) were prepared within the scope of the present invention, the resulting dual-cure semi-structural adhesive compositions, when used to bond adherends, were able to immediately exhibit strong initial tack through primary curing with ultraviolet light, thereby preventing warping and slippage of the adherends, and were further able to provide reliable final cured adhesive strength through subsequent cationic secondary curing.

[0072] In another aspect, as is clear from the results of Comparative Example 1 shown in Table 2 above, when the acrylic copolymer did not contain acryloxybenzophenone copolymerization units, the structural adhesive was unable to immediately obtain sufficient cohesive strength upon exposure to ultraviolet light after application, resulting in warping and slippage of the adherend after adhesion.

[0073] As is clear from the results of Comparative Example 2 shown in Table 2 above, when the acrylic copolymer did not contain acryloxybenzophenone copolymerization units and ABP was used as an externally added initiator, crosslinking of the adhesive components after UV excitation could not be effectively induced, the average molecular weight of the adhesive could not be effectively increased, and the immediate shear strength at 1 minute could not be significantly increased.

[0074] While specific embodiments have been shown and described in the present invention, those skilled in the art will recognize that various alternative and / or equivalent embodiments may be used to substitute for the specific embodiments described. This application is intended to cover all adaptations or variations of the specific embodiments described in the present invention. Accordingly, the present invention is limited only by the claims and equivalents thereof.

[0075] It should be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the present invention, and such changes and modifications are intended to be included within the scope of the present invention as defined by the appended claims.

Claims

1. an acrylic copolymer comprising copolymerized acryloxybenzophenone units and copolymerized epoxidized acrylic units; Epoxy resin, A polyol, Cationic Photoinitiators A dual cure semi-structural adhesive composition comprising:

2. 2. The dual cure semi-structural adhesive composition according to claim 1, wherein the comonomer forming the acryloxybenzophenone copolymerized unit is one or more selected from the group consisting of 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, and 4-acryloyloxybutoxybenzophenone.

3. 2. The dual-cure semi-structural adhesive composition according to claim 1, wherein the acryloxybenzophenone copolymerized units account for 0.05 to 1 wt % in the acrylic copolymer having a total weight of 100 wt %.

4. 2. The dual-cure semi-structural adhesive composition according to claim 1, wherein the acryloxybenzophenone copolymerized units account for 0.5 to 1 wt % of the acrylic copolymer having a total weight of 100 wt %.

5. The dual-cure semi-structural adhesive composition according to claim 1, wherein the comonomer forming the epoxidized acrylic copolymerized unit is at least one selected from the group consisting of glycidyl methacrylate and oxetane methacrylate.

6. 2. The dual-cure semi-structural adhesive composition according to claim 1, wherein the epoxidized acrylic copolymerized units account for 3 to 15 wt % of the acrylic copolymer, with the total weight being 100 wt %.

7. The dual-cure semi-structural adhesive composition according to claim 1 , wherein the acrylic copolymer further comprises acrylate copolymerized units other than the acryloxybenzophenone copolymerized units and the epoxidized acrylic copolymerized units.

8. the acrylate copolymerized units other than the acryloxybenzophenone copolymerized units and the epoxidized acrylic copolymerized units, a high Tg acrylate copolymerized unit, wherein the homopolymer of the acrylate comonomer forming the high Tg acrylate copolymerized unit has a Tg greater than 20°C; and A low Tg acrylate copolymerization unit, wherein the Tg of the homopolymer of the acrylate comonomer forming the low Tg acrylate copolymerization unit is lower than 0°C. The dual cure semi-structural adhesive composition of claim 7, comprising:

9. The dual cure semi-structural adhesive composition according to claim 8, wherein the acrylate comonomer forming the high Tg acrylate copolymerized unit is one or more selected from the group consisting of butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

10. The dual cure semi-structural adhesive composition according to claim 8, wherein the acrylate comonomer forming the low Tg acrylate copolymerized unit is one or more selected from the group consisting of methyl (meth)acrylate, isobornyl (meth)acrylate, (meth)acrylic acid, and acrylamide.

11. The dual cure semi-structural adhesive composition according to claim 1, wherein the dual cure semi-structural adhesive composition comprises 40 to 65 wt% of the acrylic copolymer, based on a total weight of the dual cure semi-structural adhesive composition being 100 wt%.

12. The dual-cure semi-structural adhesive composition according to claim 1, wherein the epoxy resin is a liquid epoxy resin or a semi-solid epoxy resin.

13. 2. The dual-cure semi-structural adhesive composition according to claim 1, wherein the epoxy resin has an epoxy equivalent ranging from 76 to 500 eq / 100 g.

14. The dual cure semi-structural adhesive composition according to claim 1, wherein the dual cure semi-structural adhesive composition comprises 30 to 50 wt% of the epoxy resin, based on a total weight of the dual cure semi-structural adhesive composition being 100 wt%.

15. The dual-cure semi-structural adhesive composition of claim 1 , wherein the polyol is a compound containing two or more hydroxyl groups.

16. The dual cure semi-structural adhesive composition of claim 1 , wherein the polyol is a polyether polyol.

17. The dual-cure semi-structural adhesive composition of claim 1 , wherein the polyol is a polyether diol or polyether triol.

18. The dual cure semi-structural adhesive composition according to claim 1, wherein the polyol has a weight average molecular weight in the range of 500 to 3000 g / mol.

19. The dual cure semi-structural adhesive composition according to claim 1, wherein the dual cure semi-structural adhesive composition comprises 3 to 12 wt% of the polyol, based on a total weight of the dual cure semi-structural adhesive composition being 100 wt%.

20. 2. The dual-cure semi-structural adhesive composition of claim 1, wherein the cationic photoinitiator is one or more selected from diazonium salts, iodonium salts, sulfonium salts, antimonates, and iron arenes.

21. 2. The dual cure semi-structural adhesive composition of claim 1, wherein the dual cure semi-structural adhesive composition comprises 0.02 to 3 wt% of the cationic photoinitiator, based on a total weight of the dual cure semi-structural adhesive composition being 100 wt%.

22. A method for preparing a dual cure semi-structural adhesive composition, comprising uniformly mixing the components of the dual cure semi-structural adhesive composition of any one of claims 1 to 21.

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