UV-curable semi-structure adhesive film

Abstract

The invention relates to a UV-curable semi-structured adhesive film, which comprises the following components in percentage by weight: 35-55% of an acrylic acid alkene derivative polymer, the glass transition temperature Tg of which is between-40 DEG C and-10 DEG C, and the adhesive film also comprises a UV-curable semi-structured adhesive film. Raw materials of the acrylic acid alkene derivative polymer comprise the following components: a C4-C18 acrylate monomer, a hydrophilic monomer, an epoxy group-containing acrylate monomer and a crosslinking monomer; 0.5 to 2% of a cationic initiator; 30-60% of bisphenol A epoxy resin, wherein the bisphenol A epoxy resin comprises liquid epoxy resin and solid epoxy resin; 1 to 5% of polyether polyol; 1 to 10% of an alicyclic epoxy resin; 5 to 15 percent of epoxy modified organic silicon resin; 0.5 to 2% of a silane coupling agent; and 0.05 to 0.15% of a titanate coupling agent. The adhesive film disclosed by the invention is good in aging resistance, is not easy to overflow in a storage process, and can meet the production and transportation requirements of products.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and more particularly to a UV-curable semi-structural adhesive film. Background Technology

[0002] In recent years, the development of new energy vehicles has been rapid. Power batteries are the core component of new energy vehicles, and the battery cells are bonded to the battery casing using adhesives. UV-cured PUR adhesives have advantages such as good wettability, high bonding strength, and good insulation, making them the mainstream solution for cell bonding. However, they are usually two-component, requiring on-site mixing and have a short shelf life. Using them as adhesives presents significant processing difficulties and makes rework challenging. While tapes can address these issues, they often cannot simultaneously guarantee good wettability, sealing properties, and adhesive overflow characteristics. Furthermore, their aging resistance remains a major challenge.

[0003] In existing technologies, acrylates and epoxy resins are generally used as the main components, with the addition of cationic initiators to achieve UV delayed curing. However, these materials are usually unable to withstand aging at 85℃ / 85%RH for 1000 hours. Some technologies introduce hydroxyl polyurethanes to improve the wettability of the substrate, but this leads to a decrease in initial shear strength and a tendency for adhesive overflow. More commonly, these materials are used in the form of adhesives. For example, some technologies incorporate carboxyl-terminated polyester-modified aliphatic epoxy resins to provide better weather resistance to the epoxy cured product, but the curing speed is relatively fast, making rework difficult. Others use isocyanate-terminated polyurethanes as the main component to create two-component UV-curing adhesives with excellent aging performance, but a short pot life and a tendency to deteriorate.

[0004] For example, Chinese patent CN117136223A discloses a UV-curable adhesive composition, the organic component of which includes a (meth)acrylate component; epoxy resin; core-shell rubber particles; an effective amount of cationic photoinitiator; and up to 10% by weight of amphoteric inorganic filler. The added amphoteric inorganic filler aluminum hydroxide improves the interfacial peel strength; the added polybutadiene core-shell rubber improves toughness and impact resistance, but its anti-aging properties are poor, and its shear strength after 1 hour of curing is poor, which cannot meet the handling requirements in the production process.

[0005] CN 116285788 A discloses a delayed-curing pressure-sensitive adhesive, pressure-sensitive tape and its preparation method, using a polymer film-forming matrix and epoxy resin as the main raw materials, and adding cationic photoinitiators, curing agents, diluent monomers and additives. By adding hydroxyl polyurethane to acrylate, the wettability is improved; however, its open operation time is too long, and it cannot quickly build up strength in a short period of time after UV exposure, which affects production flow and transportation.

[0006] CN 120310488 A discloses a UV delayed-curing adhesive and its preparation method. The UV delayed-curing adhesive is composed of specific proportions of alicyclic epoxy resin, modified alicyclic epoxy resin, polycaprolactone polyol, reactive diluent, photoinitiator, silane coupling agent, and fumed silica. The addition of carboxyl-terminated polyester-modified alicyclic epoxy resin provides better weather resistance to the cured epoxy, but the curing speed is relatively fast, making rework difficult.

[0007] CN115772379A discloses a UV-delayed curing two-component polyurethane adhesive comprising two independently stored components, A and B. This delayed-curing two-component polyurethane adhesive has excellent aging performance, but the two components are not conducive to use, have a short pot life, and are prone to deterioration.

[0008] Therefore, how to provide an adhesive film that combines wettability, sealing properties, adhesive overflow characteristics, and anti-aging properties is a research direction that those skilled in the art are dedicated to. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a UV-curable semi-structural adhesive film.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is: a UV-curable semi-structural adhesive film, wherein the adhesive film comprises the following raw materials by weight percentage: 1) 35-55% of acrylate derivative polymers, with a glass transition temperature (Tg) between -40°C and -10°C, wherein the raw materials of the acrylate derivative polymers contain the following components: C4-C18 acrylate monomers, hydrophilic monomers, epoxy-containing acrylate monomers, and crosslinking monomers. 2) 0.5-2% cationic initiator; 3) 30-60% bisphenol A epoxy resin, wherein the bisphenol A epoxy resin comprises liquid epoxy resin and solid epoxy resin; 4) 1-5% polyether polyol; 5) 1-10% alicyclic epoxy resin; 6) 5-15% epoxy-modified silicone resin; 7) 0.5-2% silane coupling agent; 8) 0.05-0.15% titanate coupling agent.

[0011] As one specific implementation, the adhesive film satisfies the following conditions: 1) No glue will overflow after being left at room temperature for 12 months; 2) It will not warp or slip after being adhered to the substrate before UV curing; 3) The overlap shear strength after 1 hour of UV curing is >0.5MPa, and the overlap shear strength after 24 hours of UV curing is >8MPa; 4) After 1000 hours of aging at 85℃ / 85%RH, the strength decreases by less than 20%; 5) After boiling in high pressure at 130℃ for 48 hours, the strength decreases by less than 40%.

[0012] In one specific embodiment, the weight-average molecular weight of the polyether polyol is between 400 and 2000 g / mol, and the polyether polyol is a diol or a triol.

[0013] In one specific implementation, the cationic initiator is selected from onium salts and / or iodonium salt initiators.

[0014] In one specific implementation, the mass ratio of liquid epoxy resin to solid epoxy resin in bisphenol A epoxy resin is between 2.5:1 and 3.5:1.

[0015] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: 1) The present invention provides a UV-curable semi-structured adhesive film, in which epoxy-modified silicone resin is added to an adhesive system mainly composed of acrylate derivative polymer and bisphenol A epoxy resin to improve the aging resistance of the adhesive. 2) By reasonably adjusting the proportion of film-forming substances in the raw materials, using a combination of low-Tg acrylic derivatives and solid epoxy resins, and then crosslinking with titanate coupling agents, a film that is not prone to overflow when stored at room temperature can be obtained. 3) Furthermore, by controlling the ratio of alicyclic epoxy resin, polyether polyol and cationic initiator, the shear strength after UV treatment is >0.5MPa after 1 hour to meet the needs of product production and transportation, and the final strength is >8MPa after 24 hours. Detailed Implementation

[0016] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0017] The following provides a UV-curable semi-structural adhesive film, which comprises the following raw materials by weight percentage: 1) 35-55% of acrylate derivative polymers, with a glass transition temperature (Tg) between -40°C and 10°C, wherein the raw materials of the acrylate derivative polymers contain the following components: C4-C18 acrylate monomers, hydrophilic monomers, epoxy-containing acrylate monomers, and crosslinking monomers. 2) 0.5-2% cationic initiator; 3) 30-60% bisphenol A epoxy resin, wherein the bisphenol A epoxy resin comprises liquid epoxy resin and solid epoxy resin; 4) 1-5% of polyether polyol, wherein the weight-average molecular weight of the polyether polyol is between 400-2000 g / mol, and the polyether polyol is a diol or a triol. 5) 1-10% alicyclic epoxy resin; 6) 5-15% epoxy-modified silicone resin; 7) 0.5-2% silane coupling agent; 8) 0.05-0.15% titanate coupling agent.

[0018] I. The following provides the preparation of acrylate derivative polymers. 1) Acrylic polymer S1 In a reaction vessel equipped with a thermometer, a stirrer, and a nitrogen injection tube, 60.5 g of butyl acrylate, 33.0 g of methyl acrylate, 0.5 g of glycidyl methacrylate, 6.0 g of acrylic acid, and 60 g of ethyl acetate were added. The mixture was continuously stirred at 100 rpm / min while the temperature was raised to 61°C, and nitrogen was purged at a flow rate of 100 mL / min for 20 min. Then, 0.54 g of azobisisobutyronitrile was added and the reaction proceeded for 2 h, followed by another 0.54 g of azobisisobutyronitrile and a reaction proceeding for 3 h. Finally, the temperature was raised to 75°C, and another 0.54 g of azobisisobutyronitrile was added and the reaction proceeded for 3 h. The mixture was then poured off and retained to obtain an acrylate polymer with a solid content of 40%.

[0019] 2) Acrylic polymer S2 The ingredients of acrylate polymer S2 are 44.5g butyl acrylate, 49.0g methyl acrylate, 0.5g glycidyl methacrylate, and 6.0g acrylic acid. The preparation process is the same as that of acrylate polymer S1.

[0020] 3) Acrylic polymer S3 The ingredients of acrylate polymer S3 are 30g butyl acrylate, 63.5g methyl acrylate, 0.5g glycidyl methacrylate, and 6.0g acrylic acid. The preparation process is the same as that of acrylate polymer S1.

[0021] 4) Acrylic polymer S4 The ingredients of acrylate polymer S4 are 50.0g butyl acrylate, 35.0g methyl acrylate, and 15.0g glycidyl methacrylate. The preparation process is the same as that of acrylate polymer S1.

[0022] 5) Acrylic polymer S5 The ingredients of acrylate polymer S5 are 29.5g butyl acrylate, 64.0g methyl acrylate, 0.5g glycidyl methacrylate, and 6.0g acrylic acid. The preparation process is the same as that of acrylate polymer S1.

[0023] 6) Acrylic polymer S6 The ingredients of acrylate polymer S6 are 76g butyl acrylate, 17.5g methyl acrylate, 0.5g glycidyl methacrylate, and 6.0g acrylic acid. The preparation process is the same as that of acrylate polymer S1.

[0024] The ingredients for S1 to S4 are shown in Table 1, and the content of each substance is in g.

[0025] Table 1

[0026] II. The following describes the preparation of a UV-curable semi-structural adhesive film. The preparation process is as follows: Acrylic polymers, cationic initiators, polyether polyols, liquid epoxy resins, solid epoxy resins, alicyclic epoxy resins, epoxy-modified silicone resins, titanate coupling agents, silane coupling agents, and ethyl acetate of varying masses are taken; after stirring and dissolving evenly, the mixture is degassed under a vacuum of 0.95 MPa for 2 hours to obtain an adhesive resin composition for adhesive sheets. The specific material grades and manufacturers used are shown in Table 2, and the main ingredients of the adhesive are shown in Table 3.

[0027] Table 2

[0028] Table 3

[0029] III. Preparation process of adhesive film The mixed adhesive resin compositions E1-E10 and CE1-CE11 were poured onto a polyethylene terephthalate (PET) release film (with the release surface in contact with the adhesive resin composition), and then coated into a 100 μm film using a coater. After standing at room temperature for 3 minutes, the film was placed in an oven at 50°C for 5 minutes and then transferred to an oven at 85°C for 20 minutes to obtain adhesive films E1-E10 and CE1-CE11.

[0030] The transparent adhesive sheets E1-E10 and CE1-CE11 obtained above were tested using the following methods: (a) Determination of overlapping shear strength According to SAE J1523_202101 standard testing, the adhesive film was cut into 20mm*15mm rectangles, the light release film was peeled off, and it was attached to a 1.5mm thick 25mm*100mm 3003 aluminum plate; then the heavy release film was peeled off, and 100mw / cm was used. 2 The film was irradiated with 365nm UV light for 30 seconds, and then immediately overlapped with an aluminum plate of the same size. A force of 2kg was then applied continuously for 2 minutes. After the film had cured, it was tested using a Shimadzu AGS-X tensile testing machine at a speed of 1.27mm / min.

[0031] (II) Determination of 1 kap creep at 25℃ An adhesive sheet with a thickness of 0.05 mm, a width of 10 mm, and a length of 10 mm was prepared and stacked to a thickness of 1 mm. A circular sample with a diameter of 8 mm and a thickness of 1 mm was obtained using a special punch. The dynamic viscoelasticity was measured using a wide-range dynamic viscoelasticity measuring device (TA Instruments, Discovery HR-10) in Creep mode at a temperature of 25°C, a pressure of 1 kPa, and a time of 300 s. The deformation strain corresponding to 300 s was used as the test result. When the strain was greater than 150%, it was determined that there was a risk of adhesive overflow.

[0032] (III) Accelerated aging test at 85℃ / 85%RH The prepared overlapping shear strength test specimens were placed in a constant temperature and humidity chamber at 85℃ / 85%RH for 1000 hours, then removed and left to stand at room temperature for 1 day before the overlapping shear strength test was performed.

[0033] (iv) 130℃ PCT accelerated aging test The prepared overlapping shear strength test specimens were placed in a PCT aging chamber at 130℃ for 48 hours, then removed and left to stand at room temperature for 1 day before the overlapping shear strength test was performed.

[0034] The test results are shown in Table 4.

[0035] Table 4

[0036] As shown in Table 4, under the same conditions of other components, using acrylate polymers with a Tg between -40℃ and -10℃ and containing C4-C18 acrylate monomers, hydrophilic monomers, epoxy-containing acrylate monomers, and crosslinking monomers in the raw materials, the properties of the tapes prepared can all meet the requirements of overlapping shear strength > 0.5MPa after 1 hour of UV curing and overlapping shear strength > 8MPa after 24 hours of UV curing, such as E1, E7, E8, E9, and E10. However, because the raw material of S4 does not contain acrylic acid, its overlapping shear strength after 1 hour of UV curing is less than 0.5MPa, which cannot meet the handling requirements in the production process, as shown in comparative example CE2.

[0037] Compared to E7, E2 lacks the titanate coupling agent HY-AA-75, resulting in adhesive overflow. Furthermore, its overlap shear strength after 24 hours of UV curing is less than 8 MPa. Similarly, compared to E1, E5 also lacks the titanate coupling agent, leading to adhesive overflow. Additionally, its strength decreases by more than 20% after 1000 hours of aging at 85℃ / 85%RH, and by more than 40% after 48 hours of high-pressure water boiling at 130℃.

[0038] Compared to E8, E3 has a titanate coupling agent content of less than 0.05%, resulting in an overlap shear strength of less than 8 MPa after 24 hours of UV curing. Compared to E1, CE5 has a titanate coupling agent content of less than 0.05%, leading to adhesive overflow. Therefore, the amount of titanate coupling agent added should not be less than 0.05%.

[0039] Compared to E1, E4 does not contain the alicyclic epoxy resin DE021, resulting in an overlap shear strength of less than 0.5 MPa after 1 hour of UV curing, which cannot meet the handling requirements during the production process.

[0040] Compared to E1, E6 contains 0.15% titanate coupling agent, and the tape made from it has superior performance in all aspects. This shows that, with the same content of other components, when the content of titanate coupling agent is controlled between 0.05% and 0.15%, the resulting tape has excellent performance in all aspects.

[0041] The difference between CE1 and E1 is that CE1 does not contain alicyclic epoxy resin DE021 and epoxy-modified silicone resin SEI8030, resulting in its overlap shear strength of less than 8 MPa after 24 hours of UV curing.

[0042] The difference between CE8 and E1 is that CE8 does not contain polyol S3007. As we can see from Table 4, after aging, the shear strength of the tape is less than 8 MPa.

[0043] CE3, based on CE8, increases the dosage of cationic initiator 6976, resulting in an overlap shear strength of less than 8 MPa after 24 hours of UV curing of the tape. This indicates that, with the same dosage of other components, the dosage of initiator should not exceed 2%.

[0044] The difference between CE4 and E1 is that CE4 contains 70% S1 and no solid epoxy resin 901, resulting in an overlap shear strength of less than 8 MPa after 24 hours of UV curing.

[0045] The difference between CE6, CE7, and E1 lies in the ratio of liquid epoxy resin to solid epoxy resin in the raw materials. In E1, the mass ratio of liquid epoxy resin to solid epoxy resin is 2.7:1, in CE6 it is 2:1, and in CE7 it is 3.2:1. Tapes made from E1 and CE7 exhibit excellent properties, while tapes made from CE6 have an overlap shear strength of less than 8 MPa after 24 hours of UV curing. Therefore, with other components remaining the same, the mass ratio of liquid epoxy resin to solid epoxy resin in bisphenol A epoxy resin should be controlled between 2.5:1 and 3.5:1.

[0046] The difference between CE9 and E1 is that CE9 does not contain epoxy-modified silicone resin SEI8030, resulting in an overlap shear strength of less than 8 MPa after 24 hours of UV curing.

[0047] The difference between CE10, CE11 and E1 lies in the dosage of acrylate polymer. Test data shows that when the dosage of acrylate polymer reaches 60%, glue overflow occurs; when the dosage of acrylate polymer is as low as 30%, the overlap shear strength after 1 hour of UV curing is less than 0.5 MPa, and the overlap shear strength after 24 hours of UV curing is less than 8 MPa. Therefore, the dosage of acrylate polymer is set between 35% and 55%.

[0048] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A UV-curable semi-structural adhesive film, characterized in that, The adhesive film comprises, by weight percentage, the following raw materials: 1) 35-55% of acrylate derivative polymers, with a glass transition temperature (Tg) between -40°C and -10°C, wherein the raw materials of the acrylate derivative polymers contain the following components: C4-C18 acrylate monomers, hydrophilic monomers, epoxy-containing acrylate monomers, and crosslinking monomers. 2) 0.5-2% cationic initiator; 3) 30-60% bisphenol A epoxy resin, wherein the bisphenol A epoxy resin comprises liquid epoxy resin and solid epoxy resin; 4) 1-5% polyether polyol; 5) 1-10% alicyclic epoxy resin; 6) 5-15% epoxy-modified silicone resin; 7) 0.5-2% silane coupling agent; 8) 0.05-0.15% titanate coupling agent.

2. The UV-curable semi-structural adhesive film according to claim 1, characterized in that, The adhesive film meets the following conditions: 1) No glue will overflow after being left at room temperature for 12 months; 2) It will not warp or slip after being adhered to the substrate before UV curing; 3) The overlap shear strength after 1 hour of UV curing is >0.5MPa, and the overlap shear strength after 24 hours of UV curing is >8MPa. 4) After 1000 hours of aging at 85℃ / 85%RH, the strength decreases by less than 20%; 5) After boiling in high pressure at 130℃ for 48 hours, the strength decreases by less than 40%.

3. The UV-curable semi-structural adhesive film according to claim 1, characterized in that, The weight-average molecular weight of the polyether polyol is between 400 and 2000 g / mol, and the polyether polyol is a diol or a triol.

4. The UV-curable semi-structural adhesive film according to claim 1, characterized in that, The cationic initiator is selected from onium salts and / or iodonium salt initiators.

5. The UV-curable semi-structural adhesive film according to claim 1, characterized in that, In bisphenol A epoxy resin, the mass ratio of liquid epoxy resin to solid epoxy resin is between 2.5:1 and 3.5:1.

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