A high impact-resistant glass film

Abstract

This invention belongs to the technical field of laminated glass encapsulation materials and discloses a high-impact-resistant glass adhesive film. The film is a five-layer co-extruded composite structure, sequentially comprising a first ethylene-vinyl acetate copolymer (EVA) resin layer, a first polar transition layer, a polyvinyl alcohol acetal resin layer, a second polar transition layer, and a second ethylene-vinyl acetate copolymer resin layer. Its core lies in the selection of materials to ensure that the surface free energy of the first and second polar transition layers is between the two EVA resin layers and the middle polyvinyl alcohol acetal resin layer, forming a precise surface free energy gradient. This design effectively releases interlayer stress, fundamentally solving long-term reliability problems such as easy debonding, delamination, and plasticizer migration at the interface when composite materials of different polarities are combined. Simultaneously, this structure possesses excellent wide-temperature-range impact resistance, high glass adhesion, low water vapor transmittance, and good optical performance, meeting the application requirements of high-end laminated glass in fields such as construction, automotive, and rail transportation.

Description

Technical Field

[0001] This invention belongs to the technical field of laminated glass encapsulation materials, specifically relating to a high-impact-resistant glass film. Technical Background

[0002] Laminated glass, as an important safety material, is widely used in civil buildings, the automotive industry, rail transportation, and high-end security fields due to its excellent penetration resistance and safety performance, as it does not easily shatter into flying fragments. The core performance of laminated glass is mainly determined by the encapsulating film of its internal interlayer. Currently, the mainstream encapsulating film materials in the industry are mainly divided into two categories: polyvinyl butyral (PVB) film and ethylene-vinyl acetate copolymer (EVA) film.

[0003] However, each type of adhesive film has its own performance limitations. While PVB films offer good impact resistance, they commonly suffer from plasticizer migration, leading to yellowing, hardening, and significant long-term performance degradation. Furthermore, their performance stability under high and low temperature conditions is insufficient. On the other hand, although EVA films exhibit good adhesion to glass substrates and are easy to process, their inherent impact resistance is poor. Under extreme temperature or stress conditions, they are prone to creep and delamination, making them unsuitable for high-safety-level applications.

[0004] To combine the excellent mechanical properties of PVB with the good adhesion of EVA, the industry has begun to explore the development of composite encapsulating films. For example, existing technologies disclose bilayer encapsulating films using a polyolefin layer combined with an EVA / PVB layer. While this design optimizes some performance aspects, it still has significant drawbacks: First, the direct composite of materials with different polarities (such as weakly polar polyolefin and strongly polar PVB) results in insufficient interfacial bonding. Under long-term humid and hot aging or thermal cycling conditions, the interlayer is prone to debonding and separation due to accumulated internal stress, severely impacting product lifespan and reliability. Second, the simple bilayer composite structure offers limited improvement in overall impact resistance and still cannot fully meet the extreme mechanical performance requirements of high-end applications such as rail transportation and aerospace. Furthermore, existing composite structures lack effective interlayer transition designs, failing to alleviate internal stress caused by differences in the thermal expansion coefficients of the materials, leading to interfacial problems such as bubbling and cracking during long-term use.

[0005] Therefore, there is an urgent need in this field to develop a new type of composite structure encapsulating film, which aims to fundamentally solve the problem of interfacial bonding stability between layers of materials with different polarities, while taking into account high impact resistance, wide temperature range adaptability and excellent long-term aging resistance, so as to fill the gap in existing technologies and meet the growing demand for high-end laminated glass applications. Summary of the Invention

[0006] To address the technical problems of existing single-material or simple composite glass adhesive films, such as poor interlayer bonding stability, insufficient impact resistance, weak wide temperature range adaptability, and susceptibility to delamination, peeling, or performance degradation after long-term use, the present invention aims to provide a high-impact glass adhesive film. This film, through a specific multi-layer composite structure design, introduces a polarity transition layer, aiming to fundamentally solve the interlayer bonding problem between materials of different polarities, thereby simultaneously achieving excellent glass bonding performance, high impact resistance, outstanding aging resistance, and a wide temperature range of applicability.

[0007] To achieve the above objectives, the present invention proposes a high-impact glass film, characterized in that it is a five-layer co-extruded composite structure, comprising, in sequence, a first ethylene-vinyl acetate copolymer resin layer, a first polar transition layer, a polyvinyl acetal resin layer, a second polar transition layer, and a second ethylene-vinyl acetate copolymer resin layer.

[0008] The polarity of the first polar transition layer and the second polar transition layer is greater than that of the adjacent first ethylene-vinyl acetate copolymer resin layer and the second ethylene-vinyl acetate copolymer resin layer, respectively, and is less than that of the polyvinyl acetal resin layer.

[0009] Furthermore, the matrix resin of the first polar transition layer and the second polar transition layer is selected from at least one of the following: ethylene-vinyl acetate copolymer with a vinyl acetate content of 33-45 wt%, ethylene-butyl acrylate copolymer with a butyl acrylate content of 33-45 wt%, graft-modified ethylene-vinyl acetate copolymer, and aliphatic thermoplastic polyurethane.

[0010] Furthermore, the surface free energy of the matrix resin of the first polar transition layer and the second polar transition layer is 30~45 mN / m.

[0011] Furthermore, the vinyl acetate content of the matrix resin of the first ethylene-vinyl acetate copolymer resin layer and the second ethylene-vinyl acetate copolymer resin layer is 15~32wt%.

[0012] Furthermore, the first ethylene-vinyl acetate copolymer resin layer and the second ethylene-vinyl acetate copolymer resin layer, based on 100 parts by weight of the matrix resin, contain 0.3 to 2.0 parts by weight of crosslinking agent, 0.1 to 1.5 parts by weight of crosslinking aid, and 0.1 to 1.0 parts by weight of silane coupling agent.

[0013] Furthermore, the grafted modified ethylene-vinyl acetate copolymer is selected from at least one of glycidyl methacrylate grafted ethylene-vinyl acetate copolymer and maleic anhydride grafted ethylene-vinyl acetate copolymer, with a grafting rate of 0.5~5.0 wt%.

[0014] Furthermore, the matrix resin of the polyvinyl acetal resin layer is selected from at least one of polyvinyl butyral, polyvinyl 2-ethylhexanal, polyvinyl n-octanal, polyvinyl n-hexanal, polyvinyl isooctanal, polyvinyl n-nonanal, polyvinyl n-decanal, and coacetals of polyvinyl butyral and C6-C10 long-chain aliphatic aldehydes.

[0015] Furthermore, the matrix resin of the high-impact glass film polyvinyl acetal resin layer is a co-acetal of polyvinyl butyral and C6-C10 long carbon chain aliphatic aldehydes, wherein the acetal structural unit corresponding to the long carbon chain aldehyde accounts for 20~50wt% of the total acetal units.

[0016] Furthermore, the total thickness of the high-impact glass film is 300~800μm, wherein the single-layer thickness of the first polar transition layer and the second polar transition layer is 10~80μm, and the thickness of the polyvinyl acetal resin layer is 100~400μm.

[0017] Furthermore, the high-impact glass film has a light transmittance of ≥88%, a haze of ≤3.0%, and a yellowing index ΔYI of ≤2.0.

[0018] Furthermore, the water vapor transmission rate of the high-impact glass film is ≤2.5g / m²·day.

[0019] The high-impact glass film according to claim 1, wherein the first polar transition layer and the second polar transition layer of the second ethylene-vinyl acetate copolymer resin layer further contain ultraviolet absorbers and / or hindered amine light stabilizers.

[0020] Compared with the prior art, the present invention has the following significant advantages:

[0021] First, by introducing a polar transition layer with polarity between the EVA resin layer and the acetal layer, a polarity gradient is constructed, which effectively alleviates the interfacial stress generated when materials with different polarities are directly composited, and significantly improves the interlayer adhesion and overall mechanical properties under normal conditions.

[0022] By designing a surface free energy gradient for each material layer, the problem of long-term interfacial stability was solved. The surface free energy of the polar transition layer lies between the EVA layer and the acetal layer, effectively alleviating the interfacial stress caused by the direct composite of materials with different polarities due to differences in thermal expansion coefficients. This improves interlayer compatibility, strengthens adhesion, and provides a physical basis for the excellent long-term aging resistance of the film.

[0023] The film provided by this invention has a light transmittance of ≥88%, a haze of ≤3.0%, and a yellowing index ΔYI of ≤2.0 after 1000 hours of QUV accelerated aging, ensuring the high optical quality and long-term weather resistance of the product. It can effectively inhibit interface failure caused by moisture intrusion and improve the reliability of laminated glass in humid environments.

[0024] The adhesive film of this invention not only meets stringent quantitative indicators such as optical performance, weather resistance, and barrier properties, but also satisfies the high standards of safety, durability, and optical reliability required in fields such as building curtain walls, automotive glass, and rail transportation. Attached Figure Description

[0025] Figure 1 This is a schematic cross-sectional view of the layered structure of a preferred embodiment of the high impact-resistant glass film of the present invention.

[0026] In the figure: 100 - High impact resistant glass film; 11 - First ethylene-vinyl acetate copolymer resin layer; 21 - First polar transition layer; 31 - Polyvinyl alcohol acetal resin layer; 22 - Second polar transition layer; 12 - Second ethylene-vinyl acetate copolymer resin layer. Detailed Implementation

[0027] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. It should be understood that the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] In this invention, "polarity" refers to the inherent property of polymer materials due to the presence of asymmetric polar functional groups (such as ester groups, carboxyl groups, hydroxyl groups, acid anhydride groups, ionic groups, etc.) in the molecular chain, which is mainly manifested as affinity for polar substances.

[0029] In some embodiments, the first ethylene-vinyl acetate copolymer resin layer and the second ethylene-vinyl acetate copolymer resin layer serve as surface adhesive layers of the adhesive film, with the matrix resin being ethylene-vinyl acetate copolymer (EVA). The content of vinyl acetate (VA) monomer is typically between 15 wt% and 32 wt% to ensure good glass adhesion, mechanical strength, and processability. In practical applications, the specific selection of the VA content can be optimized based on the required bond strength, flexibility, and processing fluidity: a moderate VA content can provide better mechanical strength and dimensional stability while maintaining good adhesion, enabling the material to form a high-strength and long-term stable bond with the glass substrate.

[0030] In some embodiments, the matrix resins of the first polar transition layer and the second polar transition layer are selected from one or more of the following materials for compounding: ethylene-vinyl acetate copolymer with a vinyl acetate content of 33-45 wt%, ethylene-butyl acrylate copolymer with a butyl acrylate content of 33-45 wt%, graft-modified ethylene-vinyl acetate copolymer, and at least one of aliphatic thermoplastic polyurethane.

[0031] In EVA copolymers, VA repeating units are the main source of polarity. The density of polar ester groups in EVA resin molecular chains with VA content greater than or equal to 33 wt% increases significantly, and it has excellent compatibility with EVA resin used as the surface layer; at the same time, it has good affinity with the core layer acetal resin, making it an economical and practical choice for achieving polarity transition.

[0032] For the same reason, in another embodiment, an ethylene-butyl acrylate copolymer with a butyl acrylate content of 33-45 wt% is selected as the matrix resin for the first polar transition layer and the second polar transition layer. The longer butyl side chains in the EBA molecular chain may bring better flexibility.

[0033] In other embodiments, the grafted modified ethylene-vinyl acetate copolymer, due to the introduction of reactive epoxy groups or anhydride groups on its molecular chain, can chemically react with adjacent layers during processing or use to form covalent bonds, thereby providing the strongest interfacial bonding and long-term stability.

[0034] For example, to enhance the interfacial durability of one side of the film under extreme humid and hot conditions, GMA-g-EVA or HMA-g-EVA can be used in the polar layer on that side.

[0035] The polarity of ordinary EVA mainly comes from the ester groups in the side chain, while the polarity of aliphatic thermoplastic polyurethane comes from the strong polar hydrogen-bonded groups on the main chain. Its polar strength and ability to form hydrogen bonds are usually much higher than those of the ester groups in ordinary EVA, so it can be used as a matrix resin for a strong polar transition layer.

[0036] In other embodiments, two or more of the above-mentioned resins can be blended to precisely control the polarity, flowability, and compatibility with the materials on both sides of the transition layer, thereby further optimizing the interface performance.

[0037] In some embodiments, the polyvinyl acetal resin layer serves as the mechanical support core layer of the film, and its matrix resin may be selected from at least one of the following materials: polyvinyl butyral (PVB), polyvinyl butyral-2-ethylhexanal coacetal, polyvinyl 2-ethylhexanal, polyvinyl n-octanal, polyvinyl n-hexanal, polyvinyl butyral-n-hexanal coacetal, polyvinyl isooctanal, polyvinyl n-nonanal, and polyvinyl n-decanal.

[0038] Ordinary PVB resin is suitable for general applications such as construction and automobiles, and has advantages in cost and supply chain; while long-chain modified polyvinyl acetal (such as n-decanal) can provide better wide temperature range performance and lower high-temperature creep, making it more suitable for high-end applications such as rail transit and extreme environments.

[0039] In some embodiments, the film preparation process is as follows: a five-layer co-extrusion casting process is used for integral molding. The raw materials corresponding to each layer are melted and plasticized separately, and then extruded through a five-layer co-extrusion die. The die temperature is controlled at 145°C, the casting speed is controlled at 3 m / min, and the film is cooled and shaped on a cooling roller at 30°C to obtain a composite film with clear interlayer interfaces, uniform thickness, and no defects.

[0040] The raw materials used in this embodiment are all common commercially available products.

[0041] Test method:

[0042] Surface Free Energy: Surface free energy and its components: The static contact angles of deionized water and diiodomethane as probe liquids on the sample surface were measured using a contact angle meter (KRUSS DSA, Germany). At least five measurements were taken at different locations for each sample, and the average value was calculated. The total surface free energy of the sample was calculated based on the Owens-Wendt-Rabel-Kaelble (OWRK) model.

[0043] Yellowing index (ΔYI): Tested according to GB / T 29848, after 1000 hours of QUV accelerated aging, the yellowing index ΔYI of the film should be ≤ 2.0.

[0044] Water vapor transmission rate [g / (m²·day)]: Tested according to ASTM F1249 at 40℃ / 90%RH. The required water vapor transmission rate of the membrane is ≤2.5 g / (m²·day).

[0045] Glass bonding strength (N / cm): Tested according to the bonding strength test method specified in GB 15763.3-2009 "Safety Glass for Building - Part 3: Laminated Glass".

[0046] -40℃ Drop Ball Impact Test Results: GB / T 9962-1999 Drop Ball Impact Test Method.

[0047] Interface condition after 2000 hours of damp heat aging: GB / T 5137.3 includes a moisture resistance test, and 2000 hours is a relatively long test time.

[0048] Interface condition after 1000 cycles of hot and cold cycling: Temperature change test method in GB / T 2423 series standards.

[0049] Light transmittance (%): Tested in accordance with GB / T 2680-2021 "Determination of visible light transmittance, direct solar transmittance, total solar transmittance, ultraviolet transmittance and related window glass parameters of architectural glass".

[0050] Haze (%): Tested in accordance with GB / T 2410-2008 "Determination of light transmittance and haze of transparent plastics".

[0051] Example 1

[0052] The high-impact resistant glass film provided in this embodiment is as follows: Figure 1 As shown, this is a five-layer composite structure, comprising, in sequence, a first ethylene-vinyl acetate copolymer resin layer 11, a first polar transition layer 21, a polyvinyl alcohol acetal resin layer 31, a second polar transition layer 22, and a second ethylene-vinyl acetate copolymer resin layer 12. The first polar transition layer 21 and the second polar transition layer 22 have equal polarity, and their polarities are greater than those of the first ethylene-vinyl acetate copolymer resin layer 11 and the second ethylene-vinyl acetate copolymer resin layer 12, respectively, but less than the polarity of the polyvinyl alcohol acetal resin layer 31.

[0053] The first ethylene-vinyl acetate copolymer resin layer 11 and the second ethylene-vinyl acetate copolymer resin layer 12 are made of the same material, with the matrix resin being an ethylene-vinyl acetate copolymer containing 28 wt% VA. The raw material composition, based on 100 parts by weight of this EVA resin, includes: 100 parts of EVA resin with 28 wt% VA content, 1.0 part of TBEC crosslinking agent, 1.0 part of dipentaerythritol hexaacrylate, 1.0 part of KH-171 silane coupling agent, 1.0 part of antioxidant, and 1.0 part of UV-329 ultraviolet absorber. Its surface free energy is measured to be 28 mN / m.

[0054] The first polar transition layer 21 and the second polar transition layer 22 are made of the same material: the matrix resin is an ethylene-vinyl acetate copolymer with a VA content of 40 wt%. The raw material composition, based on 100 parts by weight of this high-VA-content EVA resin, includes: 100 parts of the resin, 0.3 parts of antioxidant, and 0.3 parts of UV-329. Its surface free energy is measured to be 30 mN / m.

[0055] Polyvinyl acetal resin layer 31: The matrix resin is ordinary automotive-grade polyvinyl butyral (PVB). The raw material composition, based on 100 parts by weight of PVB resin, includes: 100 parts PVB, 25 parts 3GO plasticizer, 1.5 parts antioxidant, and 0.3 parts UV-329.

[0056] Thickness: The total thickness of the film is 0.76 mm. The polyvinyl acetal resin layer 31 is 0.36 mm thick, the first polar transition layer 21 and the second polar transition layer 22 are both 0.10 mm thick, and the first ethylene-vinyl acetate copolymer resin layer 11 and the second ethylene-vinyl acetate copolymer resin layer 12 are both 0.10 mm thick.

[0057] Example 2

[0058] The difference between this embodiment and Embodiment 1 lies in the matrix resin of the polyvinyl acetal resin layer 31.

[0059] Polyvinyl acetal resin layer 31: The matrix resin is polyvinyl butyral-2-ethylhexanal co-acetal (modified PVB-A), wherein the acetal structure corresponding to 2-ethylhexanal accounts for 30 wt%. The raw material composition, based on 100 parts by weight of this resin, includes: 100 parts of modified PVB-A, 10 parts of polyester plasticizer, 1.5 parts of antioxidant, and 0.3 parts of UV-329.

[0060] Example 3

[0061] The difference between this embodiment and Embodiment 1 lies in the matrix resin of the first polar transition layer and the second polar transition layer.

[0062] The first polar transition layer 21 and the second polar transition layer 22 are made of the same material: the raw material composition, based on 100 parts by weight of polyurethane (TPU), includes: 100 parts of optical-grade polyester TPU resin, 0.3 parts of antioxidant, and 0.3 parts of UV-329. Its surface free energy is measured to be 45 mN / m.

[0063] Example 4

[0064] The difference between this embodiment and Embodiment 1 lies in the matrix resin of the first polar transition layer and the second polar transition layer.

[0065] The first polar transition layer 21 and the second polar transition layer 22 are made of the same material: the matrix resin is an ethylene-butyl acrylate copolymer (EBA, grade reference Arkema 35BA40) with a butyl acrylate (BA) content of 38 wt%. The raw material composition, based on 100 parts by weight of this EBA resin, includes: 100 parts of the EBA resin, 0.3 parts of antioxidant, and 0.3 parts of UV-329 ultraviolet absorber. Its surface free energy is measured to be 35 mN / m.

[0066] Comparative Example

[0067] Comparative Example 1:

[0068] The test was conducted on a commercially available ordinary single-layer PVB film with a thickness of 0.76 mm.

[0069] Comparative Example 2:

[0070] The glass sealant film has a three-layer composite structure, consisting of a first ethylene-vinyl acetate copolymer resin layer, a polyvinyl alcohol acetal resin layer, and a second ethylene-vinyl acetate copolymer resin layer stacked sequentially, without a polar transition layer. The thickness of each layer and the formulation of the EVA and polyvinyl alcohol acetal resin layers are the same as those of the corresponding layers in Example 1.

[0071] Performance Testing and Results Analysis

[0072]

[0073] In summary, all embodiments achieved a surface free energy gradient through material selection, and their performance was significantly better than that of the comparative examples without gradient design, proving that this design is the core solution to long-term interface problems.

Claims

1. A high-impact glass sealant film, characterized in that, It is a five-layer co-extruded composite structure, which includes, in sequence, a first ethylene-vinyl acetate copolymer resin layer, a first polar transition layer, a polyvinyl acetal resin layer, a second polar transition layer, and a second ethylene-vinyl acetate copolymer resin layer. The polarity of the first polar transition layer and the second polar transition layer is greater than that of the adjacent first ethylene-vinyl acetate copolymer resin layer and the second ethylene-vinyl acetate copolymer resin layer, respectively, and is less than that of the polyvinyl acetal resin layer. The matrix resin of the first polar transition layer and the second polar transition layer is selected from at least one of the following: ethylene-vinyl acetate copolymer with a vinyl acetate content of 33-45 wt%, ethylene-butyl acrylate copolymer with a butyl acrylate content of 33-45 wt%, graft-modified ethylene-vinyl acetate copolymer, and aliphatic thermoplastic polyurethane.

2. The high impact-resistant glass film according to claim 1, characterized in that, The surface free energy of the matrix resin of the first polar transition layer and the second polar transition layer is 30~45 mN / m, and the polar force component is 5~20 mN / m.

3. The high impact-resistant glass film according to claim 1 or 2, characterized in that, The vinyl acetate content of the matrix resin of the first ethylene-vinyl acetate copolymer resin layer and the second ethylene-vinyl acetate copolymer resin layer is 15~32wt%.

4. The high impact-resistant glass film according to claim 3, characterized in that, The first ethylene-vinyl acetate copolymer resin layer and the second ethylene-vinyl acetate copolymer resin layer contain, based on 100 parts by weight of the matrix resin, 0.3 to 2.0 parts by weight of crosslinking agent, 0.1 to 1.5 parts by weight of crosslinking aid, and 0.1 to 1.0 parts by weight of silane coupling agent.

5. The high impact-resistant glass film according to claim 1, characterized in that, The grafted modified ethylene-vinyl acetate copolymer is selected from at least one of glycidyl methacrylate grafted ethylene-vinyl acetate copolymer and maleic anhydride grafted ethylene-vinyl acetate copolymer, with a grafting rate of 0.5~5.0 wt%.

6. The high impact-resistant glass film according to claim 1, characterized in that, The matrix resin of the polyvinyl acetal resin layer is selected from at least one of polyvinyl butyral, polyvinyl 2-ethylhexanal, polyvinyl n-octanal, polyvinyl n-hexanal, polyvinyl isooctanal, polyvinyl n-nonanal, polyvinyl n-decanal, and coacetals of polyvinyl butyral and C6-C10 long-chain aliphatic aldehydes.

7. The high impact-resistant glass film according to claim 6, characterized in that, The matrix resin of the polyvinyl acetal resin layer is a co-acetal of polyvinyl butyral and C6-C10 long carbon chain aliphatic aldehydes, wherein the acetal structural unit corresponding to the long carbon chain aldehyde accounts for 20~50wt% of the total acetal units.

8. The high impact-resistant glass film according to claim 1, characterized in that, The total thickness of the five-layer co-extruded composite structure is 300~800μm, wherein the single-layer thickness of the first polar transition layer and the second polar transition layer is 10~80μm, and the thickness of the polyvinyl acetal resin layer is 100~400μm.

9. The high impact-resistant glass film according to claim 1, characterized in that, Light transmittance ≥88%, haze ≤3.0%, yellowing index ΔYI ≤2.

0.

10. The high impact-resistant glass film according to claim 1 or 9, characterized in that, Water vapor permeability ≤2.5g / m²·day.

11. The high impact-resistant glass film according to claim 1, characterized in that, The first polar transition layer and the second polar transition layer also contain ultraviolet absorbers and / or hindered amine light stabilizers.

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