Composite coated polycarbonate sheet and method of making same

Abstract

The present application relates to a kind of composite coating polycarbonate board and its preparation method, including polycarbonate board substrate, and interface flame-retardant layer and EB wear-resistant layer sequentially arranged on the surface of the polycarbonate board substrate.The composite coating structure of the polycarbonate board surface of the present application makes polycarbonate board can give consideration to flame-retardant property, surface hardness, wear resistance and interlayer adhesion, reduce interlayer cracking and delamination risk, with good market application prospect.

Description

Technical Field

[0001] This invention belongs to the field of functional coating technology for sheet surfaces, and specifically relates to a composite coated polycarbonate sheet and its preparation method. Background Technology

[0002] Polycarbonate sheets are widely used in electronic displays, home appliance exterior components, automotive interior and exterior trim, architectural lighting and protection, and other fields due to their high transparency, excellent impact resistance, good dimensional stability, and processing adaptability. Because polycarbonate materials are relatively soft, easily scratched, and have limited abrasion resistance, a hardened coating is usually applied to their surface in practical applications to improve surface hardness, abrasion resistance, weather resistance, and chemical resistance. In existing technologies, hard coating solutions for polycarbonate substrates mainly employ ultraviolet light curing, thermal curing, or other radiation curing methods to form a surface protective layer. Multi-layer structures combining adhesive layers and hard coating films are also used to improve surface properties and substrate compatibility.

[0003] In the prior art, there are various hardening coating solutions for polycarbonate sheets. For example, patent CN111744751A discloses a microstructure coating process for a self-matting UV coating surface. The coating includes silicone-modified polyurethane acrylate oligomer, polyurethane acrylate oligomer, reactive diluent, organic solvent, dispersant, and photoinitiator, and is cured by secondary radiation using a UV mercury lamp or EB radiation source. The prepared coating has good hardness, stain resistance, weather resistance, wear resistance, and self-matting properties.

[0004] Patent CN109641436B discloses a two-stage curable laminate technology, which sets a high-hardness resin layer and a cover layer on the surface of a resin layer containing polycarbonate resin. The cover layer may contain (meth)acrylate monomers, (meth)acrylate oligomers and surface modifiers, and is combined with photopolymerization initiators and thermal polymerization initiators to obtain higher pencil hardness, thermoforming properties and chemical resistance.

[0005] Patent CN112480807A discloses a post-UV curable formable coating liquid and a formable curable film. The system includes an acrylate prepolymer, acrylate monomers, fluorinated acrylate prepolymer, thermoplastic acrylic resin, hydroxyl acrylic resin, isocyanate curing agent, photoinitiator, and solvent. The base film can be PC, PMMA, or blends thereof. This type of technology primarily focuses on balancing formability, surface hardness, abrasion resistance, weather resistance, and stain resistance.

[0006] Patent CN103228444A discloses a polycarbonate with a hard coating, in which the hard coating film is adhered to the surface of a polycarbonate resin substrate through an adhesive layer to obtain transparency, high surface hardness, weather resistance, chemical resistance, and durability. This type of technology indicates that setting an intermediate layer or adhesive layer between the polycarbonate substrate and the surface hard layer to improve interlayer adhesion and overall performance is a common technical approach in the field.

[0007] On the other hand, EB curing technology, due to its independence from or reduced reliance on traditional photoinitiators, and its advantages such as fast curing speed, high crosslinking density, and excellent surface abrasion resistance, has also been used in hard coating systems. For example, patent CN119286323A discloses an EB-cured coating for photovoltaic backsheet films, the formulation of which includes polycarbonate acrylic resin, aliphatic polyurethane acrylic resin, multifunctional active monomers, and monofunctional active monomers, indicating that the technical solution of using oligomers with different structures and active monomers with different functionalities to form a highly crosslinked surface layer through EB curing has been found in the prior art.

[0008] However, as can be seen from the existing technologies mentioned above, current solutions mostly focus on improving the surface hardness, abrasion resistance, formability, weather resistance, or adhesion of a single hard coating, or addressing issues such as thermoforming, surface scratch resistance, and optical properties in multilayer structures. For polycarbonate sheets, simultaneously improving flame retardancy and surface abrasion resistance often faces the problem of mutual constraints between different functional components within the same coating. In particular, when flame retardant components are directly introduced into a highly cross-linked surface hardening layer, it may adversely affect the surface cross-linking structure, transparency, hardness, abrasion resistance, and interlayer compatibility; while pursuing only a highly cross-linked abrasion-resistant surface layer can easily lead to insufficient adhesion between the surface and the polycarbonate substrate, internal stress concentration, interlayer cracking, or delamination. Therefore, it is necessary to develop a composite coating structure suitable for polycarbonate sheets to improve flame retardancy while also ensuring surface abrasion resistance, and further enhance interfacial bonding strength and overall performance. Summary of the Invention

[0009] The purpose of this invention is to provide a composite coated polycarbonate sheet and its preparation method, so as to solve the problem that the surface coating of polycarbonate sheet in the prior art is difficult to simultaneously achieve flame retardant performance, surface wear resistance and interlayer bonding strength.

[0010] The present invention provides a composite coated polycarbonate sheet, comprising a polycarbonate sheet substrate, and an interface flame retardant layer and an EB wear-resistant layer sequentially disposed on the surface of the polycarbonate sheet substrate.

[0011] The interface flame retardant layer is formed by thermosetting an interface flame retardant resin. The interface flame retardant resin comprises the following components: 30wt%~40wt% of the main resin, 10wt%~30wt% of the phosphorus-containing acrylic resin, 2wt%~10wt% of the hydroxyl-containing flame retardant, 25wt%~40wt% of the dual-curing bridging resin, 1wt%~4wt% of the first additive, and a solvent. The above percentages are based on the total weight of the non-isocyanate solid components in the interface flame retardant resin. An isocyanate curing agent is added to make the NCO / OH equivalent ratio in the system 0.5~1.1.

[0012] The EB wear-resistant layer is formed by electron beam curing of EB wear-resistant layer resin; the EB wear-resistant layer resin includes the following components: 35wt%~55wt% high-functional aliphatic polyurethane acrylic resin, 5wt%~20wt% toughness and / or low shrinkage regulating aliphatic polyurethane acrylate, 10wt%~20wt% reactive silicone modified acrylic oligomer, 20wt%~35wt% acrylate monomer, and 5wt%~15wt% second auxiliary agent. The above percentages are all based on the total weight of the solid components of the EB wear-resistant layer resin.

[0013] Preferably, the host resin is an acrylic resin with hydroxyl functional groups, including MACRYNAL. ® SM 512 / 65BACX, SM 513 / 60LG, SM 510N / 65BACX, SM 685 / 55BAC, SM 2711 / 70BAC, 329960, 320863, 3220070, Uralac ® 7137 E-70, Urac ® One or more of 7134 E-57.

[0014] Preferably, the phosphorus-containing acrylic resin is a reactive phosphorus-containing acrylic oligomer, including RAYLOK. ® 1722.

[0015] Preferably, the hydroxyl-containing flame retardant is a reactive phosphorus-containing polyol flame retardant, including Exolit. TM OP 560, Exolit TM OP 552, Exolit TM OP550, Exolit TM One or more of OP1311, FCA-107, and KR-2710.

[0016] Preferably, the dual-curing bridging resin is an acrylic oligomer and / or a polyurethane acrylic oligomer containing both hydroxyl and acrylic double bonds, including EBECRYL. ®One or more of 1205, CN9062, CA-108-1, CA-108-2, and A20.

[0017] Preferably, the isocyanate curing agent is one or more of N75, 3300, 3390, 1725, 120, 3725, and 4470.

[0018] Preferably, the first additive includes one or more of adhesion promoters and leveling and wetting agents.

[0019] Preferably, the adhesion promoter is GY2600Y, SR-9051, or Dynasylan. ® One or more of GLYEO / GLYMO and TEGOAddBond 2325.

[0020] Preferably, the leveling and wetting agent is one or more of Borchi Gol 5893, DOWSIL 57, and BYK333.

[0021] Preferably, the solvent is one or more of ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, and propylene glycol methyl ether.

[0022] Preferably, the high-functional-group aliphatic polyurethane acrylic resin is one or more of EBECRYL 1290N, Agisyn230A2, Agisyn 271, Agisyn 2421, GU7500, GU7400, GU6200, 6161-100, 6195-100, 61967, 6197H, CN8885 NS, CN9110 NS, and CN9006 NS.

[0023] Preferably, the toughness and / or low shrinkage regulating aliphatic polyurethane acrylate is one or more of EBECRYL 4513, GU3480, CN969 NS, CN966J75 NS, SD1099, and SD1223.

[0024] Preferably, the reactive silicone-modified acrylic oligomer is EBECRYL. ® One of 8890, EBECRYL® 1365, GU2800Z, GU2860Z, SD1103, CN9800, 6225, and B-8116.

[0025] Preferably, the acrylate monomer is one or more of pentaerythritol hexaacrylate (DPHA), pentaerythritol triacrylate (PETA), tri(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), and tricyclodecanediethanol diacrylate (DCPDA).

[0026] Preferably, the second additive includes one or more of ultraviolet absorbers and abrasion-resistant additives.

[0027] Preferably, the ultraviolet absorber is UV400, U360, UV329, UV123, UV384, UV1164, UV5411, or Chiguard. ® One or more of 477.

[0028] Preferably, the wear-resistant additive is C784, C150, C152, or CAB-O-SIL. ® TS-720, HDK ® One of the H2O species.

[0029] This invention also provides a method for preparing composite coated polycarbonate sheets, comprising the following steps:

[0030] (1) Preparation of interfacial flame retardant layer resin: The main resin, phosphorus-containing acrylic resin, hydroxyl-containing flame retardant, dual-curing bridging resin and the first additive are added to the solvent and mixed evenly. Then, isocyanate curing agent is added to make the NCO / OH equivalent ratio in the system 0.5~1.1. After stirring evenly and vacuum degassing, the interfacial flame retardant layer resin is obtained.

[0031] (2) Preparation of EB wear-resistant layer resin: high functional group aliphatic polyurethane acrylic resin, toughness and / or low shrinkage regulating aliphatic polyurethane acrylate, reactive silicone modified acrylic oligomer, acrylate monomer and second auxiliary agent are mixed, stirred evenly and vacuum degassed to obtain EB wear-resistant layer resin.

[0032] (3) The flame retardant layer resin is coated onto the surface of the polycarbonate sheet and then subjected to heat curing treatment to obtain a polycarbonate sheet with a flame retardant layer formed on the surface.

[0033] (4) The EB wear-resistant layer resin is coated on the surface of the interface flame retardant layer, and cured by electron beam irradiation and post-treatment to obtain a composite coated polycarbonate sheet with an interface flame retardant layer and an EB wear-resistant layer on the surface.

[0034] Preferably, the thermosetting temperature in step (3) is 60℃~100℃ and the time is 10min~40min. More preferably, the thermosetting temperature is 80℃ and the time is 20min.

[0035] Preferably, the electron accelerator used for electron beam curing in step (4) has an energy of 200~500keV.

[0036] Preferably, the post-treatment temperature in step (4) is 60℃~100℃ and the time is 1h~4h. More preferably, the post-treatment temperature is 80℃ and the time is 2h.

[0037] The purpose of this invention is to provide a layered functional composite coating structure, wherein an interfacial flame-retardant layer is disposed between the polycarbonate sheet and the EB-cured wear-resistant layer, which serves to improve the flame-retardant performance of the system, enhance the adhesion to the polycarbonate substrate, and provide wetting, spreading, interfacial matching, and stress buffering for the upper EB-cured wear-resistant layer; the upper EB-cured wear-resistant layer is used to form a highly cross-linked wear-resistant surface layer, thereby achieving a better balance between flame retardancy, wear resistance, and interlayer adhesion in the resulting composite coating.

[0038] This invention also aims to control the composition and curing state of the interface flame retardant layer to form a stable composite interface with the upper EB cured wear-resistant layer, thereby avoiding problems such as disturbance of cross-linking structure, decrease in hardness, decrease in wear resistance, decrease in transparency, interlayer cracking or delamination caused by the direct introduction of flame retardant components into the surface hardening layer in the prior art.

[0039] The interfacial flame-retardant layer of this invention is not simply a base layer applied to the surface of a polycarbonate sheet, but a functional layer that combines flame-retardant, adhesion-enhancing, and interfacial transition functions. On the one hand, the interfacial flame-retardant layer improves the flame-retardant performance of the system through its phosphorus-containing structure; on the other hand, its polar groups, compliant segments, and / or residual reactive groups enhance the interfacial compatibility and adhesion between it and the polycarbonate substrate, as well as between it and the upper EB wear-resistant layer. After thermosetting, the interfacial flame-retardant layer of this invention forms a continuous film while retaining some polymerizable double bonds that can participate in subsequent electron beam curing reactions. These double bonds crosslink with the resin of the upper EB wear-resistant layer during the subsequent EB curing process, forming a physical and / or chemical composite interface between the two layers.

[0040] Beneficial effects

[0041] (1) The present invention arranges the flame retardant function mainly in the flame retardant layer at the interface close to the polycarbonate substrate, and arranges the wear resistance function mainly in the upper EB cured wear resistance layer. This avoids the problems caused by the direct introduction of flame retardant components into the highly cross-linked surface hardening layer, such as disturbance of the surface cross-linking structure, decrease in hardness, decrease in wear resistance and adverse effects on transparency. This achieves the layered decoupling of flame retardant function and wear resistance function.

[0042] (2) The interface flame retardant layer of the present invention not only plays a flame retardant role, but also has the functions of adhesion enhancement, wetting and spreading, interface matching and stress buffering, so that it forms a more stable bond relationship with the polycarbonate substrate and with the upper EB cured wear-resistant layer; by controlling the composition and curing state of the interface flame retardant layer, it is beneficial to form molecular chain penetration and entanglement between the two layers, thereby significantly improving the interlayer bonding strength.

[0043] (3) The EB-cured wear-resistant layer of the present invention uses a specific structure of oligomers and active monomers with different functionalities to synergistically construct a highly cross-linked surface layer, which can effectively improve surface hardness and wear resistance. At the same time, under the transition effect of the interfacial flame retardant layer, the internal stress concentration between the highly cross-linked surface layer and the polycarbonate substrate can be reduced, reducing the risk of cracking and delamination. In addition, EB curing has the characteristics of fast curing speed and high cross-linking efficiency, which is beneficial to improving the surface performance of the material.

[0044] (4) Compared with setting a flame retardant layer or a wear-resistant layer separately, the present invention achieves a better overall balance in terms of flame retardant performance, surface wear resistance and interlayer adhesion of polycarbonate sheets through the composite structure design of interface flame retardant layer / EB wear-resistant layer, and is therefore more suitable for application scenarios with high requirements for flame retardancy, surface wear resistance and interlayer bonding performance. Detailed Implementation

[0045] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0046] Example 1

[0047] The resin formulation for the interface flame retardant layer is as follows: main resin (35wt%), phosphorus-containing acrylic resin (25wt%), hydroxyl-containing flame retardant (4wt%), dual-curing bridging resin (35wt%), additives (1wt%), and solvent (accounting for 25wt% of total solids).

[0048] The main resin is MACRYNAL ® SM 685 / 55BAC, the phosphorus-containing acrylic resin is RAYLOK. ® 1722, the hydroxyl-containing flame retardant is Exolit. TM OP 552, the dual-curing bridging resin is EBECRIL. ® 1205, the isocyanate curing agent is N75, and the NCO / OH equivalent ratio in the system is controlled at 0.65; the additives are a mixture of adhesion promoter Dynasylan® GLYEO and wetting agent BYK333 in a mass ratio of 1:1, and the solvent is a mixture of butyl acetate and propylene glycol methyl ether acetate in a mass ratio of 1:1.

[0049] The EB wear-resistant layer resin formulation is as follows: high-functional aliphatic polyurethane acrylic resin (45wt%), toughness / low shrinkage regulating aliphatic polyurethane acrylate (10wt%), reactive silicone modified acrylic oligomer (10wt%), acrylate monomer (30wt%) and additives (5wt%).

[0050] The high-functionality aliphatic polyurethane acrylate resin is EBECRYL® 1290N, and the toughness / low shrinkage regulating aliphatic polyurethane acrylate is EBECRYL. ® 4513, the reactive silicone-modified acrylic oligomer is EBECRYL. ® 8890, the acrylate monomers are a mixture of DPHA and PETA in a mass ratio of 3:1, and the additives are UV absorber UV400 and abrasion resistant additive CAB-O-SIL. ® TS-720 is a mixture in a mass ratio of 1:3.

[0051] The above-mentioned interface flame retardant layer resin was coated onto the surface of the PC sheet and heat-cured at 80°C for 20 minutes to obtain a polycarbonate sheet with an interface flame retardant layer on the surface; then the above-mentioned EB wear-resistant layer resin was coated onto the surface of the interface flame retardant layer, cured by electron beam irradiation with an electron accelerator energy of 300keV, and post-treated at 80°C for 2 hours to obtain a composite coated polycarbonate sheet.

[0052] Example 2

[0053] Except for adjusting the proportion of the main resin to 30wt% and the proportion of phosphorus-containing acrylic resin to 30wt% in Example 1, the rest is the same as in Example 1.

[0054] Example 3

[0055] Except for adjusting the proportion of the main resin in Example 1 to 30wt% and the proportion of the dual-curing bridging resin to 40wt%, the rest is the same as in Example 1.

[0056] Example 4

[0057] Except for adjusting the proportion of the dual-curing bridging resin in Example 1 to 30wt% and the proportion of the main resin to 40wt%, everything else is the same as in Example 1.

[0058] Example 5

[0059] Except for adjusting the proportion of hydroxyl-containing flame retardant in Example 1 to 6 wt% and the proportion of main resin to 33 wt%, the rest is the same as in Example 1.

[0060] Example 6

[0061] In addition to the hydroxyl-containing flame retardant Exolit from Example 1TM OP 552 replaced with Exolit TM Except for OP 560, the rest is the same as in Example 1.

[0062] Example 7

[0063] In addition to the dual-curing bridging resin EBECRYL in Example 1 ® Except for replacing 1205 with CN9062, the rest is the same as in Example 1.

[0064] Example 8

[0065] In addition to the dual-curing bridging resin EBECRYL in Example 1 ® Except for replacing 1205 with A20, the rest is the same as in Example 1.

[0066] Example 9

[0067] In addition to the main resin MACRYNAL in Example 1 ® Except for replacing SM 685 / 55BAC with Uralac® 7137 E-70, the rest is the same as in Example 1.

[0068] Example 10

[0069] In addition to the main resin MACRYNAL in Example 1 ® Except for replacing SM 685 / 55BAC with SM512 / 65BACX, everything else is the same as in Example 1.

[0070] Example 11

[0071] Except for replacing the isocyanate curing agent N75 in Example 1 with 3390 and adjusting the NCO / OH equivalent ratio to 0.75, everything else is the same as in Example 1.

[0072] Example 12

[0073] In addition to the adhesion promoter Dynasylan in Example 1 ® Except for replacing GLYEO with TEGO AddBond 2325, everything else is the same as in Example 1.

[0074] Example 13

[0075] In addition to the high-functionality aliphatic polyurethane acrylic resin EBECRYL from Example 1 ® Except for replacing 1290N with CN8885 NS, everything else is the same as in Example 1.

[0076] Example 14

[0077] In addition to the high-functionality aliphatic polyurethane acrylic resin EBECRYL from Example 1 ® Except for replacing 1290N with Agisyn 230A2, everything else is the same as in Example 1.

[0078] Example 15

[0079] In addition to the toughness / low shrinkage modulating aliphatic polyurethane acrylate EBECRYL in Example 1 ® Except for replacing 4513 with CN969 NS, the rest is the same as in Example 1.

[0080] Example 16

[0081] In addition to the toughness / low shrinkage modulating aliphatic polyurethane acrylate EBECRYL in Example 1 ® Except for replacing 4513 with SD1099, the rest is the same as in Example 1.

[0082] Example 17

[0083] In addition to the reactive silicone-modified acrylic oligomer EBECRYL from Example 1 ® 8890 replaced with EBECRYL ® 1365, and its proportion was adjusted to 15wt%, while the proportion of acrylic monomer was adjusted to 25wt%, otherwise it was the same as in Example 1.

[0084] Example 18

[0085] In addition to the reactive silicone-modified acrylic oligomer EBECRYL from Example 1 ® Except for replacing 8890 with SD1103, the rest is the same as in Example 1.

[0086] Example 19

[0087] Except for replacing the DPHA and PETA mixture in Example 1 at a mass ratio of 3:1 with a mixture of DPHA and THEICTA at a mass ratio of 2:1, everything else is the same as in Example 1.

[0088] Example 20

[0089] Except for replacing the DPHA and PETA mixture in Example 1 at a mass ratio of 3:1 with a mixture of DPHA and DCPDA at a mass ratio of 2:1, everything else is the same as in Example 1.

[0090] Example 21

[0091] Except for replacing the ultraviolet absorber UV400 in Example 1 with UV384, everything else is the same as in Example 1.

[0092] Example 22

[0093] In addition to the wear-resistant additive CAB-O-SIL in Example 1 ® TS-720 replaced with HDK ® Except for H20, everything else is the same as in Example 1.

[0094] Example 23

[0095] Except for adjusting the thermosetting conditions of the interface flame retardant layer in Example 1 to 90°C and 15 min, the rest is the same as in Example 1.

[0096] Example 24

[0097] Except for adjusting the electron beam curing energy in Example 1 to 400keV, everything else is the same as in Example 1.

[0098] Example 25

[0099] Except for adjusting the post-processing conditions in Example 1 to 90°C and 1 hour, the rest is the same as in Example 1.

[0100] Comparative Example 1

[0101] Without setting an interface flame retardant layer, the EB wear-resistant layer resin from Example 1 was directly coated onto the surface of the PC sheet, cured by electron beam irradiation (electron accelerator energy 300keV), and post-treated at 80°C for 2 hours to obtain the comparative sample.

[0102] Comparative Example 2

[0103] The interface flame-retardant resin from Example 1 was applied to the surface of the PC sheet and heat-cured at 80°C for 20 minutes to obtain the comparative sample. No EB wear-resistant layer was prepared.

[0104] Comparative Example 3

[0105] Except for removing the dual-curing bridging resin in Example 1 and adjusting the proportion of the main resin to 55wt% to make up for the formula, the rest is the same as in Example 1 to obtain the interface flame retardant layer resin; then the same EB wear-resistant layer is prepared and composited to obtain the comparative sample.

[0106] Comparative Example 4

[0107] Except for removing the phosphorus-containing acrylic resin in Example 1 and adjusting the proportion of the main resin to 50 wt% to make up the formula, the rest is the same as in Example 1 to obtain the interface flame retardant layer resin; then the same EB wear-resistant layer is prepared and compounded to obtain the comparative sample.

[0108] Comparative Example 5

[0109] Except for removing the hydroxyl-containing flame retardant in Example 1 and adjusting the proportion of the main resin to 39 wt% to make up for the formula, the rest is the same as in Example 1, and an interface flame retardant layer resin is obtained; then the same EB wear-resistant layer is prepared and compounded to obtain a comparative sample.

[0110] Comparative Example 6

[0111] Except for removing the reactive silicone-modified acrylic oligomer in Example 1 and adjusting the acrylic monomer ratio to 40 wt% to make up the formula, the rest is the same as in Example 1, and a comparative sample is obtained.

[0112] Comparative Example 7

[0113] Except for removing the toughness / low shrinkage regulating aliphatic polyurethane acrylate in Example 1 and adjusting the proportion of high-functionality aliphatic polyurethane acrylate resin to 57wt% to supplement the formulation, the rest is the same as in Example 1, and a comparative sample is obtained.

[0114] Comparative Example 8

[0115] Except that the EB wear-resistant layer was not immediately coated after the interface flame-retardant layer in Example 1 was heat-cured, but was left at room temperature for 48 hours before the upper EB wear-resistant layer was coated and cured, the rest was the same as in Example 1, and a comparative sample was obtained.

[0116] The performance testing methods for polycarbonate sheets coated with composite coatings in the examples and comparative examples are shown below:

[0117] Visible light transmittance and haze: GB / T2410-2008;

[0118] Yellowing value: GB / T 39822-2021;

[0119] Coating adhesion: ISO 2409;

[0120] Abrasion resistance (1000g, 1000 revolutions): ASTM D1044-19;

[0121] Pencil hardness: GB / T 6739-2022;

[0122] Oxygen index: ISO 4589;

[0123] Vertical burning: UL-94;

[0124] Dual 85 aging test: GB / T 2423.50-2012;

[0125] Xenon lamp aging test: GB / T 16422.2-2014 Method A Cycle 1.

[0126] Table 1. Test results of polycarbonate sheets (Examples 1-10)

[0127]

[0128] Table 2 Test results of polycarbonate sheets (Examples 11-25)

[0129]

[0130] Table 3 Test results of polycarbonate sheets (Comparative Examples 1-8)

[0131]

[0132] As shown in Tables 1-2, the composite coated polycarbonate sheets prepared in Examples 1-25 exhibit excellent performance in terms of flame retardancy, surface hardness, wear resistance, interlayer adhesion, and damp heat stability. A relatively stable composite interface is formed between the interfacial flame-retardant layer and the EB wear-resistant layer, enabling the samples to possess high adhesion and surface wear resistance in the initial state. Furthermore, they maintain a good interfacial bonding state after damp heat treatment and aging, without significant cracking, delamination, or performance degradation. This demonstrates that the present invention achieves an effective balance between flame retardancy, wear resistance, and interlayer adhesion by primarily arranging the flame-retardant function in the interfacial flame-retardant layer close to the polycarbonate substrate and primarily arranging the wear resistance function in the upper EB cured wear-resistant layer.

[0133] Comparative Example 1 lacked an interfacial flame-retardant layer, forming only an EB abrasion-resistant layer on the PC sheet surface. While exhibiting good surface hardness and abrasion resistance, the lack of an interfacial transition layer for adhesion enhancement and stress buffering resulted in poor bonding stability with the polycarbonate substrate and insufficient flame-retardant performance. Comparative Example 2 only included an interfacial flame-retardant layer. Although it showed good adhesion to the substrate and improved flame-retardant performance, the absence of an upper highly cross-linked EB abrasion-resistant layer significantly reduced surface hardness and abrasion resistance, failing to meet the requirements for high abrasion resistance applications. Comparative Example 3 lacked a dual-curing bridging resin, resulting in a lack of double bond sites between the interfacial flame-retardant layer and the EB abrasion-resistant layer to participate in the subsequent EB curing reaction. This led to insufficient interlayer composite interface formation, decreased interlayer adhesion, and increased susceptibility to interfacial failure after humid heat. Comparative Example 4 lacked phosphorus-containing acrylic resin, weakening both the flame-retardant function of the interfacial layer and its interfacial reactivity with the upper resin, resulting in decreased flame-retardant performance and overall interfacial performance. In Comparative Example 5, no hydroxyl-containing flame retardant was added. Although the system could still form a composite coating structure, the flame retardant contribution of the interfacial flame retardant layer was insufficient, resulting in a decrease in the overall flame retardant performance of the sample. In Comparative Example 6, no reactive silicone-modified acrylic oligomer was added, leading to a decrease in the surface layer's stain resistance, slip resistance, and abrasion resistance stability. In Comparative Example 7, no toughness- and / or low-shrinkage-regulating aliphatic polyurethane acrylate was added. Although the crosslinking density of the EB abrasion-resistant layer was high, the internal stress was concentrated, making the sample more prone to embrittlement, cracking, or decreased interlayer adhesion. In Comparative Example 8, the interfacial flame retardant layer was left for too long after thermosetting before the EB abrasion-resistant layer was applied. This resulted in a decrease in the reactivity and recoating window of the interfacial layer surface, leading to poorer interlayer bonding than in the examples. This indicates that timely bonding and interfacial reaction between the interfacial layer and the EB abrasion-resistant layer are crucial for obtaining excellent overall performance.

[0134] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0135] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A composite coated polycarbonate sheet, characterized in that, It includes a polycarbonate sheet substrate, and an interface flame-retardant layer and an EB wear-resistant layer sequentially disposed on the surface of the polycarbonate sheet substrate; The interface flame retardant layer is formed by thermosetting an interface flame retardant resin. The interface flame retardant resin comprises the following components: 30wt%~40wt% of a main resin, 10wt%~30wt% of a phosphorus-containing acrylic resin, 2wt%~10wt% of a hydroxyl-containing flame retardant, 25wt%~40wt% of a dual-curing bridging resin, 1wt%~4wt% of a first additive, and a solvent. All percentages are based on the total weight of the non-isocyanate solid components in the interface flame retardant resin. An isocyanate curing agent is added to make the NCO / OH equivalent ratio in the system 0.5~1.

1. The main resin is an acrylic resin with hydroxyl functional groups; the phosphorus-containing acrylic resin is a reactive phosphorus-containing acrylic oligomer; the hydroxyl-containing flame retardant is a reactive phosphorus-containing polyol flame retardant; and the dual-curing bridging resin is an acrylic oligomer and / or a polyurethane acrylic oligomer containing both hydroxyl and acrylic double bonds. The EB wear-resistant layer is formed by electron beam curing of EB wear-resistant layer resin; the EB wear-resistant layer resin includes the following components: 35wt%~55wt% high-functional aliphatic polyurethane acrylic resin, 5wt%~20wt% toughness and / or low shrinkage regulating aliphatic polyurethane acrylate, 10wt%~20wt% reactive silicone modified acrylic oligomer, 20wt%~35wt% acrylate monomer, and 5wt%~15wt% second auxiliary agent. The above percentages are all based on the total weight of the solid components of the EB wear-resistant layer resin. The flame-retardant layer resin is coated onto the surface of the polycarbonate sheet substrate and then heat-cured before the EB wear-resistant layer resin is immediately applied.

2. The composite coated polycarbonate sheet according to claim 1, characterized in that, The first additive includes one or more of adhesion promoters and leveling and wetting agents; the solvent is one or more of ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, and propylene glycol methyl ether.

3. The composite coated polycarbonate sheet according to claim 1, characterized in that, The acrylate monomer is one or more of pentaerythritol hexaacrylate, pentaerythritol triacrylate, tri(2-hydroxyethyl) isocyanurate triacrylate, and tricyclodecanediethanol diacrylate; the second additive includes one or more of ultraviolet absorbers and abrasion resistant additives.

4. A method for preparing a composite coated polycarbonate sheet as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of interfacial flame retardant layer resin: The main resin, phosphorus-containing acrylic resin, hydroxyl-containing flame retardant, dual-curing bridging resin and the first additive are added to the solvent and mixed evenly. Then, isocyanate curing agent is added to make the NCO / OH equivalent ratio in the system 0.5~1.

1. After stirring evenly and vacuum degassing, the interfacial flame retardant layer resin is obtained. (2) Preparation of EB wear-resistant layer resin: high functional group aliphatic polyurethane acrylic resin, toughness and / or low shrinkage regulating aliphatic polyurethane acrylate, reactive silicone modified acrylic oligomer, acrylate monomer and second auxiliary agent are mixed, stirred evenly and vacuum degassed to obtain EB wear-resistant layer resin. (3) The flame retardant layer resin is coated onto the surface of the polycarbonate sheet and then subjected to heat curing treatment to obtain a polycarbonate sheet with a flame retardant layer formed on the surface. (4) The EB wear-resistant layer resin is coated on the surface of the interface flame retardant layer, and cured by electron beam irradiation and post-treatment to obtain a composite coated polycarbonate sheet with an interface flame retardant layer and an EB wear-resistant layer on the surface.

5. The preparation method according to claim 4, characterized in that, The thermosetting temperature in step (3) is 60℃~100℃ and the time is 10min~40min.

6. The preparation method according to claim 4, characterized in that, The electron accelerator used for electron beam curing in step (4) has an energy of 200~500keV.

7. The preparation method according to claim 4, characterized in that, The post-processing temperature in step (4) is 60℃~100℃, and the time is 1h~4h.

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