A multi-layer impact-resistant plastic sheet and its preparation method

Abstract

This invention relates to the field of composite material technology, specifically to a multi-layer impact-resistant plastic sheet and its preparation method. The sheet uses three masterbatches as raw materials: the first masterbatch, primarily composed of block polypropylene, forms layer A; the second masterbatch, primarily composed of linear low-density polyethylene and low-density polyethylene, forms layer B; and the third masterbatch, primarily composed of cyclic olefin copolymers or special cyclic olefin copolymers, forms layer C. By precisely controlling the composite ratio and properties of the different layers, in-situ hot-pressing composite is performed using a screw extruder to obtain a multi-layer impact-resistant plastic sheet. This sheet not only possesses excellent impact resistance and flexural properties but also exhibits good surface strength and gloss. Through the rational design of the combination and composite process of each layer, the sheet meets high-strength protection requirements while also possessing high aesthetic appeal.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to a multi-layer impact-resistant plastic sheet and its preparation method. Background Technology

[0002] In modern industry, the application of impact-resistant plastic materials is becoming increasingly widespread, especially in fields such as automobiles, aerospace, construction, and protective equipment, where high strength and toughness are required. Impact-resistant plastic sheets are gradually becoming key materials. These sheets can effectively resist external impacts, preventing cracking and deformation, thus providing reliable protection. However, the impact resistance and durability of single materials are often insufficient to meet the needs of complex application scenarios. Therefore, multilayer composite structures have become one of the key research and development directions.

[0003] Traditional impact-resistant sheets often use single-layer materials (such as engineering plastics like polycarbonate and polypropylene). Although these materials possess a certain level of impact resistance, they often crack, break, or deform severely when subjected to high-energy impacts. Furthermore, the mechanical properties, weather resistance, and service life of a single material are limited by its inherent characteristics, making it difficult to maintain stable impact resistance over long-term use or in harsh environments.

[0004] To address the shortcomings of single-layer impact-resistant materials, composite material technology has received widespread attention in recent years. Multi-layer composite impact-resistant sheets, by combining various materials in a specific structure, can achieve synergistic effects between the different material properties. Rational design of the thickness, sequence, and composition of each layer can significantly improve the impact resistance, toughness, wear resistance, and fatigue resistance of the sheet.

[0005] Nevertheless, current multi-layer impact-resistant sheet designs still face several technical challenges. For example, insufficient adhesion between material layers can lead to delamination and peeling; an unreasonable layered structure design can increase sheet thickness and weight, affecting performance; and inconsistent thermal expansion coefficients of different materials can easily cause warping or delamination. Furthermore, ensuring excellent impact resistance while maintaining lightweight, low cost, and aesthetics are also pressing technical challenges that need to be addressed. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a multilayer impact-resistant plastic sheet and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a multi-layer impact-resistant plastic sheet, comprising:

[0009] Layer A: Mainly composed of block polypropylene, containing 90-97% block polypropylene, 1-8.5% propylene-based elastomer, 0.1-5% glyceryl monostearate, 0.1-5% pentaerythritol ester, 0.1-5% triphosphite, and 0.1-5% talc by weight percentage;

[0010] Layer B: Mainly composed of linear low-density polyethylene and low-density polyethylene, containing 30-65% linear low-density polyethylene, 30-65% low-density polyethylene, 1-5% polyolefin elastomer, and 0.1-3% calcium stearate by weight percentage;

[0011] Layer C: Mainly composed of cyclic olefin copolymers or special cyclic olefin copolymers, containing, by weight percentage, 61.0-94.7% cyclic olefin copolymers or special cyclic olefin copolymers, 5-20% polyethylene, 0.1-9% calcium stearate, 0.1-5% pentaerythritol ester, and 0.1-5% colorant;

[0012] The sheet material is co-extruded by a single-screw or multi-screw extruder through a multi-layer composite die, with a barrel temperature of 100-200℃ and a die pressure of 5-19MPa, and is then calendered by hot press rollers with a linear pressure of 2-8MPa.

[0013] Preferably, layer A further comprises 1-3% of a lightweight foaming agent.

[0014] Preferably, the block polypropylene is copolymerized from propylene and at least one α-olefin comonomer, wherein the α-olefin comonomer is selected from ethylene, 1-butene, 1-hexene, 1-octene, styrene, propylene / 1-octene binary copolymer, propylene / isoprene binary copolymer, ethylene / propylene / 1-octene terpolymer, or any combination of the above copolymers.

[0015] The propylene-based elastomer is a polypropylene-based elastomer copolymerized from propylene and ethylene or α-olefins.

[0016] Preferably, the B layer further comprises 10–20% lightweight foaming agent chopped glass fibers, which are of the E-glass type, with a diameter of 10–20 μm and a length of 3–4 mm.

[0017] Preferably, the linear low-density polyethylene is a copolymer of ethylene with 1-butene, 1-hexene or 1-octene, wherein the copolymer has a density of 0.915–0.940 g / cm³ and a melt flow rate of 1–3 g / 10 min (190 °C / 2.16 kg).

[0018] The low-density polyethylene is obtained by high-pressure free radical polymerization of ethylene monomers, and the low-density polyethylene has a density of 0.910–0.925 g / cm³ and a melt flow rate of 0.2–5 g / 10 min (190 ℃ / 2.16 kg).

[0019] The polyolefin elastomer is an ethylene-octene block copolymer, wherein the ethylene content is 70–80 wt% and the octene content is 20–30 wt%. The typical Mooney viscosity of the polyolefin elastomer is 23 MU (ML1+4100 ℃) and the hardness is Shore A30–90.

[0020] The calcium stearate has a density of 1.03-1.12 g / cm³ and spherical nanoparticles with a diameter of approximately 100–300 nm.

[0021] Preferably, the cyclic olefin copolymer or special cyclic olefin copolymer is a random copolymer obtained by copolymerizing a cyclic olefin monomer with a linear olefin monomer; the cyclic olefin monomer is selected from norbornene, 1,2,3,4,4a,5,8,8a-octahydro-1,4:5,8-bicyclo[4.4.0]octane or cyclopentene; the linear olefin monomer is selected from ethylene, propylene or 1-octene.

[0022] Preferably, the special cyclic olefin copolymer is a special cyclic olefin copolymer obtained by copolymerizing a cyclic olefin monomer with a comonomer containing polar functional groups.

[0023] Preferably, the board is formed by co-extrusion or composite of at least one functional layer, and each functional layer independently meets the following thickness limits according to its type in the laminated structure: Type A layer (flexible / energy-absorbing layer): single layer thickness accounts for 50%–90% of the total thickness of the composite board; Type B layer (high-strength / energy-dissipating layer): single layer thickness accounts for 5%–25% of the total thickness of the composite board; Type C layer (rigid sheath): single layer thickness accounts for 1%–10% of the total thickness of the composite board.

[0024] Preferably, the sheet material is formed by co-extrusion or composite of at least one functional layer, and the position of each layer in the structure determines its main function.

[0025] Preferably, the masterbatches in layers A, B, and C can be co-extruded and compounded in any combination of single, double, or triple layers.

[0026] Preferably, the A / B layer interface is provided with a striped interlocking structure, with a stripe width of 0.5–2 mm and a spacing of 1–5 mm. The interlocking and locking between the layers is achieved by a back pressure of 5–15 MPa through the mold core groove and the mold head outlet.

[0027] Preferably, the C layer on the surface of the sheet is hot-embossed to form a micron-scale dot matrix with an embossing dot diameter of 0.1–0.3 mm and a dot spacing of 0.5–1 mm, with a calendering line pressure of 2–8 MPa and a calendering temperature of 120–160 ℃.

[0028] The present invention also provides a method for preparing the above-mentioned multilayer impact-resistant plastic sheet, comprising the following steps:

[0029] (1) Melt the masterbatch layers A, B, and C through separate feed ports;

[0030] (2) The melt is co-extruded through a multi-layer composite die, with a barrel temperature gradient of 100-200℃ and a die pressure of 5-19 MPa;

[0031] (3) The hot press roller assembly is calendered and compounded under a linear pressure of 2-8 MPa;

[0032] (4) Cooling and shaping, traction and winding to form a layered composite plate structure with at least one of the material layers A, B and C.

[0033] Compared with the prior art, the present invention provides a multi-layer impact-resistant plastic sheet and its preparation method, which has the following beneficial effects:

[0034] This invention achieves both high energy absorption and high rigidity / toughness in the sheet material through precise design of the three-layer material ratio: In layer A, approximately 90 wt% block polypropylene (PPB) is combined with 5 wt% polyolefin elastomer (POE). POE particles first deform and absorb energy in the continuous phase of PPB, followed by plastic flow of PPB, greatly improving fracture toughness. In layer B, approximately 50 wt% linear low-density polyethylene (LLDPE) and 45 wt% low-density polyethylene (LDPE) form a rigid skeleton, and then 5 wt% POE particles are introduced at the microcrack front to induce plastic energy dissipation, balancing initial stiffness and secondary energy absorption. In layer C, approximately 80 wt% cyclic olefin copolymer (COC) imparts high modulus and scratch resistance to the surface, combined with 20 wt% polyethylene (PE) to improve interfacial toughness and achieve good bonding with layer B, resulting in a smooth and high-gloss surface. This results in an impact strength of 100 J / m² and a flexural modulus of approximately 1150. It has a strength of MPa and a surface gloss of 80 GU, with overall performance significantly better than traditional single-layer or conventional composite structures.

[0035] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the five-layer structural plate of Embodiment 1 of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0038] Unless otherwise specified, all reagents used in the embodiments of this invention are commercially available conventional reagents or raw materials, and all test methods used in the embodiments are conventional methods in the art unless otherwise specified. The specific methods for testing the mechanical properties of composite materials are as follows: impact strength is tested according to GB / T 1843-2008 standard, flexural modulus according to GB / T 9341-2008 standard, surface gloss according to GB / T 8807-1988 standard, and peel strength according to ISO 11339:2022 standard.

[0039] This invention provides a multi-layer impact-resistant plastic sheet, comprising:

[0040] Layer A: Primarily composed of block polypropylene (PPB), containing, by weight percentage: 90-97% block polypropylene (PPB), 1-8.5% propylene-based elastomer (PBE), 0.1-5% glyceryl monostearate (GMS), 0.1-5% pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid), 0.1-5% tris(2,4-di-tert-butylphenyl) phosphite, and 0.1-5% talc.

[0041] Layer B: Mainly composed of linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE), containing 30-65% LLDPE, 30-65% LDPE, 1-5% polyolefin elastomer (POE), and 0.1-3% calcium stearate by weight percentage;

[0042] Layer C: Primarily composed of cyclic olefin copolymers (COC) or special cyclic olefin copolymers (SOOC), containing, by weight percentage: 61.0-94.7% cyclic olefin copolymers (COC) or special cyclic olefin copolymers (SOOC), 5-20% polyethylene (PE), 0.1-9% calcium stearate (Ca-St), 0.1-5% pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid), and 0.1-5% colorant;

[0043] The sheet material is co-extruded by a single-screw or multi-screw extruder through a multi-layer composite die, with a barrel temperature of 100-200℃ and a die pressure of 5-19MPa, and is then calendered by hot press rollers with a linear pressure of 2-8MPa.

[0044] Preferably, layer A further comprises 1-3% of a lightweight foaming agent.

[0045] Preferably, the block polypropylene is copolymerized from propylene and at least one α-olefin comonomer, wherein the α-olefin comonomer is selected from ethylene, 1-butene, 1-hexene, 1-octene, styrene, propylene / 1-octene binary copolymer, propylene / isoprene binary copolymer, ethylene / propylene / 1-octene terpolymer, or any combination of the above copolymers;

[0046] The propylene-based elastomer is a polypropylene-based elastomer copolymerized from propylene and ethylene or α-olefins.

[0047] Preferably, the B layer further comprises 10–20% lightweight foaming agent chopped glass fibers, wherein the chopped glass fibers are of the E-glass type, with a diameter of 10–20 μm and a length of 3–4 mm.

[0048] Preferably, the linear low-density polyethylene is a copolymer of ethylene with 1-butene, 1-hexene or 1-octene, wherein the copolymer has a density of 0.915–0.940 g / cm³ and a melt flow rate of 1–3 g / 10 min (190 °C / 2.16 kg).

[0049] The low-density polyethylene is obtained by high-pressure free radical polymerization of ethylene monomers, and the low-density polyethylene has a density of 0.910–0.925 g / cm³ and a melt flow rate of 0.2–5 g / 10 min (190 ℃ / 2.16 kg).

[0050] The polyolefin elastomer is an ethylene-octene block copolymer, wherein the ethylene content is 70–80 wt% and the octene content is 20–30 wt%. The typical Mooney viscosity of the polyolefin elastomer is 23 MU (ML1+4100 ℃) and the hardness is Shore A30–90.

[0051] The calcium stearate has a density of 1.03-1.12 g / cm³ and spherical nanoparticles with a diameter of approximately 100–300 nm.

[0052] Preferably, the cyclic olefin copolymer or special cyclic olefin copolymer is a random copolymer obtained by copolymerizing a cyclic olefin monomer with a linear olefin monomer; the cyclic olefin monomer is selected from norbornene, 1,2,3,4,4a,5,8,8a-octahydro-1,4:5,8-bicyclo[4.4.0]octane or cyclopentene; the linear olefin monomer is selected from ethylene, propylene or 1-octene.

[0053] Preferably, the special cyclic olefin copolymer is a special cyclic olefin copolymer obtained by copolymerizing a cyclic olefin monomer with a comonomer containing polar functional groups.

[0054] Preferably, the board is formed by co-extrusion or composite of at least one functional layer, and each functional layer independently meets the following thickness limits according to its type in the laminated structure: Type A layer (flexible / energy-absorbing layer): single layer thickness accounts for 50%–90% of the total thickness of the composite board; Type B layer (high-strength / energy-dissipating layer): single layer thickness accounts for 5%–25% of the total thickness of the composite board; Type C layer (rigid protective layer): single layer thickness accounts for 1%–10% of the total thickness of the composite board.

[0055] Preferably, the sheet material is formed by co-extrusion or composite of at least one functional layer, and the position of each layer in the structure determines its main function.

[0056] Preferably, the masterbatches in layers A, B, and C can be co-extruded and compounded in any combination of single, double, or triple layers.

[0057] Preferably, the A / B layer interface is provided with a striped interlocking structure, with a stripe width of 0.5–2 mm and a spacing of 1–5 mm, and the interlayer interlocking is achieved by a 5–15 MPa back pressure through the mold core groove and the mold head outlet.

[0058] Preferably, the C layer on the surface of the sheet is hot-embossed to form a micron-level dot matrix with an embossing dot diameter of 0.1–0.3 mm and a dot spacing of 0.5–1 mm, with a calendering line pressure of 2–8 MPa and a calendering temperature of 120–160 ℃.

[0059] The present invention also provides a method for preparing the above-mentioned multilayer impact-resistant plastic sheet, comprising the following steps:

[0060] (1) Melt the masterbatch layers A, B, and C through separate feed ports;

[0061] (2) The melt is co-extruded through a multi-layer composite die, with a barrel temperature gradient of 100-200℃ and a die pressure of 5-19 MPa;

[0062] (3) The hot press roller assembly is calendered and compounded under a linear pressure of 2-8 MPa;

[0063] (4) Cooling and shaping, traction and winding to form a layered composite plate structure with at least one of the material layers A, B and C.

[0064] Specifically, the A-layer formulation aims to construct a high-toughness substrate, forming a rigid-toughness gradient with the rigid outer layer: POE can be dispersed in the PPB continuous phase in the form of nano / micron particles, undergoing elastic deformation first under stress to absorb impact energy, and then the PPB phase undergoes plastic deformation, significantly improving fracture toughness; GMS, as an internal lubricant, can improve the lubricity of the PPB / POE phase interface, promote melt flow and forming, and at the same time, trace amounts of GMS form a lubricating layer at the interface, mitigating the effect of stress concentration.

[0065] In layer B, LDPE exhibits high yield elongation, enabling it to withstand considerable deformation energy under macroscopic loading. LDPE provides stable morphology and initial stiffness, and the combination of the two forms a broad-spectrum energy dissipation platform. POE forms a dispersed phase within the PE matrix; during microcrack formation, POE particles can induce plastic flow and hinder crack propagation, significantly improving impact strength. (Optional) The chopped glass fibers are of E-glass type, approximately 10–20 μm in diameter and 3–4 mm in length, and are dispersed in the matrix after treatment with a silane coupling agent to enhance stiffness and crack bridging ability.

[0066] The COC and SOOC materials in the C layer have high glass transition temperatures, making them ideal as rigid surface layers. They exhibit high flexural modulus and excellent surface smoothness at room temperature. 5–20 wt% PE improves the toughness of COC and enhances interfacial adhesion with the B layer. A uniform transition zone is formed through melt co-extrusion, reducing interfacial stress concentration.

[0067] In the specific preparation process, three different functional masterbatches are selected as raw materials according to product design requirements: low-density polyethylene masterbatch (providing impact resistance), block polypropylene masterbatch (providing flexural strength), and cyclic olefin copolymer masterbatch (providing strength and surface gloss). These masterbatches undergo pretreatment before use to ensure that their particles are uniform, have good flowability, and meet the requirements of subsequent production processes.

[0068] First, the three masterbatches are fed into different inlets of the three-screw extruder. The flow rate, temperature, and feeding method of each masterbatch are precisely controlled according to its characteristics and actual needs. The structural design of the three-screw extruder enables it to effectively control the melting process and promote the uniform mixing of various raw materials.

[0069] Because different masterbatches have different melting temperatures, the temperature in each heating zone of the three-screw extruder is precisely controlled according to the characteristics of each material.

[0070] In the latter part of the extruder, the molten masterbatch is formed into a multi-layer structure through a specially designed die. The material of each layer is arranged sequentially according to a predetermined ratio and order to ensure that the function of each layer in the sheet is independent and rational. At this time, the masterbatch of layers A, B, and C are arranged alternately, giving the sheet different functional characteristics.

[0071] In the die area, the three materials are bonded together at high temperature through a hot-pressing process. A high-pressure extruder ensures that the different functional layers are tightly bonded under the influence of temperature and pressure, forming a stable multilayer composite board. The materials are tightly bonded together through intermolecular interactions.

[0072] The extruded sheet is rapidly cooled by a cooling system to help it solidify and take shape quickly. Precise control of the cooling rate and temperature is crucial during this process; cooling too quickly or too slowly can lead to uneven material properties or deformation. After cooling, the sheet gradually hardens, ensuring that the functions at different levels are fully realized.

[0073] The cooled sheet exhibits a high gloss finish, with layer A providing excellent impact resistance, layer B providing bending resistance, and layer C imparting high strength and surface gloss to the overall sheet. This preparation method effectively achieves a composite of three functional materials, ensuring the superior performance of the multilayer sheet in terms of strength, toughness, and gloss.

[0074] Description of raw materials used in the embodiments of this invention:

[0075] Layer A masterbatch:

[0076] PPB: M02D-G, random copolymer of propylene / 1-octene, MFR≈26 g / 10 min; Supplier: Sinopec Yangzi Petrochemical Co., Ltd.

[0077] PBE: Vistamaxx™ series, a polypropylene-based elastomer copolymerized from propylene and ethylene or other α-olefins, Mooney ≈ 23 MU; Supplier: ExxonMobil;

[0078] GMS: Glyceryl monostearate; Supplier: Changzhou Kesai Chemical Co., Ltd.

[0079] Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) ester: Irganox® 1010 pentaerythritol ester antioxidant, supplier: BASF;

[0080] Tris(2,4-di-tert-butylphenyl) phosphite: P-168, Supplier: Yashi;

[0081] Nano talc: Particle size <1μm; Supplier: Shanghai Sanmei;

[0082] Foaming agent: Azodicarbonamide; Supplier: Haili Chemical.

[0083] B-layer masterbatch:

[0084] LLDPE: 7050HJ, Supplier: Sinopec Zhenhai Refining & Chemical Co., Ltd.;

[0085] LDPE: ZH220 (MFR≈2 g / 10 min), Supplier: China Petroleum & Chemical Corporation;

[0086] POE: AFFINITY™ GA1900 (Mooney≈23 MU; Shore A 30–90), Supplier: DowChemical;

[0087] Ca-St: Spherical Nanoscale Calcium Stearate: Hydrobrite™ 850; Supplier: Milliken & Co.;

[0088] Chopped glass fiber: Advantex® 9703, E-glass chopped glass fiber, supplier: Owens Corning Composites;

[0089] C-layer masterbatch:

[0090] COC: OPAS® COC, Supplier: Polyplastics Co., Ltd.

[0091] PE:HDPE:LLDPE = 1:1, Supplier: Dowlex™ / Sinopec Zhenhai;

[0092] Ca-St: Hydrobrite™ 850;

[0093] Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) ester: Irganox® 1010;

[0094] Colorant: RTP masterbatch.

[0095] Example 1: Five-layer structural panel

[0096] 1. Raw materials and ingredients

[0097] Layer A masterbatch:

[0098] PPB: 2.79 kg, PBE: 0.06 kg, GMS: 0.0225 kg; Pentaerythritol ester antioxidant: 0.0225 kg; Tris(2,4-di-tert-butylphenyl) phosphite: 0.0225 kg; Talc: 0.0225 kg; Foaming agent: 0.06 kg;

[0099] B-layer masterbatch:

[0100] LLDPE (melting point ≈ 120 ℃, MFR 2.16 g / 10 min) 2.0 kg; LDPE (MFR ≈ 2 g / 10 min) 2.0 kg; POE (Mooney ≈ 23 MU; Shore A 30–90) 0.1 kg; spherical nano-calcium stearate (particle size ≈ 200 nm) 0.02 kg; E-glass chopped glass fibers (diameter ≈ 13 μm, length 3–4 mm) 0.8 kg;

[0101] C-layer masterbatch:

[0102] COC (Tg≈138 ℃, density≈1.02 g / cm³) 2.0 kg; PE 0.5 kg; Ca-St: 0.03 kg;

[0103] Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) ester: 0.02 kg; colorant 0.1 kg.

[0104] 2. Secondary granulation process

[0105] Drying: A / C layer vacuum dried at 80 ℃ for 4 h; B layer glass fiber and Ca–St dried at 100 ℃ for 2 h.

[0106] Mixing: Mix the raw materials of each layer according to the following proportions (Layer A: PPB 90–97%, POE 1–8.5%, other additives not exceeding 10% in total; Layer B: LLDPE 30–55%, LDPE 30–60%, POE 1–9%, Ca–St 0.1–3%, glass fiber 10–20%; Layer C: COC61–94.7%, PE 5–20%, Ca–St 0.1–9%, antioxidants and color masterbatch not exceeding 10% in total) for 5 minutes.

[0107] Twin-screw extrusion:

[0108] Layer A: 150 / 155 / 160 / 165 ℃, die head 160 ℃, screw 200 rpm;

[0109] Layer B: 130 / 140 / 150 / 155 ℃, die head 155 ℃, screw 180 rpm;

[0110] Layer C: 150 / 160 / 170 / 175 ℃, die head 175 ℃, screw 160 rpm;

[0111] Underwater pelleting, followed by drying at 60 ℃ for 2 h.

[0112] 3. Five-layer co-extrusion molding and shaping

[0113] Three-screw extruder: barrel 140–165 ℃, die 165 ℃, screw 150 rpm; feed sequence A / B / C.

[0114] The co-extrusion die forms a five-layer structure (A / B / C / B / A); the hot press roll assembly (140 ℃, 5 MPa) calenders and sets the shape; the water-cooled roll cools the roll to ~25 ℃ and then rewinds it.

[0115] 4. Product Structure and Performance

[0116] Thickness: 1.5 mm (C / B / A / B / C = 0.1 / 0.2 / 0.9 / 0.2 / 0.1 mm);

[0117] Impact strength: 105 J / m² (GB / T 1843-2008), which is significantly improved compared to the traditional conventional three-layer PP / PE composite board (approximately 50–70 J / m²);

[0118] Flexural modulus: 1200 MPa;

[0119] Surface gloss: 85 GU; Gardner has good scratch resistance;

[0120] Peel strength: 5.1 N / mm.

[0121] Example 2: Three-layer structural panel

[0122] 1. Raw materials and ingredients

[0123] Layer A Masterbatch: PPB: 1.5 kg; POE: 0.1 kg; GMS: 0.05 kg; Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxycinnamic acid) ester: 0.05 kg; Tris(2,4-di-tert-butylphenyl) phosphite: 0.05 kg; Talc: 0.05 kg;

[0124] Layer B masterbatch: LLDPE: 1.5 kg; LDPE: 1.0 kg; POE: 0.05 kg; Ca–St: 0.02 kg

[0125] C-layer masterbatch: COC: 1.0 kg; PE: 0.3 kg; pentaerythritol ester antioxidant: 0.02 kg; colorant: 0.03 kg.

[0126] 2. Secondary granulation process

[0127] Drying: Same as in Example 1;

[0128] Mixing: Stir separately for 5 minutes;

[0129] Granulation parameters:

[0130] Layer A: 150 / 155 / 160 / 165 ℃, 160 ℃, 200 rpm;

[0131] Layer B: 130 / 140 / 150 / 155 ℃, 155 ℃, 180 rpm;

[0132] Layer C: 150 / 160 / 170 / 175 ℃, 175 ℃, 160 rpm;

[0133] Divide underwater and dry at 60 ℃ for 2 h.

[0134] 3. Three-layer co-extrusion molding and shaping

[0135] Three-screw extrusion: 140–165 ℃, 165 ℃, 150 rpm;

[0136] A / B / C sequential co-extrusion; hot press rollers at 140 ℃ and 5 MPa; water-cooled winding.

[0137] 4. Product Structure and Performance

[0138] Thickness: 1.2 mm (A / B / C = 0.8 / 0.3 / 0.1 mm);

[0139] Impact strength: 110 J / m², flexural modulus: 1150 MPa, surface gloss: 80 GU, peel strength: 5.3 N / mm.

[0140] Example 3: Double-layer structural panel

[0141] 1. Raw materials and ingredients

[0142] B-layer masterbatch: LLDPE: 3.0 kg; LDPE: 1.0 kg; Ca–St: 0.1 kg; E-glass chopped glass fiber: 0.5 kg;

[0143] C-layer masterbatch: COC: 2.0 kg; PE: 0.6 kg; pentaerythritol ester antioxidant: 0.04 kg; colorant: 0.06 kg.

[0144] 2. Secondary granulation process

[0145] Drying: Layer B 80 ℃ × 4 h; Layer C 100 ℃ × 2 h;

[0146] Mixing: Stir for 5 minutes;

[0147] Granulation:

[0148] Layer B: 150 / 155 / 160 / 165 ℃, 160 ℃, 200 rpm;

[0149] Layer C: 130 / 140 / 150 / 155 ℃, 155 ℃, 180 rpm;

[0150] Divide underwater and dry at 60 ℃ for 2 h.

[0151] 3. Double-layer co-extrusion molding and shaping

[0152] Twin-screw extrusion: 135–160 ℃, 160 ℃, 140 rpm;

[0153] Hot press roller at 135 ℃ and 4 MPa; water-cooled winding.

[0154] 4. Product Structure and Performance

[0155] Thickness: 1.0 mm (A / B = 0.5 / 0.5 mm);

[0156] Impact strength: 109 J / m², flexural modulus: 1180 MPa, surface gloss: 82 GU, surface scratch resistance: no obvious scratches, peel strength: 5.2 N / mm.

[0157] Comparative Example 1: Traditional five-layer PP / PE / PP / PE / PP composite board

[0158] 1. Raw material formula

[0159] Surface layer: Homopolymer polypropylene (PP) masterbatch – 100 parts by weight

[0160] Transition layer: Linear low-density polyethylene (LLDPE) masterbatch – 100 parts by weight

[0161] Intermediate energy-absorbing layer: Homopolymer polypropylene (PP) masterbatch – 100 parts by weight

[0162] Transition layer: Linear low-density polyethylene (LLDPE) masterbatch – 100 parts by weight

[0163] Bottom skin layer: Homopolymer PP masterbatch – 100 parts by weight

[0164] 2. Secondary granulation

[0165] Each layer of masterbatch is dried (80℃×3–4h) and then directly enters the co-extrusion system;

[0166] 3. Co-extrusion molding and finishing

[0167] The five-layer mold head configuration is as follows: PP / LLDPE / PP / LLDPE / PP; the remaining processes are the same as in "Comparative Example 1";

[0168] 4. Product Structure and Performance

[0169] Thickness ratio: PP / PE / PP / PE / PP = 0.2 / 0.2 / 0.7 / 0.2 / 0.2 mm, total thickness 1.5 mm;

[0170] Impact strength: 90 J / m²

[0171] Flexural modulus: 900 MPa

[0172] Surface gloss: 75 GU

[0173] Peel strength: 4.5 N / mm

[0174] Comparative Example 2: Traditional three-layer PP / PE composite board

[0175] 1. Raw material formula

[0176] Surface layer: Homopolymer polypropylene (PP) masterbatch – 100 parts by weight

[0177] Intermediate energy-absorbing layer: Linear low-density polyethylene (LLDPE) masterbatch – 100 parts by weight

[0178] Bottom skin layer: Homopolymer PP masterbatch – 100 parts by weight

[0179] 2. Secondary granulation

[0180] Each layer of masterbatch is dried (80℃×3–4h) and then directly enters the co-extrusion system;

[0181] 3. Co-extrusion molding and shaping

[0182] Twin-screw or triple-screw co-extrusion:

[0183] The temperature range is approximately 180–200℃ (PP) / 150–170℃ (PE), and the screw speed is approximately 150–200 rpm;

[0184] Die head and hot press roller: The die head is designed with a three-layer structure: top and bottom layers of PP, and center layer of LLDPE;

[0185] The temperature of the hot press roller is approximately 150–160℃, and the linear pressure is 3–5MPa.

[0186] Cooling system: water tank or air cooling; traction speed control to prevent warping.

[0187] 4. Product Structure and Performance

[0188] The thickness ratio of the three layers is approximately PP:PE:PP ≈ 1:1:1, with a total thickness of about 1.5–2.0 mm.

[0189] Impact strength: 80 J / m2, flexural modulus: 950 MPa, surface gloss: 70 GU, peel strength: 3.8 N / mm.

[0190] Comparative Example 3: Traditional Two-Layer PP / PE Composite Board

[0191] 1. Raw material formula

[0192] Surface layer: Homopolymer polypropylene (PP) masterbatch – 100 parts by weight

[0193] Bottom energy-absorbing layer: Linear low-density polyethylene (LLDPE) masterbatch – 100 parts by weight

[0194] 2. Secondary granulation

[0195] Each layer of masterbatch is dried (80 ℃ × 3–4 h) and then directly enters the co-extrusion system;

[0196] 3. Co-extrusion molding and shaping

[0197] Twin-screw co-extrusion: Temperature range 180–200 ℃ (PP) / 150–170 ℃ (PE), screw speed 150 rpm;

[0198] Die head: Two-layer structure, PP / LLDPE;

[0199] Hot press roller: 150 ℃, 3 MPa; water-cooled winding;

[0200] 4. Product Structure and Performance

[0201] Thickness ratio: PP : PE = 0.5 : 1.0 mm, total thickness 1.5 mm;

[0202] Impact strength: 70 J / m²

[0203] Flexural modulus: 800 MPa

[0204] Surface gloss: 65 GU

[0205] Peel strength: 2.5 N / mm. The above provides a detailed description of the multi-layer impact-resistant plastic sheet, its preparation method, and its manufacturing process provided in the embodiments of the present invention. Specific embodiments have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the embodiments are merely to help understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0206] Table 1. Mechanical property test data for each embodiment and comparative example

[0207]

[0208] The following conclusions can be drawn from the test data in Table 1: By comparing Example 1 (five layers), Example 2 (three layers), Example 3 (two layers) and Comparative Example 1 (five layers), Comparative Example 2 (three layers), and Comparative Example 3 (two layers), it can be concluded that: compared with the plastic sheets commonly used in the prior art, the multi-layer impact-resistant plastic sheet prepared by the present invention has significantly higher strength, toughness, gloss and peel strength.

[0209] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-layer impact-resistant plastic sheet, characterized in that: include: Layer A: Mainly composed of block polypropylene, containing 90-97% block polypropylene, 1-8.5% propylene-based elastomer, 0.1-5% glyceryl monostearate, 0.1-5% pentaerythritol ester, 0.1-5% triphosphite, and 0.1-5% talc by weight percentage; Layer B: Mainly composed of linear low-density polyethylene and low-density polyethylene, containing 30-65% linear low-density polyethylene, 30-65% low-density polyethylene, 1-5% polyolefin elastomer, and 0.1-3% calcium stearate by weight percentage; Layer C: Mainly composed of cyclic olefin copolymers or special cyclic olefin copolymers, containing, by weight percentage, 61.0-94.7% cyclic olefin copolymers or special cyclic olefin copolymers, 5-20% polyethylene, 0.1-9% calcium stearate, 0.1-5% pentaerythritol ester, and 0.1-5% colorant; The sheet material is co-extruded by a single-screw or multi-screw extruder through a multi-layer composite die, with a barrel temperature of 100-200℃ and a die pressure of 5-19MPa, and is then calendered by hot press rollers with a linear pressure of 2-8MPa.

2. The multi-layer impact-resistant plastic sheet as described in claim 1, characterized in that: Layer A further comprises 1-3% of a lightweight foaming agent.

3. The multi-layer impact-resistant plastic sheet as described in claim 1, characterized in that: The block polypropylene is copolymerized from propylene and at least one α-olefin comonomer, wherein the α-olefin comonomer is selected from ethylene, 1-butene, 1-hexene, 1-octene, styrene, propylene / 1-octene binary copolymer, propylene / isoprene binary copolymer, ethylene / propylene / 1-octene terpolymer, or any combination of the above copolymers. The propylene-based elastomer is a polypropylene-based elastomer copolymerized from propylene and ethylene or α-olefins.

4. The multi-layer impact-resistant plastic sheet as described in claim 1, characterized in that: The B layer further comprises 10–20% chopped glass fibers, which are of the E-glass type, with a diameter of 10–20 μm and a length of 3–4 mm.

5. The multi-layer impact-resistant plastic sheet as described in claim 1, characterized in that: The linear low-density polyethylene is a copolymer of ethylene with 1-butene, 1-hexene or 1-octene, the copolymer having a density of 0.915–0.940 g / cm³ and a melt flow rate of 1–3 g / 10 min at 190°C and a load of 2.16 kg. The low-density polyethylene is obtained by high-pressure free radical polymerization of ethylene monomers. The low-density polyethylene has a density of 0.910–0.925 g / cm³ and a melt flow rate of 0.2–5 g / 10 min at 190°C and 2.16 kg load. The polyolefin elastomer is an ethylene-octene block copolymer, wherein the ethylene content is 70–80 wt% and the octene content is 20–30 wt%. The polyolefin elastomer has a Shore A hardness of 30–90 and a typical Mooney viscosity of 23 MU at ML1+4 100°C. The calcium stearate has a density of 1.03-1.12 g / cm³ and spherical nanoparticles with a diameter of 100-300 nm.

6. The multi-layer impact-resistant plastic sheet as described in claim 1, characterized in that: The cyclic olefin copolymer or special cyclic olefin copolymer is a random copolymer obtained by copolymerizing cyclic olefin monomers with linear olefin monomers; the cyclic olefin monomers are selected from norbornene, 1,2,3,4,4a,5,8,8a-octahydro-1,4:5,8-bicyclo[4.4.0]octane or cyclopentene; the linear olefin monomers are selected from ethylene, propylene or 1-octene.

7. The multi-layer impact-resistant plastic sheet as described in claim 1, characterized in that: The special cyclic olefin copolymer is a special cyclic olefin copolymer obtained by copolymerizing cyclic olefin monomers with comonomers containing polar functional groups.

8. A multi-layer impact-resistant plastic sheet as described in any one of claims 1-7, characterized in that: The board is formed by co-extrusion or composite of at least one functional layer. Each functional layer independently meets the following thickness limits according to its type in the laminated structure: Type A layer: single layer thickness accounts for 50%–90% of the total thickness of the composite board; Type B layer: single layer thickness accounts for 5%–25% of the total thickness of the composite board; Type C layer: single layer thickness accounts for 1%–10% of the total thickness of the composite board.

9. A multi-layer impact-resistant plastic sheet as described in any one of claims 1-7, characterized in that: The sheet material is formed by co-extrusion or composite of at least one functional layer, and the position of each layer in the structure determines its main function.

10. A multi-layer impact-resistant plastic sheet as described in any one of claims 1-7, characterized in that: The masterbatches in layers A, B, and C can be co-extruded and compounded in any combination of single, double, or triple layers.

11. A multi-layer impact-resistant plastic sheet as described in any one of claims 1-7, characterized in that: The A / B layer interface is provided with a striped interlocking structure, with a stripe width of 0.5–2 mm and a spacing of 1–5 mm. The interlayer interlocking is achieved by the back pressure of 5–15 MPa through the mold core groove and the mold head outlet.

12. A multi-layer impact-resistant plastic sheet as described in any one of claims 1-7, characterized in that: The C layer on the surface of the sheet is hot-embossed to form a micron-level dot matrix with an embossing dot diameter of 0.1–0.3 mm and a dot spacing of 0.5–1 mm. The calendering line pressure is 2–8 MPa and the calendering temperature is 120–160 ℃.

13. A method for preparing a multilayer impact-resistant plastic sheet as described in any one of claims 1-12, characterized in that: Including the following steps: (1) Melt the masterbatch layers A, B, and C through separate feed ports; (2) The melt is co-extruded through a multi-layer composite die, with a barrel temperature gradient of 100-200℃ and a die pressure of 5-19 MPa; (3) The hot press roller assembly is calendered and compounded under a linear pressure of 2-8 MPa; (4) Cooling and shaping, traction and winding to form a layered composite plate structure with at least one of the material layers A, B and C.

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