Plastic protective plate for steel coil packaging and preparation method of plastic protective plate

Abstract

The invention discloses a plastic protective plate for steel coil packaging and a preparation method thereof, and relates to the technical field of plastic protective plates, the plastic protective plate for steel coil packaging is prepared from the following components by weight: 100 parts of PET polyester, 5-15 parts of modified glass fiber, 4-12 parts of a flexibilizer, 0.5-2 parts of a chain extender, and 0.5-1 part of an antioxidant; the plastic protective plate for packaging the steel coil has excellent environmental adaptability and mechanical property, can still keep stable performance in severe environments such as high temperature, moisture and direct sunlight, is not easy to oxidize and age, is long in service life, shows excellent impact resistance, bearing capacity and deformation resistance, can effectively absorb external impact and disperse stress, and can be used for packaging the steel coil. And all-around protection is provided for the steel coil.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic guard plates, and particularly relates to a plastic guard plate for steel coil packaging and a preparation method thereof. Background Art

[0002] With the rapid development of industrial production and logistics transportation, steel coils, as important metal raw materials, the protection during their packaging and transportation has become the focus of attention of production enterprises and the logistics industry. Traditional steel coil packaging materials mainly include wooden pallets, metal packing boxes, and paper packaging materials. These traditional packaging methods have many defects: wooden pallets are prone to deformation and moisture absorption, affecting the storage quality of steel coils; metal packing boxes have high costs and large weights, increasing the transportation burden; paper packaging materials have low strength and poor compressive resistance, making it difficult to effectively protect steel coils.

[0003] As an innovative solution for modern steel coil packaging, plastic guard plates have gradually replaced traditional packaging materials. Plastic guard plates can be classified into various types according to the matrix material, such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). Among them, PE plastic guard plates, due to their low cost, good processability, and impact resistance, are suitable for short-term and lightly loaded steel coil packaging, but they have low strength, poor heat resistance, and are prone to aging and deformation. PP plastic guard plates have excellent rigidity and chemical stability, and are particularly suitable for scenarios with higher temperature resistance requirements, but they are relatively brittle and have average impact resistance. PET plastic guard plates, with their excellent mechanical properties, good heat resistance, and dimensional stability, have become the first choice for high-end and precision steel coil packaging, although their raw material costs are relatively high. In contrast, although PVC plastic guard plates have good flame retardancy and cost advantages, they are restricted in use in scenarios with strict environmental protection requirements due to the easy generation of harmful gases.

[0004] Regarding the performance improvement of plastic guard plates, researchers have developed a variety of modification technologies. CN116945718A discloses a high-impact resistant plastic-steel end guard plate material for steel coil protection packaging and a preparation method thereof. The end guard plate material includes a tensile plastic layer, a composite fiber layer, and a rubber layer. The tensile plastic layer includes polyethylene terephthalate, an adhesive, an antioxidant, a chain extender, a rust inhibitor, and a toughening agent. The composite fiber layer includes wood fiber, phenolic resin, and paraffin. The rubber layer is disposed between the tensile plastic layer and the composite fiber layer.

[0005] Although plastic guard plates show great potential in the field of steel coil packaging, existing products still face many technical challenges. Problems such as poor impact resistance, poor aging resistance, and unsatisfactory interfacial bonding force lead to easy deformation and cracking of plastic guard plates during long-term use, making it impossible to continuously and effectively protect steel coils, seriously reducing the service life and economic value of packaging materials. These technical defects restrict the wide application of plastic guard plates in industrial production.

[0006] Therefore, it has become an urgent need to develop a plastic guard plate for steel coil packaging with excellent performance and long service life to solve the above technical problems. Summary of the Invention

[0007] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a plastic guard plate for steel coil packaging and its preparation method. The plastic guard plate for steel coil packaging of the present invention has excellent environmental adaptability and mechanical properties, can still maintain stable performance under harsh environments such as high temperature, humidity and direct sunlight, is not easy to oxidize and age, has a long service life, and exhibits excellent impact resistance, load-bearing capacity and anti-deformation performance, can effectively absorb external impacts and disperse stress, and provides comprehensive protection for steel coils.

[0008] In order to achieve the above purpose, the present invention adopts the following technical solutions: A plastic guard plate for steel coil packaging is made of the following components in parts by weight: 100 parts of PET polyester, 5 - 15 parts of modified glass fiber, 4 - 12 parts of toughening agent, 0.5 - 2 parts of chain extender, and 0.5 - 1 part of antioxidant.

[0009] Preferably, the preparation method of the modified glass fiber includes the following steps: (1) Immerse the glass fiber in an ethanol aqueous solution, add KH560, adjust the pH of the system, stir and react, filter, wash with alcohol and dry the product to obtain pretreated glass fiber; Grafting with epoxy group silane coupling agent: In an ethanol aqueous solution, KH560 (γ-glycidoxypropyltrimethoxysilane) first undergoes a hydrolysis reaction, and its methoxy group (-OCH3) is converted into an active silanol group (-Si-OH). These active silanol groups undergo a condensation reaction with the silanol groups (-Si-OH) on the surface of the glass fiber to form stable Si-O-Si covalent bonds, while retaining the epoxy group at the end of the KH560 molecule. An acidic environment (pH adjustment) promotes the hydrolysis and condensation of the silane, and finally an organic molecular layer with epoxy groups is formed on the surface of the glass fiber.

[0010] Preferably, in step (1), the volume ratio of ethanol to deionized water in the ethanol aqueous solution is 85 - 95:5 - 15; the dosage ratio of glass fiber, ethanol aqueous solution, and KH560 is 10 g:100 - 150 mL:0.5 - 1 g.

[0011] Preferably, in step (1), the pH of the system is adjusted to 4 - 5 with acetic acid; the stirring reaction conditions are stirring at 60 - 80 °C for 4 - 8 h.

[0012] (2) Add the pretreated glass fiber and 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid to DMF, add triethylamine, stir and react under a nitrogen atmosphere, filter, wash, and dry the product to obtain the intermediate glass fiber. Grafting reaction of tetramethylpiperidine acetic acid: Under the alkaline catalysis of DMF solvent and triethylamine, the epoxy groups on the surface of the pretreated glass fiber undergo ring-opening reaction. The carboxyl group (-COOH) in 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid attacks the carbon atom on the epoxy ring as a nucleophile, resulting in the ring-opening of the epoxy ring and the formation of a new covalent bond. This reaction simultaneously generates a β-hydroxy ester structure: the epoxy oxygen atom in the epoxy group obtains a proton to form a hydroxyl group (-OH), while the carboxyl group forms an ester bond (-COO-) with the epoxy carbon. The reaction result is that the tetramethylpiperidine group is successfully grafted onto the surface of the glass fiber, and at the same time, a key hydroxyl functional group is introduced.

[0013] Preferably, in step (2), the dosage ratio of the pretreated glass fiber, 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid, DMF, and triethylamine is 10 g: 1-4 g: 100-120 mL: 0.1-0.5 g.

[0014] Preferably, in step (2), the stirring reaction conditions are stirring and reacting at 90-120 °C for 8-12 h; wash the product 3-5 times with acetone, deionized water, and ethanol in sequence.

[0015] (3) Add the intermediate glass fiber and caprolactone to xylene, then add stannous octoate, heat up and react under a nitrogen atmosphere, centrifuge, wash, and dry the product to obtain the modified glass fiber.

[0016] Ring-opening polymerization of caprolactone: In the xylene solvent, stannous octoate activates the carbonyl group of the caprolactone molecule as a Lewis acid catalyst. The hydroxyl group (-OH) on the surface of the intermediate glass fiber acts as an initiator to attack the carbonyl carbon of the caprolactone molecule, resulting in the cleavage of the ester bond and the formation of a ring-opening structure. This process generates a new terminal hydroxyl group, which continues to attack the next caprolactone molecule to achieve chain growth. Through this stepwise ring-opening polymerization mechanism, the polycaprolactone molecular chain grows outward from the surface of the glass fiber, and finally, a modified glass fiber with a polycaprolactone brush-like structure is formed.

[0017] Preferably, in step (3), the dosage ratio of the intermediate glass fiber, caprolactone, xylene, and stannous octoate is 10 g: 4-12 g: 100-120 mL: 0.05-0.1 g.

[0018] Preferably, in step (3), the heating reaction conditions are to raise the reaction temperature to 100-130 °C and stir and react for 12-18 h; wash the product 2-3 times with chloroform.

[0019] Preferably, the toughening agent is ethylene-acrylate-glycidyl methacrylate copolymer; the chain extender is pyromellitic dianhydride; the antioxidant is bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite.

[0020] The present invention also claims to protect a preparation method of the plastic guard plate for steel coil packaging, which comprises the following steps: stirring the raw materials at 50-100 r / min for 5-10 min to obtain a mixed material, and melt-extruding and molding through a twin-screw extruder at 300-800 Pa, with the feeding section at 230-240 °C, the conveying section at 240-250 °C, the melting section at 260-270 °C, and the die head at 255-265 °C, to obtain the plastic guard plate for steel coil packaging.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a plastic guard plate for steel coil packaging, and through the synergistic effect of multiple components, the comprehensive performance is significantly improved. Using PET polyester as the matrix material ensures the basic strength and heat resistance of the product; adding modified glass fiber effectively improves the impact resistance and rigidity of the guard plate, significantly enhances the load-bearing capacity, avoids the deformation risk of the steel coil during transportation, and at the same time improves the dispersion of the glass fiber in the matrix and the interfacial bonding force, and improves the tensile strength, flexural strength and notched impact strength of the material; the addition of the toughening agent enables the guard plate to have good elasticity and toughness and can effectively absorb external impacts; pyromellitic dianhydride as the chain extender increases the molecular weight of PET and improves the melt strength and processing performance of the material; the hindered phenol structure in the antioxidant can provide hydrogen atoms to free radicals to terminate the chain reaction, or directly combine with active free radicals to form new relatively stable free radicals, thereby destroying any step in the free radical reaction process, playing a protective role and maintaining the stability of the appearance and mechanical properties of the material. The present invention exhibits excellent antioxidant performance through the synergistic effect of the hindered phenol structure and the hindered amine structure in the modified glass fiber, prolongs the service life of the product, and improves the environmental adaptability of the product.

[0022] 2. The present invention provides a modified glass fiber, whose performance is improved through three-step modification. In the first step, treatment with KH560 silane coupling agent grafts epoxy groups onto the surface of the glass fiber, improving the chemical activity of the glass fiber surface. In the second step, grafting of tetramethylpiperidine acetic acid not only introduces a hydroxyl ester structure onto the glass fiber surface, but also introduces a tetramethylpiperidine group with a steric hindrance effect, significantly improving the light aging resistance of the material. This hindered amine structure can decompose hydroperoxides and convert them into harmless substances; it has extremely strong free radical scavenging ability, can neutralize and stabilize free radicals, and prevent the polymer chain scission reaction initiated by free radicals; and it has a regeneration ability, that is, it can restore its own stability after the free radical scavenging reaction and continue to play a role. In the third step, ring-opening polymerization of ε-caprolactone forms polycaprolactone molecular chains on the glass fiber surface. Since polycaprolactone is a polymeric polyester with an ester bond structure similar to that of PET, it greatly improves the interfacial bonding strength between the glass fiber and the PET matrix, reduces stress concentration, and reduces the generation of microcracks inside the composite material. On the other hand, the introduction of polycaprolactone graft brings rich long-chain structures, further improving the flexibility of the product. Polar groups such as heterocycles and ester groups in the modified glass fiber promote the compatibility between the glass fiber and PET. The three-step modification acts synergistically, enabling the modified glass fiber to exhibit excellent reinforcing and toughening effects in the plastic guard plate, significantly improving the pressure resistance and impact resistance of the guard plate. Detailed implementation manners

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with embodiments. Of course, the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] Unless otherwise specified, the chemical reagents and materials in the present invention are purchased through market channels or synthesized from raw materials purchased through market channels.

[0025] The average diameter of the glass fiber is 10 μm, purchased from China National Bluestar (Group) Co., Ltd., with the product number E7CS10-03-540H; the model of the PET polyester is FR530L NC010; the model of the ethylene-acrylate-glycidyl methacrylate copolymer is AX8900.

[0026] A preparation method of a plastic guard plate for steel coil packaging includes the following steps: (1) Immerse 10 g of glass fiber in 100 - 150 mL of an ethanol aqueous solution (the volume ratio of ethanol to deionized water is 85 - 95:5 - 15), add 0.5 - 1 g of KH560, adjust the pH of the system to 4 - 5 with acetic acid, stir and react at 60 - 80 °C for 4 - 8 h, filter the product, wash it with alcohol, and dry it to obtain pretreated glass fiber; (2) Add 10 g of pretreated glass fiber and 1 - 4 g of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid to 100 - 120 mL of DMF, add 0.1 - 0.5 g of triethylamine, stir and react at 90 - 120 °C under a nitrogen atmosphere for 8 - 12 h. Filter the product, wash it 3 - 5 times successively with acetone, deionized water, and ethanol, and dry it to obtain intermediate glass fiber; (3) Add 10 g of intermediate glass fiber and 4 - 12 g of caprolactone to 100 - 120 mL of xylene, then add 0.05 - 0.1 g of stannous octanoate. Raise the reaction temperature to 100 - 130 °C under a nitrogen atmosphere and stir and react for 12 - 18 h. Centrifuge the product, wash it 2 - 3 times with chloroform, and dry it to obtain modified glass fiber; (4) Add 100 parts of PET polyester, 5 - 15 parts of modified glass fiber, 4 - 12 parts of toughening agent, 0.5 - 2 parts of chain extender pyromellitic dianhydride, and 0.5 - 1 part of antioxidant bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate. Stir at 50 - 100 r / min for 5 - 10 min to obtain a mixture. Melt and extrude it through a twin-screw extruder at 300 - 800 Pa. The feeding section is at 230 - 240 °C, the conveying section is at 240 - 250 °C, the melting section is at 260 - 270 °C, and the die head is at 255 - 265 °C to obtain the plastic guard plate for steel coil packaging.

[0027] The toughening agent is ethylene-acrylate-glycidyl methacrylate copolymer.

[0028] The following is a further description of the present invention through specific examples.

[0029] Example 1 A preparation method of a plastic guard plate for steel coil packaging includes the following steps: (1) Immerse 10 g of glass fiber in 150 mL of ethanol aqueous solution (the volume ratio of ethanol to deionized water is 90:10), add 1 g of KH560, adjust the pH of the system to 4.5 with acetic acid, stir and react at 80 °C for 4 h. Filter the product, wash it with alcohol, and dry it to obtain pretreated glass fiber; (2) Add 10 g of pretreated glass fiber and 4 g of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid to 100 mL of DMF, add 0.5 g of triethylamine, stir and react at 120 °C under a nitrogen atmosphere for 8 h. Filter the product, wash it 3 times successively with acetone, deionized water, and ethanol, and dry it to obtain intermediate glass fiber; (3) Add 10 g of intermediate glass fiber and 12 g of caprolactone to 100 mL of xylene, then add 0.1 g of stannous octanoate. Raise the reaction temperature to 130 °C under a nitrogen atmosphere and stir and react for 12 h. Centrifuge the product, wash it 2 times with chloroform, and dry it to obtain modified glass fiber; (4) Stir 1000 g of PET polyester, 150 g of modified glass fiber, 120 g of toughening agent ethylene-acrylate-glycidyl methacrylate copolymer, 20 g of chain extender pyromellitic dianhydride, and 10 g of antioxidant bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate at 80 r / min for 8 min to obtain a mixture, and melt and extrude it at 500 Pa through a twin-screw extruder. The feeding section is at 235 °C, the conveying section is at 245 °C, the melting section is at 265 °C, and the die head is at 260 °C to obtain a plastic guard plate for steel coil packaging.

[0030] Example 2 A preparation method of a plastic guard plate for steel coil packaging, comprising the following steps: (1) Immerse 10 g of glass fiber in 150 mL of ethanol aqueous solution (the volume ratio of ethanol to deionized water is 90:10), add 0.8 g of KH560, adjust the pH of the system to 4.5 with acetic acid, stir and react at 70 °C for 6 h, filter the product, wash it with alcohol, and dry it to obtain pretreated glass fiber; (2) Add 10 g of pretreated glass fiber and 3 g of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid to 100 mL of DMF, add 0.4 g of triethylamine, stir and react at 110 °C under a nitrogen atmosphere for 10 h, filter the product, wash it 3 times with acetone, deionized water, and ethanol in sequence, and dry it to obtain intermediate glass fiber; (3) Add 10 g of intermediate glass fiber and 8 g of caprolactone to 100 mL of xylene, then add 0.08 g of stannous octoate, raise the reaction temperature to 120 °C under a nitrogen atmosphere, stir and react for 14 h, centrifuge the product, wash it 2 times with chloroform, and dry it to obtain modified glass fiber; (4) Stir 1000 g of PET polyester, 120 g of modified glass fiber, 100 g of toughening agent ethylene-acrylate-glycidyl methacrylate copolymer, 15 g of chain extender pyromellitic dianhydride, and 8 g of antioxidant bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate at 80 r / min for 8 min to obtain a mixture, and melt and extrude it at 500 Pa through a twin-screw extruder. The feeding section is at 235 °C, the conveying section is at 245 °C, the melting section is at 265 °C, and the die head is at 260 °C to obtain a plastic guard plate for steel coil packaging.

[0031] Example 3 A preparation method of a plastic guard plate for steel coil packaging, comprising the following steps: (1) Immerse 10 g of glass fiber in 150 mL of ethanol aqueous solution (the volume ratio of ethanol to deionized water is 90:10), add 0.6 g of KH560, adjust the pH of the system to 4.5 with acetic acid, stir and react at 70 °C for 6 h, filter the product, wash it with alcohol, and dry it to obtain pretreated glass fiber; (2) Add 10 g of pretreated glass fiber and 2 g of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid to 100 mL of DMF, add 0.2 g of triethylamine, stir and react at 100 °C under a nitrogen atmosphere for 10 h. Filter the product, wash it 3 times successively with acetone, deionized water, and ethanol, and dry it to obtain intermediate glass fiber; (3) Add 10 g of intermediate glass fiber and 10 g of ε-caprolactone to 100 mL of xylene, then add 0.06 g of stannous octoate, raise the reaction temperature to 110 °C under a nitrogen atmosphere, stir and react for 16 h. Centrifuge the product, wash it 2 times with chloroform, and dry it to obtain modified glass fiber; (4) Add 1000 g of PET polyester, 80 g of modified glass fiber, 80 g of toughening agent ethylene-acrylate-glycidyl methacrylate copolymer, 10 g of chain extender pyromellitic dianhydride, and 6 g of antioxidant bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate to stir at 80 r / min for 8 min to obtain a mixture. Melt and extrude it through a twin-screw extruder at 500 Pa, with the feeding section at 235 °C, the conveying section at 245 °C, the melting section at 265 °C, and the die head at 260 °C to obtain a plastic guard plate for steel coil packaging.

[0032] Example 4 A preparation method of a plastic guard plate for steel coil packaging, comprising the following steps: (1) Immerse 10 g of glass fiber in 150 mL of an ethanol aqueous solution (the volume ratio of ethanol to deionized water is 90:10), add 0.5 g of KH560, adjust the pH of the system to 4.5 with acetic acid, stir and react at 60 °C for 8 h. Filter the product, wash it with alcohol, and dry it to obtain pretreated glass fiber; (2) Add 10 g of pretreated glass fiber and 1 g of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid to 100 mL of DMF, add 0.1 g of triethylamine, stir and react at 90 °C under a nitrogen atmosphere for 12 h. Filter the product, wash it 3 times successively with acetone, deionized water, and ethanol, and dry it to obtain intermediate glass fiber; (3) Add 10 g of intermediate glass fiber and 4 g of ε-caprolactone to 100 mL of xylene, then add 0.05 g of stannous octoate, raise the reaction temperature to 10 °C under a nitrogen atmosphere, stir and react for 18 h. Centrifuge the product, wash it 2 times with chloroform, and dry it to obtain modified glass fiber; (4) 1000 g of PET polyester, 50 g of modified glass fiber, 40 g of toughening agent ethylene - acrylate - glycidyl methacrylate copolymer, 5 g of chain extender pyromellitic dianhydride, and 5 g of antioxidant bis(2,4 - di - tert - butylphenyl)pentaerythritol diphosphate were stirred at 80 r / min for 8 min to obtain a mixture, which was melt - extruded and formed at 500 Pa by a twin - screw extruder. The feeding section was at 235 °C, the conveying section was at 245 °C, the melting section was at 265 °C, and the die head was at 260 °C to obtain a plastic guard plate for steel coil packaging.

[0033] Comparative Example 1 A preparation method of a plastic guard plate for steel coil packaging includes the following steps: (1) Immerse 10 g of glass fiber into 150 mL of ethanol - aqueous solution (the volume ratio of ethanol to deionized water is 90:10), add 1 g of KH560, adjust the pH of the system to 4.5 with acetic acid, stir and react at 80 °C for 4 h, filter the product, wash it with alcohol, and dry it to obtain pretreated glass fiber. (2) Add 10 g of pretreated glass fiber and 4 g of 2 - (2,2,6,6 - tetramethylpiperidin - 4 - yl)acetic acid to 100 mL of DMF, add 0.5 g of triethylamine, stir and react at 120 °C under a nitrogen atmosphere for 8 h, filter the product, wash it 3 times with acetone, deionized water, and ethanol in sequence, and dry it to obtain intermediate glass fiber. (3) 1000 g of PET polyester, 150 g of intermediate glass fiber, 120 g of toughening agent ethylene - acrylate - glycidyl methacrylate copolymer, 20 g of chain extender pyromellitic dianhydride, and 10 g of antioxidant bis(2,4 - di - tert - butylphenyl)pentaerythritol diphosphate were stirred at 80 r / min for 8 min to obtain a mixture, which was melt - extruded and formed at 500 Pa by a twin - screw extruder. The feeding section was at 235 °C, the conveying section was at 245 °C, the melting section was at 265 °C, and the die head was at 260 °C to obtain a plastic guard plate for steel coil packaging.

[0034] Comparative Example 2 A preparation method of a plastic guard plate for steel coil packaging includes the following steps: (1) Immerse 10 g of glass fiber into 150 mL of ethanol - aqueous solution (the volume ratio of ethanol to deionized water is 90:10), add 1 g of KH560, adjust the pH of the system to 4.5 with acetic acid, stir and react at 80 °C for 4 h, filter the product, wash it with alcohol, and dry it to obtain pretreated glass fiber. (2) (2)Mix 1000 g of PET polyester, 150 g of pretreated glass fiber, 120 g of toughening agent ethylene-acrylate-glycidyl methacrylate copolymer, 20 g of chain extender pyromellitic dianhydride, and 10 g of antioxidant bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate at 80 r / min for 8 min to obtain a mixed material, and melt and extrude it through a twin-screw extruder at 500 Pa. The feeding section is at 235 °C, the conveying section is at 245 °C, the melting section is at 265 °C, and the die head is at 260 °C to obtain a plastic guard plate for steel coil packaging.

[0035] Perform performance tests on the plastic guard plates prepared in Examples 1-4 and Comparative Examples 1-2. Refer to GB / T 9341-2008 "Plastics - Determination of flexural properties" to test the flexural strength; refer to GB / T 1040.2-2022 "Plastics - Determination of tensile properties - Part 2: Test conditions for moulding and extrusion plastics" to test the elongation at break; refer to GB / T 1043.1-2008 "Plastics - Determination of Charpy impact properties - Part 1: Non-instrumented impact test" to test the Charpy notched impact strength; refer to ISO4892-3-2016 "Plastics - Methods of exposure to laboratory light sources - Part 3: Fluorescent ultraviolet lamps" to conduct an ultraviolet accelerated aging experiment. Place the sample in a UVZN-320 ultraviolet lamp aging test chamber with a light source of UVA-340, a radiation energy of 0.83 W / (m 2 nm), a temperature of 70 °C. For every 4 h of light exposure, there is a 1 h gap when the light is turned off, and cycle the test for 100 h, then test the retention rates of the flexural strength and impact strength; place the sample in a YSGJS type high and low temperature and humidity aging chamber, continuously age it at a temperature of 85 °C and a humidity of 85% for 1000 h, and then test the retention rates of the flexural strength and impact strength. The specific data are shown in Table 1.

[0036] Table 1 Performance test results of plastic guard plates

[0037] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A plastic guard plate for steel coil packaging, characterized in that, It is made of the following components by weight parts: 100 parts of PET polyester, 5 - 15 parts of modified glass fiber, 4 - 12 parts of toughening agent, 0.5 - 2 parts of chain extender, 0.5 - 1 part of antioxidant; The preparation method of the modified glass fiber includes the following steps: (1) Immerse the glass fiber in an ethanol aqueous solution, add KH560, adjust the pH of the system, stir and react, filter, wash with alcohol and dry the product to obtain pretreated glass fiber; (2) Add the pretreated glass fiber and 2-(2,2,6,6 - tetramethylpiperidin - 4 - yl) acetic acid into DMF, add triethylamine, stir and react under a nitrogen atmosphere, filter, wash and dry the product to obtain intermediate glass fiber; (3) Add the intermediate glass fiber and caprolactone into xylene, then add stannous octoate, react under a nitrogen atmosphere, centrifuge, wash and dry the product to obtain modified glass fiber.

2. The plastic guard plate for steel coil packaging according to claim 1, characterized in that, In step (1), the volume ratio of ethanol to deionized water in the ethanol aqueous solution is 85 - 95:5 - 15.

3. The plastic guard plate for steel coil packaging according to claim 2, wherein In step (1), the dosage ratio of the glass fiber, ethanol aqueous solution and KH560 is 10g:100 - 150mL:0.5 - 1g.

4. The plastic guard plate for steel coil packaging according to claim 2, wherein In step (1), adjust the pH of the system to 4 - 5 with acetic acid; the stirring reaction conditions are stirring reaction at 60 - 80°C for 4 - 8h.

5. The plastic guard plate for steel coil packaging according to claim 2, characterized in that, In step (2), the dosage ratio of the pretreated glass fiber, 2-(2,2,6,6 - tetramethylpiperidin - 4 - yl) acetic acid, DMF and triethylamine is 10g:1 - 4g:100 - 120mL:0.1 - 0.5g.

6. The plastic guard plate for steel coil packaging according to claim 2, wherein In step (2), the stirring reaction conditions are stirring reaction at 90 - 120°C for 8 - 12h; wash the product with acetone, deionized water and ethanol successively for 3 - 5 times.

7. The plastic guard plate for steel coil packaging according to claim 2, wherein In step (3), the dosage ratio of the intermediate glass fiber, caprolactone, xylene and stannous octoate is 10g:4 - 12g:100 - 120mL:0.05 - 0.1g.

8. The plastic guard plate for steel coil packaging according to claim 2, wherein In step (3), the reaction conditions are to raise the reaction temperature to 100 - 130°C, stir and react for 12 - 18h; wash the product with chloroform for 2 - 3 times.

9. The plastic guard plate for steel coil packaging according to claim 1, wherein, The toughening agent is ethylene - acrylate - glycidyl methacrylate copolymer; the chain extender is pyromellitic dianhydride; the antioxidant is bis(2,4 - di - tert - butylphenyl)pentaerythritol diphosphite.

10. A preparation method of the plastic guard plate for steel coil packaging according to any one of claims 1 to 9, characterized in that, It includes the following steps: Stir the components of the plastic guard plate at 50 - 100r / min for 5 - 10min to obtain a mixture, and melt - extrude and mold it through a twin - screw extruder at 300 - 800Pa. The feeding section is 230 - 240°C, the conveying section is 240 - 250°C, the melting section is 260 - 270°C, and the die head is 255 - 265°C to obtain the plastic guard plate for steel coil packaging.

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