Graft modified PP material and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a graft modified PP material and a preparation method thereof. The graft modified PP material is prepared from the following components in parts by weight: 100 parts of polypropylene, 8 to 15 parts of alkenyl-terminated hyperbranched polymer, 0.3 to 0.7 part of initiator and 0.1 to 0.5 part of antioxidant. The alkenyl-terminated hyperbranched polymer is prepared by carrying out ring-opening reaction polymerization on terephthalic acid diglycidyl ester and ethanolamine phosphate through hydroxyl and epoxy groups, and then terminating through glycidyl methyl propionate. The prepared graft modified PP material has good flame retardant property while improving the performance retention rate of the material in a low-temperature environment, the application range of the PP material is widened, and the PP material has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a graft-modified PP material and a preparation method thereof. Background Art

[0002] Polypropylene (PP) is widely used in automotive parts, electronic housings, and other fields due to its excellent processing properties and cost advantages. However, the highly regular nature of its molecular chains leads to significant material defects. On the one hand, the mobility of the molecular segments decreases sharply at low temperatures, resulting in increased brittleness and a sharp decrease in impact strength, making it difficult to meet the requirements of use in cold regions or low-temperature operating conditions. On the other hand, PP is a flammable material, and severe melt dripping during combustion poses a fire hazard. Traditional modification techniques often fail to achieve a synergistic improvement in low-temperature toughness and flame retardancy. For example, while copolymerization or blending with toughening agents (such as POE) can improve low-temperature impact resistance, the material's rigidity is significantly reduced and its flame retardancy is further deteriorated. While the addition of halogenated flame retardants can inhibit combustion, it exacerbates low-temperature brittleness and is accompanied by the release of toxic gases. In recent years, while methods such as nanocomposite modification and reactive extrusion grafting have made some progress, they still face challenges such as uneven dispersion of functional components and weak interfacial bonding, resulting in low modification efficiency and the inability to achieve substantial performance breakthroughs.

[0003] Existing research indicates that constructing a multi-level interactive network through molecular design is an effective approach to overcoming PP's performance bottleneck. Some technologies attempt to introduce branched structures to improve molecular chain entanglement, such as using long-chain branched PP to enhance melt strength. However, these efforts have limited benefits in improving low-temperature toughness and fail to impart flame retardancy. Other studies have attempted to enhance flame retardancy by grafting phosphorus- and nitrogen-containing flame retardant groups. However, the introduction of rigid flame retardant components often exacerbates material embrittlement and can easily cause interfacial debonding at low temperatures. The key to resolving this performance dilemma is how to simultaneously construct a toughening network and a flame retardant barrier within the PP matrix through the structural design of a single functional component. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to propose a grafted modified PP material and a preparation method thereof, so as to solve the problem that the existing PP material cannot strike a balance between low temperature performance and flame retardant performance.

[0005] Based on the above purpose, the present invention provides a graft-modified PP material, comprising the following raw materials in parts by weight: polypropylene: 100 parts, terminal olefin hyperbranched polymer: 8-15 parts, initiator: 0.3-0.7 parts, antioxidant: 0.1-0.5 parts, and the preparation process of the terminal olefin hyperbranched polymer is as follows:

[0006] (1) Preparation of hyperbranched polymer: Diglycidyl terephthalate, ethanolamine phosphate, and triethylamine were added to N,N-dimethylacetamide (DMAC), heated to 60-80°C with stirring, reacted for 12-16 hours, cooled to room temperature, and then diluted hydrochloric acid was added to adjust the pH to neutral. Then, 5°C acetone was added, and the resulting precipitate was centrifuged and recrystallized from tetrahydrofuran / ether to obtain a hyperbranched polymer.

[0007] (2) Preparation of terminal olefin hyperbranched polymer: The hyperbranched polymer obtained in (1), glycidyl methacrylate, and triethylamine were added to DMAC, heated to 80-100° C. with stirring, reacted for 6-8 hours, cooled to room temperature, and then diluted hydrochloric acid was added to adjust the pH to neutral. Then, n-hexane was added, and the obtained precipitate was centrifuged, washed with petroleum ether, washed with deionized water, and freeze-dried to obtain a terminal olefin hyperbranched polymer.

[0008] Preferably, the melt index of the polypropylene is 5-12 g / 10 min.

[0009] Preferably, the initiator is benzoyl peroxide.

[0010] Preferably, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1.

[0011] Preferably, the reaction process diagram in (1) is as follows:

[0012]

[0013] The epoxy group in compound A reacts with the hydroxyl group in compound B. Compound A and compound B are continuously polymerized through ether bond connection. At the same time, after the epoxy group in compound A is ring-opened, new hydroxyl groups are formed to continue to polymerize with other epoxy groups in compound A to form a highly branched hyperbranched polymer. Moreover, by controlling the excess of compound B, this hyperbranched polymer is also a structure with terminal hydroxyl groups. In order to prove that compound A and compound B have reacted, the product is subjected to 1 H NMR, 15 N NMR and 31 PNMR was used for characterization.

[0014] Preferably, the weight ratio of diglycidyl terephthalate, ethanolamine phosphate, triethylamine, DMAC and 5°C acetone in (1) is 1:1-1.4:0.001-0.003:8-12:16-24, and dilute hydrochloric acid refers to a hydrochloric acid solution with a concentration of 10%.

[0015] Preferably, the reaction process diagram in (2) is as follows:

[0016]

[0017] The terminal hydroxyl groups of the hyperbranched polymer and the epoxy groups in compound C undergo a ring-opening reaction under the action of a catalyst. By controlling the excess of compound C, the terminal hydroxyl groups of the hyperbranched polymer are replaced by terminal olefin groups through the ring-opening reaction.

[0018] Preferably, in said (2), the weight ratio of the hyperbranched polymer, glycidyl methacrylate, triethylamine, DMAC and n-hexane is 1:0.6-0.8:0.01-0.03:8-12:16-24, and the dilute hydrochloric acid refers to a hydrochloric acid solution with a concentration of 10%.

[0019] Furthermore, the present invention also provides a method for preparing the above-mentioned graft-modified PP material, which specifically includes the following steps: adding polypropylene, terminal olefin hyperbranched polymer, initiator and antioxidant to a high-speed mixer, mixing at 2000-3000 rpm for 10-15 minutes, and then adding to a twin-screw extruder. After the material is extruded, granulated, cooled, washed with acetone, and dried, a graft-modified PP material is obtained.

[0020] Preferably, the reaction process diagram in the preparation method is as follows:

[0021]

[0022] in It is a partially enlarged schematic structure of the terminal group of the terminal olefin hyperbranched structure, and R is a terminal olefin hyperbranched polymer.

[0023] Preferably, the polypropylene is first placed in a forced air drying oven and dried at 80-90° C. for 2-4 hours.

[0024] Preferably, the parameters of the twin-screw extruder are: feeding section temperature: 160-170°C, compression section temperature: 180-200°C, homogenization section temperature: 200-220°C, die head temperature: 200-220°C, and screw speed 200-300rpm.

[0025] Beneficial effects of the present invention:

[0026] 1. In traditional PP modification technology, low-temperature toughening and flame retardant properties often present a contradictory relationship of one increasing while the other decreases. For example, although the introduction of toughening agents can improve low-temperature impact resistance, it will significantly reduce the rigidity of the material and aggravate melt dripping, resulting in deterioration of flame retardant properties; and although the addition of flame retardants inhibits combustion, it aggravates low-temperature brittleness due to the interfacial stress concentration effect of rigid particles. The present invention constructs dynamic cross-linking points in the PP matrix through the three-dimensional network structure design of hyperbranched polymers. Its branching nodes can effectively absorb impact energy and inhibit crack propagation, significantly improving the elongation at break and notched impact strength of the material at low temperatures. At the same time, the PN synergistic flame retardant system introduced in the hyperbranched structure inhibits combustion through the dual mechanisms of gas-phase free radical capture and the formation of a dense carbon layer in the condensed phase during combustion, and the entanglement of the branched network on the melt can effectively prevent melt dripping, thereby achieving synergistic optimization of flame retardant properties and low-temperature toughness.

[0027] 2. Traditional modification methods often lead to an imbalance in material properties due to the singleness of functional components. For example, excessive addition of toughening agents will lead to a sharp drop in tensile strength, while the introduction of rigid flame retardants maintains strength but sacrifices toughness. The present invention uses molecular design of hyperbranched polymers, and its branched structure can accurately regulate the crystallization behavior of PP: the branching points destroy the regular arrangement of PP molecular chains to reduce crystallinity and give the material high toughness; while the physical entanglement of the rigid benzene ring skeleton and the PP matrix maintains the tensile strength of the material. In addition, the terminal olefin groups of the hyperbranched structure form chemical bonds with the PP molecular chains through free radical grafting reactions, avoiding the phase separation problem in traditional blending modifications, and allowing the material to exhibit excellent mechanical stability over a wide temperature range. This "rigid and flexible" design concept breaks through the limitations of performance trade-offs in traditional modifications and provides a material basis for the application of PP in extreme environments.

[0028] 3. Traditional PP modification technology often faces problems of performance degradation and process fluctuations. For example, flame retardants are prone to migration and precipitation in physical blending modification, resulting in a significant decrease in the flame retardant properties of the material over time; and the multi-step chemical modification process is sensitive to reaction conditions and is prone to fluctuations in grafting rate, affecting product consistency. The present invention uses a molecular-level structural design of hyperbranched polymers to anchor the PN flame retardant unit to the three-dimensional branched network in the form of covalent bonds, forming a stable flame retardant-toughening integrated architecture. This chemical bonding method not only blocks the migration channel of the flame retardant component, ensuring the stable performance of the material during long-term use, but also inhibits the thermal motion of the PP molecular chain through the steric hindrance effect of the branching nodes, delaying the aging process of the material. In addition, the entire process adopts a halogen-free flame retardant system to avoid the release of toxic substances in traditional flame retardant processes, which meets the needs of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 For hyperbranched polymers 1 H NMR spectrum;

[0030] Figure 2 For hyperbranched polymers 15 N NMR spectrum;

[0031] Figure 3 For hyperbranched polymers 31 PNMR spectrum. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0033] The sources of the reagents and raw materials used in the examples of the present invention are as follows:

[0034] Polypropylene was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a melt index of 5-12 g / 10 min; diglycidyl terephthalate was purchased from Hangzhou Jieheng Chemical Co., Ltd. with a purity of 98%; ethanolamine phosphate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 98%; glycidyl methacrylate was purchased from Shanghai Haohong Biopharmaceutical Technology Co., Ltd. with a purity of 98%; antioxidant 1010 was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a product number of P750268 and a purity of 98%; antioxidant 168 was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 98%. Benzoyl peroxide was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 99%; bis(2,3-epoxypropyl)malonate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 98%; bis(2-hydroxyethyl)terephthalate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 95%; 1,3-dihydroxyacetone was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 99%; terephthalic acid was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 99%; p-toluenesulfonic acid was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 99%.

[0035] Example 1: A specific preparation method of a graft-modified PP material, comprising the following steps:

[0036] (1) 50 g of diglycidyl terephthalate, 50 g of ethanolamine phosphate, and 0.05 g of triethylamine were added to 400 g of DMAC, heated to 60° C. with stirring, reacted for 12 h, cooled to room temperature, and then 10% dilute hydrochloric acid was added to adjust the pH to neutral. 800 g of 5° C. acetone was then added. The resulting precipitate was centrifuged and recrystallized from tetrahydrofuran / ether to obtain a hyperbranched polymer.

[0037] (2) 80 g of the hyperbranched polymer obtained in (1), 48 g of glycidyl methacrylate, and 0.8 g of triethylamine were added to 640 g of DMAC, and the mixture was heated to 80° C. with stirring, reacted for 6 h, and cooled to room temperature. 10% dilute hydrochloric acid was added to adjust the pH to neutral, and 1.28 kg of n-hexane was added. The resulting precipitate was centrifuged, washed with petroleum ether, washed with deionized water, and freeze-dried to obtain a terminal olefin hyperbranched polymer.

[0038] (3) 1 kg of polypropylene dried at 80°C in a blast drying oven for 2 hours, 80 g of terminal olefin hyperbranched polymer, 3 g of benzoyl peroxide and 1 g of antioxidant (antioxidant 1010 and antioxidant 168 compounded in a weight ratio of 1:1) were added to a high-speed mixer and mixed at 2000 rpm for 10 minutes. The mixture was then added to a twin-screw extruder. The parameters of the twin-screw extruder were as follows: feeding section temperature: 160°C, compression section temperature: 180°C, homogenization section temperature: 200°C, die head temperature: 200°C, and screw speed of 200 rpm. The material was extruded, granulated, cooled, washed with acetone, and dried to obtain a grafted modified PP material.

[0039] Example 2: A specific preparation method of a graft-modified PP material, comprising the following steps:

[0040] (1) 80 g of diglycidyl terephthalate, 96 g of ethanolamine phosphate, and 0.16 g of triethylamine were added to 800 g of DMAC, heated to 70° C. with stirring, reacted for 14 h, cooled to room temperature, and then 10% dilute hydrochloric acid was added to adjust the pH to neutral. 1.6 kg of 5° C. acetone was then added. The resulting precipitate was centrifuged and recrystallized from tetrahydrofuran / ether to obtain a hyperbranched polymer.

[0041] (2) 150 g of the hyperbranched polymer obtained in (1), 105 g of glycidyl methacrylate, and 3 g of triethylamine were added to 1.5 kg of DMAC, and the mixture was heated to 90° C. with stirring, reacted for 7 h, cooled to room temperature, and then 10% dilute hydrochloric acid was added to adjust the pH to neutral. 3 kg of n-hexane was then added, and the resulting precipitate was centrifuged, washed with petroleum ether, washed with deionized water, and freeze-dried to obtain a terminal olefin hyperbranched polymer;

[0042] (3) 1 kg of polypropylene dried at 85°C in a blast drying oven for 3 hours, 120 g of terminal olefin hyperbranched polymer, 5 g of benzoyl peroxide and 3 g of antioxidant (antioxidant 1010 and antioxidant 168 compounded in a weight ratio of 1:1) were added to a high-speed mixer and mixed at 2500 rpm for 12 minutes. The mixture was then added to a twin-screw extruder. The parameters of the twin-screw extruder were as follows: feeding section temperature: 165°C, compression section temperature: 190°C, homogenization section temperature: 210°C, die head temperature: 210°C, and screw speed of 250 rpm. The material was extruded, granulated, cooled, washed with acetone, and dried to obtain a grafted modified PP material.

[0043] Example 3: A specific preparation method of a graft-modified PP material, comprising the following steps:

[0044] (1) 60 g of diglycidyl terephthalate, 84 g of ethanolamine phosphate, and 0.18 g of triethylamine were added to 720 g of DMAC, heated to 100° C. with stirring, reacted for 16 h, cooled to room temperature, and then 10% dilute hydrochloric acid was added to adjust the pH to neutral. 1.44 kg of 5° C. acetone was then added. The resulting precipitate was centrifuged and recrystallized from tetrahydrofuran / ether to obtain a hyperbranched polymer.

[0045] (2) 120 g of the hyperbranched polymer obtained in (1), 96 g of glycidyl methacrylate, and 1.2 g of triethylamine were added to 1.44 kg of DMAC, and the mixture was heated to 80° C. with stirring, and reacted for 8 h. After cooling to room temperature, 10% dilute hydrochloric acid was added to adjust the pH to neutral, and 2.88 kg of n-hexane was added. The resulting precipitate was centrifuged, washed with petroleum ether, washed with deionized water, and freeze-dried to obtain a terminal olefin hyperbranched polymer;

[0046] (3) 1 kg of polypropylene dried at 90°C in a blast drying oven for 4 hours, 150 g of terminal olefin hyperbranched polymer, 7 g of benzoyl peroxide and 5 g of antioxidant (antioxidant 1010 and antioxidant 168 compounded in a weight ratio of 1:1) were added to a high-speed mixer and mixed at 3000 rpm for 15 minutes. The mixture was then added to a twin-screw extruder. The parameters of the twin-screw extruder were as follows: feeding section temperature: 170°C, compression section temperature: 200°C, homogenization section temperature: 220°C, die head temperature: 220°C, and screw speed of 300 rpm. The material was extruded, granulated, cooled, washed with acetone, and dried to obtain a grafted modified PP material.

[0047] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that the weight ratio of polypropylene to terminal olefin hyperbranched polymer is 100:20. The specific preparation process is as follows: A specific preparation method of a graft-modified PP material comprises the following steps:

[0048] (1) 120 g of diglycidyl terephthalate, 168 g of ethanolamine phosphate, and 0.36 g of triethylamine were added to 1.44 kg of DMAC, heated to 100° C. with stirring, reacted for 16 h, cooled to room temperature, and then 10% dilute hydrochloric acid was added to adjust the pH to neutral. 2.88 kg of 5° C. acetone was then added. The resulting precipitate was centrifuged and recrystallized from tetrahydrofuran / ether to obtain a hyperbranched polymer.

[0049] (2) 180 g of the hyperbranched polymer obtained in (1), 144 g of glycidyl methacrylate, and 1.8 g of triethylamine were added to 2.16 kg of DMAC, and the mixture was heated to 80° C. with stirring, and reacted for 8 h. After cooling to room temperature, 10% dilute hydrochloric acid was added to adjust the pH to neutral, and 4.32 kg of n-hexane was added. The resulting precipitate was centrifuged, washed with petroleum ether, washed with deionized water, and freeze-dried to obtain a terminal olefin hyperbranched polymer;

[0050] (3) 1 kg of polypropylene dried at 90°C in a forced air drying oven for 4 hours, 200 g of terminal olefin hyperbranched polymer, 7 g of benzoyl peroxide and 5 g of antioxidant (antioxidant 1010 and antioxidant 168 compounded in a weight ratio of 1:1) were added to a high-speed mixer and mixed at 3000 rpm for 15 minutes. The mixture was then added to a twin-screw extruder. The parameters of the twin-screw extruder were as follows: feeding section temperature: 170°C, compression section temperature: 200°C, homogenization section temperature: 220°C, die head temperature: 220°C, and screw speed of 300 rpm. The material was extruded, granulated, cooled, washed with acetone, and dried to obtain a grafted modified PP material.

[0051] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that the weight ratio of polypropylene to carboxyl-terminated hyperbranched polymer is 100:25. The specific preparation process is as follows: A specific preparation method of a graft-modified PP material comprises the following steps:

[0052] (1) 120 g of diglycidyl terephthalate, 168 g of ethanolamine phosphate, and 0.36 g of triethylamine were added to 1.44 kg of DMAC, heated to 100° C. with stirring, reacted for 16 h, cooled to room temperature, and then 10% dilute hydrochloric acid was added to adjust the pH to neutral. 2.88 kg of 5° C. acetone was then added. The resulting precipitate was centrifuged and recrystallized from tetrahydrofuran / ether to obtain a hyperbranched polymer.

[0053] (2) 180 g of the hyperbranched polymer obtained in (1), 144 g of glycidyl methacrylate, and 1.8 g of triethylamine were added to 2.16 kg of DMAC, and the mixture was heated to 80° C. with stirring, and reacted for 8 h. After cooling to room temperature, 10% dilute hydrochloric acid was added to adjust the pH to neutral, and 4.32 kg of n-hexane was added. The resulting precipitate was centrifuged, washed with petroleum ether, washed with deionized water, and freeze-dried to obtain a terminal olefin hyperbranched polymer;

[0054] (3) 1 kg of polypropylene dried at 90°C in a blast drying oven for 4 hours, 250 g of terminal olefin hyperbranched polymer, 7 g of benzoyl peroxide and 5 g of antioxidant (antioxidant 1010 and antioxidant 168 compounded in a weight ratio of 1:1) were added to a high-speed mixer and mixed at 3000 rpm for 15 minutes. The mixture was then added to a twin-screw extruder. The parameters of the twin-screw extruder were as follows: feeding section temperature: 170°C, compression section temperature: 200°C, homogenization section temperature: 220°C, die head temperature: 220°C, and screw speed of 300 rpm. The material was extruded, granulated, cooled, washed with acetone, and dried to obtain a grafted modified PP material.

[0055] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that the hyperbranched polymer is not end-capped with glycidyl methacrylate. The specific preparation process is as follows: A specific preparation method of a graft-modified PP material includes the following steps:

[0056] (1) 60 g of diglycidyl terephthalate, 84 g of ethanolamine phosphate, and 0.18 g of triethylamine were added to 720 g of DMAC, heated to 100° C. with stirring, reacted for 16 h, cooled to room temperature, and then 10% dilute hydrochloric acid was added to adjust the pH to neutral. 1.44 kg of 5° C. acetone was then added. The resulting precipitate was centrifuged and recrystallized from tetrahydrofuran / ether to obtain a hyperbranched polymer.

[0057] (2) 1 kg of polypropylene dried at 90°C in a blast drying oven for 4 hours, 150 g of the hyperbranched polymer obtained in (1) and 5 g of an antioxidant (antioxidant 1010 and antioxidant 168 compounded in a weight ratio of 1:1) were added to a high-speed mixer and mixed at 3000 rpm for 15 minutes. The mixture was then added to a twin-screw extruder. The parameters of the twin-screw extruder were as follows: feeding section temperature: 170°C, compression section temperature: 200°C, homogenization section temperature: 220°C, die head temperature: 220°C, and screw speed of 300 rpm. The material was extruded, granulated, cooled, washed with acetone, and dried to obtain a grafted modified PP material.

[0058] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that the hyperbranched polymer does not contain P and N elements. The specific preparation process is as follows: A specific preparation method of a graft-modified PP material includes the following steps:

[0059] (1) 60 g of diglycidyl terephthalate, 84 g of 1,3-dihydroxyacetone, and 0.6 g of triethylamine were added to 720 g of DMAC, heated to 100° C. with stirring, reacted for 16 h, cooled to room temperature, and then 10% dilute hydrochloric acid was added to adjust the pH to neutral. 1.44 kg of 5° C. acetone was then added. The resulting precipitate was centrifuged and recrystallized from tetrahydrofuran / ether to obtain a hyperbranched polymer.

[0060] (2) 120 g of the hyperbranched polymer obtained in (1), 96 g of glycidyl methacrylate, and 1.2 g of triethylamine were added to 1.44 kg of DMAC, and the mixture was heated to 80° C. with stirring, and reacted for 8 h. After cooling to room temperature, 10% dilute hydrochloric acid was added to adjust the pH to neutral, and 2.88 kg of n-hexane was added. The resulting precipitate was centrifuged, washed with petroleum ether, washed with deionized water, and freeze-dried to obtain a terminal olefin hyperbranched polymer;

[0061] (3) 1 kg of polypropylene dried at 90°C in a blast drying oven for 4 hours, 150 g of terminal olefin hyperbranched polymer, 7 g of benzoyl peroxide and 5 g of antioxidant (antioxidant 1010 and antioxidant 168 compounded in a weight ratio of 1:1) were added to a high-speed mixer and mixed at 3000 rpm for 15 minutes. The mixture was then added to a twin-screw extruder. The parameters of the twin-screw extruder were as follows: feeding section temperature: 170°C, compression section temperature: 200°C, homogenization section temperature: 220°C, die head temperature: 220°C, and screw speed of 300 rpm. The material was extruded, granulated, cooled, washed with acetone, and dried to obtain a grafted modified PP material.

[0062] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that diglycidyl terephthalate is replaced with bis(2,3-epoxypropyl) malonate. The specific preparation process is as follows: A specific preparation method of a graft-modified PP material includes the following process:

[0063] (1) 60 g of bis(2,3-epoxypropyl) malonate, 84 g of ethanolamine phosphate, and 0.18 g of triethylamine were added to 720 g of DMAC, heated to 100° C. with stirring, reacted for 16 h, cooled to room temperature, and then 10% dilute hydrochloric acid was added to adjust the pH to neutral. 1.44 kg of 5° C. acetone was then added, and the resulting precipitate was centrifuged and recrystallized from tetrahydrofuran / ether to obtain a hyperbranched polymer;

[0064] (2) 120 g of the hyperbranched polymer obtained in (1), 96 g of glycidyl methacrylate, and 1.2 g of triethylamine were added to 1.44 kg of DMAC, and the mixture was heated to 80° C. with stirring, and reacted for 8 h. After cooling to room temperature, 10% dilute hydrochloric acid was added to adjust the pH to neutral, and 2.88 kg of n-hexane was added. The resulting precipitate was centrifuged, washed with petroleum ether, washed with deionized water, and freeze-dried to obtain a terminal olefin hyperbranched polymer;

[0065] (3) 1 kg of polypropylene dried at 90°C in a blast drying oven for 4 hours, 150 g of terminal olefin hyperbranched polymer, 7 g of benzoyl peroxide and 5 g of antioxidant (antioxidant 1010 and antioxidant 168 compounded in a weight ratio of 1:1) were added to a high-speed mixer and mixed at 3000 rpm for 15 minutes. The mixture was then added to a twin-screw extruder. The parameters of the twin-screw extruder were as follows: feeding section temperature: 170°C, compression section temperature: 200°C, homogenization section temperature: 220°C, die head temperature: 220°C, and screw speed of 300 rpm. The material was extruded, granulated, cooled, washed with acetone, and dried to obtain a grafted modified PP material.

[0066] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that diglycidyl terephthalate is replaced by terephthalic acid. The specific preparation process is as follows: A specific preparation method of a graft-modified PP material includes the following process:

[0067] (1) Under nitrogen protection, 60 g of terephthalic acid, 84 g of ethanolamine phosphate, and 0.18 g of p-toluenesulfonic acid were added to 720 g of xylene, and the mixture was heated to 160° C. with stirring, and reacted for 8 h. After cooling to room temperature, a saturated sodium bicarbonate solution was added to adjust the pH to neutral, and the solvent and water were removed by distillation under reduced pressure. The crude product was added to 720 g of tetrahydrofuran, and then 1.44 kg of 5° C. diethyl ether was added. The resulting precipitate was filtered, washed, and dried to obtain a linear polymer.

[0068] (2) 120 g of the linear polymer obtained in (1), 96 g of glycidyl methacrylate, and 1.2 g of triethylamine were added to 1.44 kg of DMAC, and the mixture was heated to 80° C. with stirring, and reacted for 8 h. After cooling to room temperature, 10% dilute hydrochloric acid was added to adjust the pH to neutral, and 2.88 kg of n-hexane was added. The resulting precipitate was centrifuged, washed with petroleum ether, washed with deionized water, and freeze-dried to obtain an olefin-terminated linear polymer.

[0069] (3) 1 kg of polypropylene dried at 90°C in a forced air drying oven for 4 hours, 150 g of terminal olefin-based linear polymer, 7 g of benzoyl peroxide and 5 g of antioxidant (antioxidant 1010 and antioxidant 168 were compounded in a weight ratio of 1:1) were added to a high-speed mixer and mixed at 3000 rpm for 15 minutes. The mixture was then added to a twin-screw extruder. The parameters of the twin-screw extruder were as follows: feeding section temperature: 170°C, compression section temperature: 200°C, homogenization section temperature: 220°C, die head temperature: 220°C, and screw speed of 300 rpm. The material was extruded, granulated, cooled, washed with acetone, and dried to obtain a grafted modified PP material.

[0070] Blank comparative example: The difference between the blank comparative example and Example 3 is that polypropylene purchased from Shanghai MacLean Biochemical Technology Co., Ltd. is directly used, and the melt index is 5-12 g / 10 min.

[0071] Performance testing:

[0072] 1. Mechanical Property Test: The PP materials prepared in Examples 1-3, Comparative Examples 1-6, and a blank comparative example were prepared into experimental specimens of uniform size. Tensile strength tests, elongation at break tests, and cantilever beam notched impact tests were performed at 23°C and -30°C using a universal material testing machine at a tensile rate of 50 mm / min. The experimental results are shown in Table 1.

[0073] 2. Flame retardant performance test: The PP materials prepared in Examples 1-3, Comparative Examples 1-6, and a blank comparative example were prepared into experimental specimens of uniform size and subjected to vertical burning test and limiting oxygen index test. The experimental results are shown in Table 2.

[0074] Table 1 Mechanical properties

[0075]

[0076] Table 2 Flame retardant properties

[0077]

[0078]

[0079] Data Analysis:

[0080] It can be seen from the experimental data in Table 1 and Table 2 that the grafted modified PP material prepared by Examples 1-3 using the present invention has good mechanical properties at room temperature and a high performance retention rate in a low-temperature environment, and also performs well in flame retardant properties. Among them, Example 3 has the best comprehensive performance and the highest performance retention rate in a low-temperature environment. It has good flame retardant properties while having excellent low-temperature mechanical properties.

[0081] From the experimental data in Table 1 and Table 2, it can be seen that with the increase in the addition amount of terminal olefin hyperbranched polymer, the various properties of the materials in Examples 1-3 and Comparative Examples 1-2 first increase and then decrease. This may be because as the proportion of hyperbranched structure in the PP material modified by the terminal olefin hyperbranched polymer increases, the crystallinity of the material is reduced, thereby reducing the tensile strength of the material. The softer molecular chain improves the elongation at break and the notched impact strength of the material. When facing a low temperature environment, the introduction of the hyperbranched structure causes the Tg of the material to shift to a low temperature, ensuring the mobility of the molecular chain segments of the material in a low temperature environment, and the performance retention rate of the material in a low temperature environment is improved. At the same time, with the increase of the P and N element content, the flame retardant properties of the material are also improved. However, with the further increase of the hyperbranched structure content, the crosslinking density of this grafted modified PP material is too high, which restricts the movement of the molecular chain and the rigidity of the material is too strong, which leads to a decrease in the mechanical properties of the material. When facing a low temperature environment, the excessively high hyperbranched structure leads to agglomeration, deterioration of the interface compatibility, and easy brittle fracture at low temperatures, thereby reducing the low temperature performance retention rate of the material.

[0082] It can be seen from the experimental data in Tables 1 and 2 that in Comparative Example 3, the hyperbranched polymer is added by blending, and the performance of the material is not as good as that of Example 3 using the grafting method. This may be because blending as a physical mixing method is far less dispersible than grafting, which is a chemical mixing method, resulting in insufficient cross-linking of the material and a lower crystallinity decrease rate than Example 3. The material has strong rigidity and weak toughness, and at room temperature, it exhibits high tensile strength but low elongation at break and notched impact strength. When facing a low-temperature environment, the Tg does not shift toward low temperatures as much as in Example 3, and the material's low-temperature mechanical property retention rate is insufficient.

[0083] As can be seen from the experimental data in Tables 1 and 2, the mechanical properties of the material in Comparative Example 4 are roughly the same as those of Example 3, but the flame retardant properties are significantly different. This may be because the hyperbranched polymer added to Comparative Example 4 does not contain the key P and N flame retardant elements and cannot achieve a flame retardant effect through gas-phase flame retardancy and condensed-phase carbon layer formation. In contrast, the P and N in Example 3 synergistically form a dense carbon layer during combustion and inhibit dripping. At the same time, although the hyperbranched polymer in Comparative Example 4, which does not contain polar groups, has slightly poor compatibility with polypropylene, the branched structure still retains a certain toughening effect, resulting in no significant attenuation of the mechanical properties.

[0084] It can be seen from the experimental data in Table 1 and Table 2 that the reason for the decline in material performance in Comparative Example 5 may be that the hyperbranched polymer added in Comparative Example 5 lacks a benzene ring structure. The lack of the steric hindrance effect brought by the benzene ring increases the crystallinity of the material, resulting in an increase in the tensile strength of the material, and a decrease in the elongation at break and the notched impact strength. When facing a low temperature environment, the higher crystallinity gives the material a higher Tg, resulting in the low-temperature performance of the material being inferior to that of Example 3. In terms of flame retardant performance, the rigid skeleton of the benzene ring forms a stable carbon layer support network during combustion, ensuring that the P and N elements are evenly distributed and continue to play a role. However, in Comparative Example 5, due to the lack of benzene ring support, the molecular chain easily collapses at high temperatures, the carbon layer is loose, and the P and N elements escape with the decomposition products, resulting in dripping and a decrease in flame retardant efficiency.

[0085] It can be seen from the experimental data in Table 1 and Table 2 that, except for the tensile strength, the performance of Comparative Example 6 is significantly different from that of Example 3 in other properties. This may be because the terminal olefin hyperbranched polymer of Example 3 optimizes the polypropylene molecular chain through the branched three-dimensional network structure, inhibits crystallization and enhances the flexibility of the amorphous region, thereby improving its elongation at break and notched impact strength; while the linear polymer of Comparative Example 6 lacks a branched structure and cannot form an interpenetrating network, resulting in excessive material rigidity and weak interfacial bonding. The branching points of the hyperbranched structure form physical entanglements with PP through the rigid benzene ring skeleton, significantly improving the toughness of the material, while the linear structure is more susceptible to brittle fracture at low temperatures due to the easy slippage of the molecular chain segments.

[0086] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A graft modified PP material, characterized in that: The invention comprises the following raw materials in parts by weight: polypropylene: 100 parts, terminal olefin hyperbranched polymer: 8-15 parts, initiator: 0.3-0.7 parts, antioxidant: 0.1-0.5 parts. The preparation process of the terminal olefin hyperbranched polymer is as follows: (1) Preparation of hyperbranched polymer: Diglycidyl terephthalate, ethanolamine phosphate, and triethylamine were added to N,N-dimethylacetamide (DMAC), heated to 60-80°C with stirring, reacted for 12-16 hours, cooled to room temperature, and then diluted hydrochloric acid was added to adjust the pH to neutral. Then, 5°C acetone was added, and the resulting precipitate was centrifuged and recrystallized from tetrahydrofuran / ether to obtain a hyperbranched polymer. (2) Preparation of terminal olefin hyperbranched polymer: The hyperbranched polymer obtained in (1), glycidyl methacrylate, and triethylamine were added to DMAC, heated to 80-100° C. with stirring, reacted for 6-8 hours, cooled to room temperature, and then diluted hydrochloric acid was added to adjust the pH to neutral. Then, n-hexane was added, and the obtained precipitate was centrifuged, washed with petroleum ether, washed with deionized water, and freeze-dried to obtain a terminal olefin hyperbranched polymer.

2. The graft-modified PP material according to claim 1, characterized in that: The melt index of the polypropylene is 5-12 g / 10 min.

3. The graft-modified PP material according to claim 1, characterized in that: The initiator is benzoyl peroxide.

4. The graft-modified PP material according to claim 1, characterized in that: The antioxidant refers to antioxidant 1010 and antioxidant 168 compounded in a weight ratio of 1:

1.

5. The graft-modified PP material according to claim 1, characterized in that: In the (1), the weight ratio of diglycidyl terephthalate, ethanolamine phosphate, triethylamine, DMAC and 5° C. acetone is 1:1.2-1.4:0.001-0.003:8-12:16-24, and the dilute hydrochloric acid refers to a hydrochloric acid solution with a concentration of 10%.

6. The graft-modified PP material according to claim 1, characterized in that: In the (2), the weight ratio of the hyperbranched polymer, glycidyl methacrylate, triethylamine, DMAC and n-hexane is 1:0.6-0.8:0.01-0.03:8-12:16-24, and the dilute hydrochloric acid refers to a hydrochloric acid solution with a concentration of 10%.

7. The method for preparing the graft-modified PP material according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: adding polypropylene, terminal olefin hyperbranched polymer, initiator and antioxidant into a high-speed mixer, mixing at 2000-3000 rpm for 10-15 minutes, then adding the mixture into a twin-screw extruder, extruding, granulating, cooling, washing with acetone and drying to obtain a graft-modified PP material.

8. The method for preparing the graft-modified PP material according to claim 7, characterized in that: The polypropylene is first placed in a forced air drying oven and maintained at 80-90° C. for 2-4 hours.

9. The method for preparing the graft-modified PP material according to claim 7, characterized in that: The parameters of the twin-screw extruder are as follows: feeding section temperature: 160-170°C, compression section temperature: 180-200°C, homogenization section temperature: 200-220°C, die head temperature: 200-220°C, and screw speed 200-300rpm.

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