A method for preparing a high-toughness polylactic acid random copolymer polypropylene blend material

Abstract

A method for preparing a high-toughness polylactic acid (PLA) random copolymer polypropylene blend is disclosed. The method involves melt-blending random copolymer polypropylene and a polypropylene-based elastomer in a twin-screw extruder at a specific ratio to obtain a modified random copolymer polypropylene blend. Then, an initiator, grafting monomer, and co-grafting monomer are uniformly mixed and added to the blend, followed by solvent-free grafting via melt blending to obtain a high-graft-rate random copolymer polypropylene graft copolymer. Finally, the high-graft-rate random copolymer polypropylene graft copolymer, random copolymer polypropylene, polylactic acid, and a compatibilizer are melt-blended to obtain a high-toughness PLA / random copolymer polypropylene blend. This PLA / random copolymer polypropylene blend exhibits high toughness and good compatibility, significantly expanding the application range of PLA and showing broad application prospects.

Description

Technical Field

[0001] This invention relates to a method for preparing polypropylene blends, and more particularly to a method for preparing high-toughness polylactic acid random copolymer polypropylene blends. Background Technology

[0002] Polylactic acid (PLA) is a linear polyester polymerized from lactic acid and is a fully biodegradable material. Compared to traditional plastics, PLA has excellent biodegradability. PLA itself is non-toxic and harmless, and its raw materials are all derived from renewable resources, such as agricultural products. PLA is widely used in medical, packaging, and other fields and has broad research and application prospects. However, its poor toughness limits its further promotion and application.

[0003] Compared to traditional rubber, thermoplastic elastomers exhibit rubber-like elasticity at room temperature and can be plasticized at high temperatures, allowing for repeated processing and reuse through extrusion and injection molding. Because thermoplastic elastomers possess a certain degree of crystallinity, they can achieve sufficient strength without cross-linking. Propylene-based elastomers are generally random copolymers of propylene and ethylene, possessing advantages such as low density, good chemical resistance, and safety and non-toxicity, making them suitable as toughening materials for polylactic acid (PLA). However, direct use is too costly; therefore, they are blended with random copolymer polypropylene, and then further blended with PLA. However, since PLA and random copolymer polypropylene are incompatible systems, improving the compatibility of the blends is essential.

[0004] The invention patent with publication number CN 106554607 A discloses a method for preparing a high-toughness polyolefin / polylactic acid-based alloy material. The method improves the toughness of the polylactic acid blend by blending polylactic acid with a polyolefin elastomer. Although the toughness of the blend is improved, the increase is not significant.

[0005] Patent CN 103131150 A discloses a polypropylene / polylactic acid / starch composite material and its preparation method. By combining polypropylene, polylactic acid, diisocyanate-modified starch, vegetable oil polyol, and a compatibilizer, a polypropylene / polylactic acid / starch composite material with good interfacial compatibility is prepared. However, the starch modification process is relatively complex and time-consuming, resulting in a low elongation at break of the final blend. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a high-toughness polylactic acid random copolymer polypropylene blend. This invention involves melt blending a polypropylene-based elastomer with random copolymer polypropylene, followed by the addition of grafting monomers and co-grafting monomers to conduct an in-situ grafting reaction during melt blending, resulting in a high-grafting-rate random copolymer polypropylene graft copolymer. The blend prepared by this invention exhibits high toughness, good compatibility, low cost, and is safe and non-toxic, possessing broad application prospects. The prepared polylactic acid / random copolymer polypropylene blend also demonstrates good toughness and processing performance.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a high-toughness polylactic acid random copolymer polypropylene blend, wherein the preparation process of the high-graft-rate random copolymer polypropylene graft copolymer involves first blending the random copolymer polypropylene with a polypropylene-based elastomer, and then performing a grafting treatment; the method includes the following preparation steps:

[0009] (1) Random copolymer polypropylene is melt-blended with polypropylene-based elastomer, and then grafting monomer, co-grafting monomer and initiator are added for melt blending to prepare random copolymer polypropylene graft copolymer with high grafting rate.

[0010] (2) Preparation of blended materials: Before melt processing, the sample needs to be placed in a vacuum oven and dried under the required conditions; polylactic acid, random copolymer polypropylene, high grafting rate random copolymer polypropylene graft copolymer obtained in step (1), compatibilizer, and initiator are mixed uniformly in the required proportion and then melt-blended in a twin-screw extruder to prepare a polylactic acid / random copolymer polypropylene blended material with high toughness;

[0011] The mass ratio of random copolymer polypropylene to polypropylene-based elastomer is 9:1-5:5, with 1-5 parts of graft monomer, 2-10 parts of co-graft monomer, and 0.1-0.5 parts of initiator; the blending materials are 50-90 parts of polylactic acid, 0-50 parts of random copolymer polypropylene, and 10-50 parts of high-graft-rate random copolymer polypropylene graft copolymer, with 1-15 parts of compatibilizer and 0.1-0.5 parts of initiator added.

[0012] The method for preparing a high-toughness polylactic acid random copolymer polypropylene blend material, wherein the melt index of the polypropylene-based elastomer is 2-4 g / 10 min (190℃, 2.16 kg), the polyethylene content is 5-25%, and the polypropylene content is 75-95%.

[0013] The method for preparing a high-toughness polylactic acid random copolymer polypropylene blend material, wherein the grafting monomer is at least one of glycidyl methacrylate, maleic anhydride, methyl methacrylate, butyl acrylate, and vinyl alcohol; the grafting agent is one or more of styrene, α-methylstyrene, acrylic acid, and dimethylformamide; and the initiator is one or more of azobisisobutyronitrile, dicumyl peroxide, cumyl hydroperoxide, and benzoyl peroxide.

[0014] The method for preparing a high-toughness polylactic acid random copolymer polypropylene blend material, wherein the compatibilizer is at least one of iconic acid, dibutyl iconic acid, succinic acid, salicylic acid, and citric acid, and the initiator used is one or more of azobisisobutyronitrile, dicumyl peroxide, cumyl hydroperoxide, and benzoyl peroxide.

[0015] The advantages and effects of this invention are:

[0016] 1. This invention proposes and implements a high-toughness polylactic acid / random copolymer polypropylene blend material and its preparation method. Compared with traditional methods for toughening polylactic acid, the toughness of the blend can be significantly improved. This is because the random copolymer polypropylene is blended with a polypropylene-based elastomer and then subjected to a solvent-free grafting reaction with grafting monomers. This significantly increases the grafting rate, resulting in a higher content of active groups in the blend and a greater probability of inter-group reaction when blended with polylactic acid. Furthermore, a reactive compatibilizer is simultaneously added to the blend system for synergistic compatibilization, which greatly promotes the chemical reaction between polypropylene and polylactic acid, thereby improving the interfacial strength between the two phases.

[0017] 2. In this invention, the material blended with polylactic acid is a blend of random copolymer polypropylene and polypropylene-based elastomer, rather than using elastomer to toughen polylactic acid entirely, which is less costly; the elastomer used is safe and non-toxic, and the resulting high-toughness polylactic acid / random copolymer polypropylene blend is also safe and non-toxic.

[0018] 3. The processing equipment required for this invention is simple; a high-toughness polylactic acid / random copolymer polypropylene blend can be produced simply through mechanical blending. Furthermore, compared to toughening with a single type of elastomer, this invention achieves superior results with less elastomer through synergistic toughening, undoubtedly giving this material significant market competitiveness and generating substantial profits for enterprises.

[0019] 4. This invention uses a polypropylene-based elastomer to melt-blend random copolymer polypropylene, followed by the addition of grafting monomers and co-grafting monomers for in-situ grafting reaction, resulting in a high-graft-rate random copolymer polypropylene graft copolymer. The obtained high-graft-rate random copolymer polypropylene graft copolymer is then melt-blended with polylactic acid and a compatibilizer to finally obtain a high-toughness polylactic acid / random copolymer polypropylene blend material. The polypropylene-based elastomer used in this invention is completely compatible with the random copolymer polypropylene. The method of blending before grafting avoids reactions between functional groups, thereby increasing the content of reactive groups. The addition of co-grafting monomers improves grafting efficiency, further increasing the content of reactive groups in the random copolymer polypropylene. The synergistic effect of the high-graft-rate random copolymer polypropylene graft copolymer and the compatibilizer greatly improves the compatibility between the random copolymer polypropylene and polylactic acid. The polylactic acid / random copolymer polypropylene blends prepared by this method can significantly improve toughness compared with blends containing a single compatibilizer or ordinary grafts, and the cost is significantly lower than that of directly blending polypropylene-based elastomers with polylactic acid. Implementation

[0020] The present invention will now be described in detail through specific embodiments. It should be noted that these embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-substantial improvements and adjustments to the present invention based on the above-described content.

[0021] Source of raw materials

[0022] Polylactic acid, 4032D, Natureworks; Random copolymer polypropylene, NS06, Wuhan Sinopec; Random copolymer polypropylene, Hifax CA10A, Basel, Germany; Polypropylene-based elastomer, Versify 2300, Dow Chemical Company; Polypropylene-based elastomer, Vistamaxx 6102, ExxonMobil; Maleic anhydride, chemically pure, Beijing Chemical Plant; Glycidyl methacrylate, chemically pure, Suzhou Anli Chemical Plant; Styrene, polymerization grade, Jilin Petrochemical Company of China National Petroleum Corporation; Alpha-methylstyrene, chemically pure, Sinopharm Chemical Reagent Co., Ltd.; Azobisisobutyronitrile, chemically pure, Shandong Jinghao Chemical Co., Ltd.; Dicumyl peroxide, chemically pure, Chengdu Best Reagent Co., Ltd.; Cumyl peroxide, industrial grade, Wuhan Adama New Energy Co., Ltd.; Dibutyl etherate, industrial grade, Hubei Xinghengye Co., Ltd.; Citric acid, industrial grade, Shenyang Jintai Chemical Co., Ltd.

[0023] Comparative Example 1

[0024] 100 parts of polylactic acid

[0025] Polylactic acid (PLA) was injection molded into tensile and impact specimens using a miniature injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard using an impact hammer with an energy of 2.75 J at a test temperature of 23℃.

[0026] Comparative Example 2

[0027] 80 parts of polylactic acid

[0028] 20 parts of random copolymer polypropylene (NS06)

[0029] Polylactic acid and random copolymerized polypropylene graft copolymer were uniformly mixed and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder was set to 180-200℃ and the screw speed was 200-250 r / min. The extruded strips were cooled with water and then granulated for later use.

[0030] Polylactic acid / random copolymer polypropylene blends were injection molded into tensile and impact specimens using a miniature injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard using an impact hammer with an energy of 2.75 J at a test temperature of 23℃.

[0031] Comparative Example 3

[0032] 50 parts of polylactic acid

[0033] 50 parts of random copolymer polypropylene (NS06)

[0034] Polylactic acid and random copolymerized polypropylene graft copolymer were uniformly mixed and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder was set to 180-200℃ and the screw speed was 200-250 r / min. The extruded strips were cooled with water and then granulated for later use.

[0035] Polylactic acid / random copolymer polypropylene blends were injection molded into tensile and impact specimens using a miniature injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard using an impact hammer with an energy of 2.75 J at a test temperature of 23℃.

[0036] Comparative Example 4

[0037] 50 parts of polylactic acid

[0038] 40 parts of random copolymer polypropylene (Hifax CA10A)

[0039] 10 parts of polypropylene-based elastomer (Versify 2300)

[0040] Polylactic acid, random copolymer polypropylene and polypropylene-based elastomer are uniformly mixed and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded strips are cooled with water and then granulated for later use.

[0041] Polylactic acid / random copolymer polypropylene blends were injection molded into tensile and impact specimens using a miniature injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard using an impact hammer with an energy of 2.75 J at a test temperature of 23℃.

[0042] Comparative Example 5

[0043] 60 parts of polylactic acid

[0044] 31 parts of random copolymer polypropylene (Hifax CA10A)

[0045] 9 parts of polypropylene-based elastomer (Versify 2300)

[0046] (1) Random copolymer polypropylene and polypropylene-based elastomer are uniformly mixed at a mass ratio of 7:3 and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then granulated to obtain a random copolymer polypropylene / polypropylene-based elastomer blend for later use.

[0047] (2) After uniformly mixing polylactic acid, random copolymer polypropylene and the random copolymer polypropylene / polypropylene-based elastomer blend obtained in step (1), melt blend in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded strip is cooled with water and then granulated for later use.

[0048] The polylactic acid / random copolymer polypropylene blend obtained in step (2) was injection molded into tensile and impact test specimens using a micro injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard using an impact hammer with an energy of 2.75 J and a test temperature of 23℃.

[0049] Comparative Example 6

[0050] 50 parts of polylactic acid

[0051] 38 parts of random copolymer polypropylene (Hifax CA10A)

[0052] 12 parts of polypropylene-based elastomer (Vistamaxx 6102)

[0053] 5 parts of dibutyl ioconate

[0054] 0.2 parts of azobisisobutyronitrile

[0055] (1) Random copolymer polypropylene and polypropylene-based elastomer are uniformly mixed at a mass ratio of 7:3 and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then granulated to obtain a random copolymer polypropylene / polypropylene-based elastomer blend for later use.

[0056] (2) Polylactic acid, random copolymer polypropylene, random copolymer polypropylene / polypropylene-based elastomer blend obtained in step (1), dibutyl etherate, and azobisisobutyronitrile are uniformly mixed and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded strips are cooled with water and then granulated for later use.

[0057] The polylactic acid / random copolymer polypropylene blend obtained in step (2) was injection molded into tensile specimens and impact specimens using a micro injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard, using an impact hammer with an energy of 2.75 J and a test temperature of 23℃.

[0058] Comparative Example 7

[0059] 60 parts of polylactic acid

[0060] 28 parts of random copolymer polypropylene (Hifax CA10A)

[0061] 12 parts of polypropylene-based elastomer (Vistamaxx 6102)

[0062] 2 parts maleic anhydride

[0063] 4 parts of α-methylstyrene

[0064] 0.2 parts of dicumyl peroxide

[0065] (1) Random copolymer polypropylene and polypropylene-based elastomer are uniformly mixed at a mass ratio of 7:3 and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then granulated to obtain a random copolymer polypropylene / polypropylene-based elastomer blend for later use.

[0066] (2) The blend obtained in step (1) is uniformly mixed with maleic anhydride, α-methylstyrene and dicumyl peroxide and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then granulated to obtain a high grafting rate random copolymer polypropylene graft copolymer for later use.

[0067] (3) Polylactic acid, high grafting rate random copolymer polypropylene graft copolymer obtained in step (2) and dicumyl peroxide are uniformly mixed and melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded strip is cooled with water and then granulated for later use.

[0068] The polylactic acid / random copolymer polypropylene blend obtained in step (3) was injection molded into tensile specimens and impact specimens using a micro injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard, using an impact hammer with an energy of 2.75 J and a test temperature of 23℃. Example 1

[0069] 50 parts of polylactic acid

[0070] 25 parts of random copolymer polypropylene (NS06)

[0071] 25 parts of polypropylene-based elastomer (Versify 2300)

[0072] 2 parts maleic anhydride

[0073] 4 parts of α-methylstyrene

[0074] 5 parts of dibutyl ioconate

[0075] 0.2 parts of azobisisobutyronitrile

[0076] (1) Random copolymer polypropylene and polypropylene-based elastomer are uniformly mixed at a mass ratio of 5:5 and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then pelletized to obtain a random copolymer polypropylene / polypropylene-based elastomer blend for later use.

[0077] (2) The blend obtained in step (1) is uniformly mixed with maleic anhydride, α-methylstyrene and azobisisobutyronitrile and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. After the extruded sample is cooled with water, it is granulated to obtain a high grafting rate random copolymer polypropylene graft copolymer for later use.

[0078] (3) Polylactic acid, high grafting rate random copolymer polypropylene graft copolymer obtained in step (2), azobisisobutyronitrile, and dibutyl ivonate are uniformly mixed and melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded strips are cooled with water and then granulated for later use.

[0079] The polylactic acid / random copolymer polypropylene blend obtained in step (3) was injection molded into tensile specimens and impact specimens using a micro injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard, using an impact hammer with an energy of 2.75 J and a test temperature of 23℃. Example 2

[0080] 50 parts of polylactic acid

[0081] 25 parts of random copolymer polypropylene (NS06)

[0082] 25 parts of polypropylene-based elastomer (Versify 2300)

[0083] 4 parts maleic anhydride

[0084] 8 parts of α-methylstyrene

[0085] 5 parts of dibutyl ioconate

[0086] 0.2 parts of dicumyl peroxide

[0087] (1) Random copolymer polypropylene and polypropylene-based elastomer are uniformly mixed at a mass ratio of 5:5 and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then pelletized to obtain a random copolymer polypropylene / polypropylene-based elastomer blend for later use.

[0088] (2) The blend obtained in step (1) is uniformly mixed with maleic anhydride, α-methylstyrene and dicumyl peroxide and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then granulated to obtain a high grafting rate random copolymer polypropylene graft copolymer for later use.

[0089] (3) Polylactic acid, high grafting rate random copolymer polypropylene graft copolymer obtained in step (2), dicumyl peroxide and dibutyl ivonate are uniformly mixed and melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded strips are cooled with water and then granulated for later use.

[0090] The polylactic acid / random copolymer polypropylene blend obtained in step (3) was injection molded into tensile specimens and impact specimens using a micro injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard, using an impact hammer with an energy of 2.75 J and a test temperature of 23℃. Example 3

[0091] 60 parts of polylactic acid

[0092] 25 parts of random copolymer polypropylene (Hifax CA10A)

[0093] 15 parts of polypropylene-based elastomer (Versify 2300)

[0094] 4 parts maleic anhydride

[0095] 8 parts of α-methylstyrene

[0096] 5 parts of dibutyl ioconate

[0097] 0.2 parts of dicumyl peroxide

[0098] (1) Random copolymer polypropylene and polypropylene-based elastomer are uniformly mixed at a mass ratio of 5:5 and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then pelletized to obtain a random copolymer polypropylene / polypropylene-based elastomer blend for later use.

[0099] (2) The blend obtained in step (1) is uniformly mixed with maleic anhydride, α-methylstyrene and dicumyl peroxide and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then granulated to obtain a high grafting rate random copolymer polypropylene graft copolymer for later use.

[0100] (3) Polylactic acid, random copolymer polypropylene, high grafting rate random copolymer polypropylene graft copolymer obtained in step (2), dicumyl peroxide and dibutyl ivonate are uniformly mixed and melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded strip is cooled with water and then granulated for later use.

[0101] The polylactic acid / random copolymer polypropylene blend obtained in step (3) was injection molded into tensile specimens and impact specimens using a micro injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard, using an impact hammer with an energy of 2.75 J and a test temperature of 23℃. Example 4

[0102] 70 parts of polylactic acid

[0103] 24 parts of random copolymer polypropylene (Hifax CA10A)

[0104] 6 parts of polypropylene-based elastomer (Versify 2300)

[0105] 4 parts maleic anhydride

[0106] 8 parts of α-methylstyrene

[0107] 5 parts of dibutyl ioconate

[0108] 0.2 parts of dicumyl peroxide

[0109] (1) Random copolymer polypropylene and polypropylene-based elastomer are uniformly mixed at a mass ratio of 8:2 and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then granulated to obtain a random copolymer polypropylene / polypropylene-based elastomer blend for later use.

[0110] (2) The blend obtained in step (1) is uniformly mixed with maleic anhydride, α-methylstyrene and dicumyl peroxide and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then granulated to obtain a high grafting rate random copolymer polypropylene graft copolymer for later use.

[0111] (3) Polylactic acid, high grafting rate random copolymer polypropylene graft copolymer obtained in step (2), dicumyl peroxide and dibutyl ivonate are uniformly mixed and melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded strips are cooled with water and then granulated for later use.

[0112] The polylactic acid / random copolymer polypropylene blend obtained in step (3) was injection molded into tensile specimens and impact specimens using a micro injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard, using an impact hammer with an energy of 2.75 J and a test temperature of 23℃. Example 5

[0113] 75 parts of polylactic acid

[0114] 21 parts of random copolymer polypropylene (NS06)

[0115] 4 parts of polypropylene-based elastomer (Versify 2300)

[0116] 4 parts glycidyl methacrylate

[0117] 8 parts of styrene

[0118] Citric acid 5 parts

[0119] 0.2 parts of dicumyl peroxide

[0120] (1) Random copolymer polypropylene and polypropylene-based elastomer are uniformly mixed at a mass ratio of 8:2 and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then granulated to obtain a random copolymer polypropylene / polypropylene-based elastomer blend for later use.

[0121] (2) The blend obtained in step (1) is uniformly mixed with glycidyl methacrylate, styrene and dicumyl peroxide and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. After the extruded sample is cooled with water, it is granulated to obtain a high grafting rate random copolymer polypropylene graft copolymer for later use.

[0122] (3) Polylactic acid, high grafting rate random copolymer polypropylene graft copolymer obtained in step (2), dicumyl peroxide and citric acid are uniformly mixed and melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded strip is cooled with water and then granulated for later use.

[0123] The polylactic acid / random copolymer polypropylene blend obtained in step (3) was injection molded into tensile specimens and impact specimens using a micro injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard, using an impact hammer with an energy of 2.75 J and a test temperature of 23℃. Example 6

[0124] 80 parts of polylactic acid

[0125] 16 parts of random copolymer polypropylene (NS06)

[0126] 4 parts of polypropylene-based elastomer (Versify 2300)

[0127] 4 parts glycidyl methacrylate

[0128] 8 parts of styrene

[0129] Citric acid 5 parts

[0130] 0.2 parts of cumene hydroperoxide

[0131] (1) Random copolymer polypropylene and polypropylene-based elastomer are uniformly mixed at a mass ratio of 8:2 and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded sample is cooled with water and then granulated to obtain a random copolymer polypropylene / polypropylene-based elastomer blend for later use.

[0132] (2) The blend obtained in step (1) is uniformly mixed with glycidyl methacrylate, styrene and dicumyl peroxide and then melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. After the extruded sample is cooled with water, it is granulated to obtain a high grafting rate random copolymer polypropylene graft copolymer for later use.

[0133] (3) Polylactic acid, high grafting rate random copolymer polypropylene graft copolymer obtained in step (2), cumene hydroperoxide and citric acid are uniformly mixed and melt-blended in a twin-screw extruder. The temperature of each section of the extruder is set to 180-200℃ and the screw speed is 200-250r / min. The extruded strip is cooled with water and then granulated for later use.

[0134] The polylactic acid / random copolymer polypropylene blend obtained in step (3) was injection molded into tensile specimens and impact specimens using a micro injection molding machine. Tensile properties were tested according to GB / T 528-2009 standard at a test speed of 50 mm / min. Impact tests were conducted according to GB / T1843 / 1-A standard, using an impact hammer with an energy of 2.75 J and a test temperature of 23℃.

[0135] Table 1. Impact strength and elongation at break of comparative and example examples

[0136] impact strength (J / m 2 ) elongation at break (%) comparative example 1 3340.4 8.2 comparative example 2 3542.2 10.1 comparative example 3 3624.5 7.4 comparative example 4 3423.5 12.1 comparative example 5 4218.7 11.0 comparative example 6 5442.6 32.3 comparative example 7 5271.8 45.6 example 1 8723.5 121.9 example 2 9213.4 134.1 example 3 8973.9 140.2 example 4 9782.8 141.5 example 5 9342.3 128.9 example 6 10037.3 137.6

[0137] As can be seen from the results in Table 1 above, the present invention prepares a high-toughness polylactic acid / random copolymer polypropylene blend by efficiently grafting random copolymer polypropylene / polypropylene-based elastomer blend and then synergistically combining it with a compatibilizer.

[0138] The embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a high-toughness polylactic acid random copolymer polypropylene blend, characterized in that, The preparation process of the high-graft-rate random copolymer polypropylene graft copolymer involves first blending the random copolymer polypropylene with a polypropylene-based elastomer, followed by grafting treatment; the method includes the following preparation steps: (1) Random copolymer polypropylene and polypropylene-based elastomer are melt-blended, and then grafting monomer, co-grafting monomer and initiator are added for melt blending to prepare random copolymer polypropylene graft copolymer with high grafting rate; the mass ratio of random copolymer polypropylene and polypropylene-based elastomer is 9:1-5:5, grafting monomer is 1-5 parts, co-grafting monomer is 2-10 parts and initiator is 0.1-0.5 parts; (2) Preparation of blended materials: Before melt processing, the sample needs to be placed in a vacuum oven and dried under the required conditions; polylactic acid, random copolymer polypropylene, high grafting rate random copolymer polypropylene graft copolymer obtained in step (1), compatibilizer, and initiator are mixed uniformly in the required proportion and then melt-blended in a twin-screw extruder to prepare a polylactic acid / random copolymer polypropylene blended material with high toughness; The blend consists of 50-90 parts polylactic acid, 0-50 parts random copolymer polypropylene, 10-50 parts high-graft-rate random copolymer polypropylene graft copolymer, 1-15 parts compatibilizer, and 0.1-0.5 parts initiator. The melt index of the polypropylene-based elastomer is 2-4 g / 10 min at 190℃ for 2.16 kg, the polyethylene content is 5-25%, and the polypropylene content is 75-95%. The grafting monomer is at least one of glycidyl methacrylate, maleic anhydride, methyl methacrylate, butyl acrylate, and vinyl alcohol; the grafting agent is one or more of styrene, α-methylstyrene, acrylic acid, and dimethylformamide; and the initiator is one or more of azobisisobutyronitrile, dicumyl peroxide, cumyl hydroperoxide, and benzoyl peroxide. The compatibilizer is at least one of itaconic acid, dibutyl itaconic acid, succinic acid, salicylic acid, and citric acid.