A method for preparing maleic anhydride grafted polypropylene by microwave-melting grafting

Abstract

The present invention provides a method for preparing maleic anhydride grafted polypropylene by microwave-melt grafting, which comprises the following steps: (1) mixing an initiator, maleic anhydride and polypropylene uniformly; (2) irradiating the reaction system obtained by mixing in step (1) with microwave for a period of time to obtain a microwave grafted product of polypropylene-maleic anhydride; (3) immediately after the reaction in step (2) is completed, putting the reacted mixed system into an extruder for melt grafting to obtain a maleic anhydride grafted polypropylene product. The grafting rate of the maleic anhydride grafted polypropylene prepared by the present invention is 0.30-2.50%. The preparation method of the present invention does not need to input auxiliary monomers, which eliminates the odor problem generated by the traditional melt grafting process; by controlling the two processes of microwave reaction and melt grafting reaction simultaneously, different performance requirements for maleic anhydride grafted polypropylene are met; and the microwave grafting does not require a swelling process, which is beneficial to industrial promotion.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and particularly relates to a method for preparing maleic anhydride grafted polypropylene by combined microwave-melt grafting. Background Art

[0002] Polypropylene is a colorless, semi-transparent thermoplastic lightweight general-purpose plastic with a low density (0.89 - 0.91 g / cm3), making it one of the lightest plastics. The melting point of polypropylene reaches 165°C and it can be used for a long time at 100°C - 120°C. Due to its excellent properties, polypropylene has a relatively broad market prospect in fields such as textiles, papermaking, chemical industry, coal, petroleum, transportation, medical treatment, ships, national defense, and aerospace.

[0003] Maleic anhydride grafted polypropylene (PP-g-MAH) is a compatibilizer that can enable good mixing of polypropylene with other additives. With the development of technology, polymer materials have been increasingly widely applied in various fields. However, single polymers are difficult to meet the market demands. Therefore, alloying or modifying high polymers has attracted more and more attention. However, due to the polarity differences between various polymers or between polymers and filler reinforcing agents, they cannot be well compatible, thus affecting the product performance and restricting their applications. Therefore, solving the compatibility becomes the key to the problem. The common solution is to add PP-g-MAH.

[0004] The research on graft-modifying polypropylene with maleic anhydride (MAH) (PP-g-MAH) has been highly regarded both at home and abroad. Such research has started since the 1960s. As long as 5% of maleic anhydride grafted polypropylene is added, the adhesion between polypropylene and inorganic fillers such as glass fiber, talc powder, and mica can be greatly improved, and the tensile strength, flexural strength, impact strength, etc. of the modified polypropylene can be significantly increased. PP-g-MAH is widely used as a compatibilizer for polypropylene and resins containing polar groups in alloys.

[0005] The methods for maleic anhydride grafted polypropylene mainly include melt grafting method, solution grafting method, solid phase method, suspension grafting method, radiation grafting method, solid phase mechanochemistry grafting method, supercritical CO2 fluid method, solid phase-melt grafting method. The melt grafting method is the main one that can be successfully industrialized. In this method, the formulation (polypropylene, maleic anhydride, initiator) is mixed and then put into an extruder for extrusion to obtain PP-g-MAH. This method is simple and efficient and can be continuously produced. However, for the PP-g-MAH obtained by this method, the grafting rate is generally low, and a large amount of maleic anhydride monomer remains, resulting in waste. The general method to increase the grafting rate in the melt grafting process is to add auxiliary grafting monomers, including styrene, acrylic acid, acrylonitrile, glycidyl methacrylate, etc. However, these monomers are generally toxic, harmful and have pungent odors. During the melt extrusion process, the monomers cannot be effectively removed, ultimately leading to odor problems in the product.

[0006] There are many existing patents and literature reports on the methods and formulations for preparing PP-g-MAH by melt extrusion method. Most of them have innovations in the selection of auxiliary grafting monomers or add other substances to assist in devolatilization. Patent CN108892752 discloses a low-odor graft compatibilizer and its preparation method. The compatibilizer prepared by replacing part of maleic anhydride with octenyl succinic anhydride has the effect of lower odor while ensuring the melt strength. Patent CN109535327 discloses a maleic anhydride grafted polypropylene composition and its preparation method. By adding 0.05-0.2 parts of deodorant, the finally obtained PP-g-MAH has low volatility, little product odor, high melt index, good fluidity and excellent processing performance. Patent CN104804143 discloses a preparation method of maleic anhydride grafted polypropylene. The initiator and the auxiliary monomer styrene are formulated into a solution and added at different screw barrel sections of a twin-screw extruder, and the reaction time is extended to increase the grafting rate of PP-g-MAH prepared by the melt extrusion method. Patent CN102321217 discloses a copolymer of melt polypropylene grafted with maleic anhydride and its preparation method. It introduces the second comonomer limonene to increase the grafting rate of PP-g-MAH and reduce odor problems. Patent CN1456430 discloses a preparation method of a polypropylene grafted maleic anhydride compatibilizer, which solves the odor problem by introducing oleic acid instead of styrene.

[0007] Obviously, after adding auxiliary grafting monomers, the grafting rate of PP-g-MAH prepared by the melt grafting method can be greatly increased, which can be increased from 0.5% to about 1.0%. However, the auxiliary grafting monomers bring odor problems. How to solve this contradictory problem has been a research hotspot of PP-g-MAH prepared by the melt grafting method in recent years.

[0008] The microwave grafting method is an auxiliary grafting method that emerged in the past decade or so. It can also be used in the preparation process of PP-g-MAH. The principle is that PP has microwave transparency, while MAH can absorb microwaves to heat up and undergo a grafting reaction with polypropylene. However, the following problems have emerged: (1) If the MAH powder and PP powder are directly grafted, due to factors such as low mixing degree and easy volatilization of MAH when heated, the final grafting rate is low, about 0.3%, and uneven heat dissipation easily leads to partial melting of polypropylene. (2) Swelling followed by microwave treatment mentioned in the literature or patents can effectively improve the grafting rate. The principle is that MAH is mixed evenly with PP along with the swelling interface agent, but the method cannot be industrialized due to the difficulty in removing the interface agent. Patent CN 112694567 discloses a method for microwave-assisted polypropylene grafting, in which styrene, maleic anhydride, and initiator are dissolved in the interface agent, and then added to the xylene swelling body of polypropylene. After mixing well, microwave irradiation is carried out, and the grafting rate can reach about 1.2%. This type of method also appears in Chinese and foreign literature, but the post-treatment problems involved in the swelling method have always been a major obstacle to its industrialization and also a major problem in the industrialization of microwave grafting technology.

[0009] In summary, how to use the melt grafting method to industrially produce PP-g-MAH without generating odor problems and complex post-treatment problems will be the key research direction in this field. Summary of the Invention

[0010] In order to overcome the deficiencies of the current technology, the present invention provides a method for preparing maleic anhydride-grafted polypropylene using a microwave-melt grafting combined technology, so as to provide a more suitable method for industrial production of maleic anhydride-grafted polypropylene.

[0011] To achieve the above object, the present invention adopts the following technical solutions:

[0012] A method for preparing maleic anhydride-grafted polypropylene by microwave-melt grafting, the method comprising the following steps:

[0013] (1) Mix the initiator, maleic anhydride, and polypropylene evenly;

[0014] (2) Microwave irradiate the reaction system after mixing in step (1) for a period of time to obtain a polypropylene-maleic anhydride microwave grafted product;

[0015] (3) After the reaction in step (2) is completed, immediately put the reacted mixed system into an extruder for a melt grafting process to obtain maleic anhydride-grafted polypropylene.

[0016] In the above technical solution, maleic anhydride grafted polypropylene is prepared by combining microwave grafting and melt grafting technologies. First, each raw material component is mixed at high speed, and then irradiated under microwave conditions for a period of time to obtain a polypropylene microwave grafted product. Immediately after that, the product is put into an extruder for further melt grafting to finally obtain a polypropylene grafted product with a high grafting rate.

[0017] The present invention is further preferably that the initiator includes one or more of azo initiators or peroxide initiators.

[0018] The present invention is further preferably that the initiator is selected from one or more of benzoyl peroxide (BPO), tert-butyl peroxybenzoate (TBP), azobisisobutyronitrile (AIBN), bis(tert-butylperoxy)diisopropylbenzene (BIPB), or dicumyl peroxide (DCP). Preferably, the initiator is bis(tert-butylperoxy)diisopropylbenzene or dicumyl peroxide.

[0019] The present invention is further preferably that the polypropylene is selected from one or more of homopolypropylene, block copolymerized polypropylene, and random copolymerized polypropylene.

[0020] The present invention is further preferably that the polypropylene is polypropylene without antioxidant.

[0021] The present invention is further preferably that in step (1), the mass ratio of maleic anhydride in the system is 1-10%, and the mass ratio of the initiator in the system is 0.1-0.4%.

[0022] The present invention is further preferably that in step (1), the mass ratio of maleic anhydride in the system is 1-5%.

[0023] The present invention is further preferably that in step (1), the initiator, maleic anhydride, and polypropylene are put into a high-speed mixer for mixing. During the mixing process, the rotation speed of the high-speed mixer is 25000-35000 r / min, and the mixing time is 1-10 min.

[0024] The present invention is further preferably that in step (2), the mixed system is put into a sealed glass dish for microwave irradiation. The power of the microwave irradiation is 100-1000 W, and the time of the microwave irradiation is 1-60 min;

[0025] The present invention is further preferably that the microwave irradiation power is 500-1000 W, and the irradiation time is 1-10 min.

[0026] The present invention is further preferably that in step (3), melt grafting is carried out by a twin-screw extruder, and the temperatures of the melting section and the natural exhaust section of the twin-screw extruder are 170-280 °C; the rotational speed of the main screw of the twin-screw extruder is 100-300 r / min, the rotational speed of the feeding screw is 10-50 r / min, and the ratio of the rotational speed of the main screw to the rotational speed of the feeding screw is ≥10:1.

[0027] The present invention is further preferably that the temperatures of the melting section and the natural exhaust section of the extruder are 180-210 °C; the feeding ratio is preferably 10:1.

[0028] The present invention is further preferably that maleic anhydride grafted polypropylene is prepared by the method, and the grafting rate of maleic anhydride is 0.3%-2.50%; preferably 0.8%-1.95%.

[0029] The present invention also provides a maleic anhydride grafted polypropylene prepared by the above preparation method.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) In the present invention, microwave irradiation is used to assist the grafting of polypropylene in sequence, and then melt grafting is continued. In this process, no auxiliary grafting monomer needs to be added, and maleic anhydride grafted polypropylene with a high grafting rate can be prepared, which not only reduces the production cost but also solves the product odor problem from the source.

[0032] (2) By using the polypropylene grafting method of the present invention, the utilization rate of maleic anhydride monomer can be greatly improved. By adopting the technical scheme of the present invention, when maleic anhydride ≤5%, the grafting rate of maleic anhydride can still be >2.0%.

[0033] (3) In the method of the present invention, the powder is directly grafted during the microwave-assisted process without going through a swelling process, which solves the solvent problem caused by swelling and does not require post-treatment; and during the process, the raw materials do not need to be treated either, and the next-step melt grafting can be carried out. The preparation process is easy to operate and is conducive to industrial promotion. Description of the Drawings

[0034] Figure 1 It is a schematic structural diagram of the twin-screw extruder used in the examples. Detailed Embodiments

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work shall fall within the protection scope of the present invention.

[0036] The present invention provides a method for preparing maleic anhydride grafted polypropylene by microwave-melt grafting. This method combines microwave grafting and melt grafting techniques to prepare maleic anhydride grafted polypropylene, and specifically includes the following steps:

[0037] (1) Mix the initiator, maleic anhydride and polypropylene until homogeneous;

[0038] (2) Irradiate the reaction system obtained by mixing in step (1) with microwave for a period of time to obtain a microwave grafted product of polypropylene-maleic anhydride;

[0039] (3) After the reaction in step (2) is completed, immediately put the reacted mixed system into an extruder for melt grafting process to obtain maleic anhydride grafted polypropylene.

[0040] In the present invention, the polypropylene includes but is not limited to at least one of homopolypropylene, random copolymer polypropylene, and block copolymer polypropylene.

[0041] In the present invention, the polypropylene resin includes powder, pellet or solid form of products, and is preferably polypropylene powder. The polypropylene powder is preferably obtained from industrial products polymerized by Ziegler-Natta catalyst, metallocene catalyst or non-metallocene transition metal catalyst.

[0042] Furthermore, the polypropylene is preferably polypropylene without antioxidant.

[0043] It should be noted that in the specific embodiments of the present invention, the initiator, maleic anhydride and polypropylene used are all directly purchased. The present invention uses polypropylene powder. Among them, homopolypropylene (iPP) is selected as PPH-045, purchased from Zhejiang Hongji Petrochemical; random copolymer polypropylene is selected as PPR-T4401, purchased from Maoming Petrochemical; block copolymer polypropylene is selected as block polypropylene C180, purchased from Yangzi Petrochemical.

[0044] In the specific embodiments of the present invention, the twin-screw extruder used is purchased from Nanjing Rubber and Plastic Factory, and the model is HT-35. The structure of this twin-screw extruder is as Figure 1 shown. There are a total of 8 temperature zones numbered 1-8 and a head zone numbered 9 from left to right. Among them, the melting section and the natural exhaust section of the extruder are the temperature zones numbered 3-6. Considering that the PP is not melted in the temperature sections numbered 1-2 and the reaction is terminated due to forced exhaust in the zone numbered 8, it has no obvious influence on the grafting reaction.

[0045] The method of the present invention will be further described below through specific examples.

[0046] Example 1

[0047] Take 0.6 g of initiator BIPB, 15 g of maleic anhydride and 300 g of homopolypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30,000 r / min. After mixing, take the mixture and place it in a closed glass dish, irradiate it in a microwave reactor at 700 w for 5 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1 shown. Set the temperatures of the 1st - 8th sections of the twin-screw extruder to be 140 °C, 160 °C, 180 °C, 180 °C, 180 °C, 180 °C, 180 °C, 180 °C respectively, the temperature of the head section is 180 °C, the rotational speed of the main screw of the host is 180 r / min, and the rotational speed of the feeding screw is 18 r / min. PP-g-MAH is prepared, and the grafting rate G of maleic anhydride is 1.9543%.

[0048] Comparative Example 1

[0049] Take 0.6 g of initiator BIPB, 15 g of maleic anhydride and 300 g of homopolypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30,000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 700 w for 5 min and then take it out to prepare PP-g-MAH, and the grafting rate G of maleic anhydride is 1.2215%.

[0050] Example 2

[0051] Take 0.6 g of initiator DCP, 20 g of maleic anhydride and 300 g of homopolypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30,000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 600 w for 6 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1 shown. Set the temperatures of the 1st - 8th sections of the twin-screw extruder to be 140 °C, 160 °C, 180 °C, 180 °C, 180 °C, 180 °C, 180 °C, 180 °C respectively, the head temperature is 180 °C, the rotational speed of the main screw of the host is 180 r / min, and the rotational speed of the feeding screw is 18 r / min. PP-g-MAH is prepared, and the calculated grafting rate G is 2.1223%.

[0052] Comparative Example 2

[0053] Take 0.6 g of initiator DCP, 20 g of maleic anhydride and 300 g of homopolypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30,000 r / min. After mixing, immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1As shown, the temperatures of the 1st to 8th zones of the twin-screw extruder are set at 140°C, 160°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 180 r / min, and the feeding screw rotation speed is 18 r / min. PP-g-MAH is prepared, and the grafting rate G = 0.6219%.

[0054] Example 3

[0055] Take 0.9 g of initiator BIPB, 25 g of maleic anhydride, and 250 g of homopolypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 800 w for 6 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1 As shown, the temperatures of the 1st to 8th zones of the twin-screw extruder are set at 140°C, 160°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 180 r / min, and the feeding screw rotation speed is 18 r / min. PP-g-MAH is prepared, and the grafting rate G = 2.4477%.

[0056] Comparative Example 3

[0057] Take 0.9 g of initiator BIPB, 2.5 g of maleic anhydride, and 250 g of homopolypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 800 w for 6 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1 As shown, the temperatures of the 1st to 8th zones of the twin-screw extruder are set at 140°C, 160°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 180 r / min, and the feeding screw rotation speed is 18 r / min. PP-g-MAH is prepared, and the grafting rate G = 0.8325%.

[0058] Example 4

[0059] Take 0.9 g of initiator DCP, 15 g of maleic anhydride, and 300 g of block copolymerized polypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 900 w for 4 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1As shown in the figure, the temperatures of the 1st to 8th sections of the twin-screw extruder are set to 140 °C, 160 °C, 200 °C, 200 °C, 200 °C, 200 °C, 180 °C, 180 °C respectively, the temperature of the die head is 180 °C, the rotational speed of the main screw of the host is 180 r / min, and the rotational speed of the feeding screw is 18 r / min. PP-g-MAH is prepared, and the grafting rate G = 1.8341%.

[0060] Comparative Example 4

[0061] Take 0.3 g of initiator DCP, 15 g of maleic anhydride, and 300 g of block copolymerized polypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30,000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 900 w for 4 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1 As shown in the figure, the temperatures of the 1st to 8th sections of the twin-screw extruder are set to 140 °C, 160 °C, 200 °C, 200 °C, 200 °C, 200 °C, 180 °C, 180 °C respectively, the temperature of the die head is 180 °C, the rotational speed of the main screw of the host is 180 r / min, and the rotational speed of the feeding screw is 18 r / min. PP-g-MAH is prepared, and the grafting rate G = 1.1315%.

[0062] Example 5

[0063] Take 0.9 g of initiator BIPB, 18 g of maleic anhydride, and 350 g of block copolymerized polypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30,000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 1000 w for 5 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1 As shown in the figure, the temperatures of the 1st to 8th sections of the twin-screw extruder are set to 140 °C, 160 °C, 200 °C, 200 °C, 200 °C, 200 °C, 180 °C, 180 °C respectively, the temperature of the die head is 180 °C, the rotational speed of the main screw of the host is 120 r / min, and the rotational speed of the feeding screw is 12 r / min. PP-g-MAH is prepared, and the grafting rate G = 2.2886%.

[0064] Comparative Example 5

[0065] Take 0.9 g of initiator BIPB, 18 g of maleic anhydride, and 350 g of block copolymerized polypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30,000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 100 w for 5 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1As shown, the temperatures of the 1st - 8th zones of the twin - screw extruder are set at 140°C, 160°C, 200°C, 200°C, 200°C, 200°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw speed of the host is 120 r / min, and the feeding screw speed is 12 r / min. PP - g - MAH is prepared, and the grafting rate G = 1.2839%.

[0066] Example 6

[0067] Take 0.4 g of initiator BIPB, 17 g of maleic anhydride, and 300 g of block - copolymerized polypropylene, place them in a high - speed mixer, mix for 3 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a sealed glass dish, heat it in a microwave reactor at 600 w for 10 min, then take it out and immediately put it into a twin - screw extruder for extrusion. The structure of the twin - screw extruder is as Figure 1 As shown, the temperatures of the 1st - 8th zones of the twin - screw extruder are set at 140°C, 160°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw speed of the host is 200 r / min, and the feeding screw speed is 20 r / min. PP - g - MAH is prepared, and the grafting rate G = 1.8033%.

[0068] Comparative Example 6

[0069] Take 0.4 g of initiator BIPB, 17 g of maleic anhydride, and 300 g of block - copolymerized polypropylene, place them in a high - speed mixer, mix for 30 s under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a sealed glass dish, heat it in a microwave reactor at 600 w for 10 min, then take it out and immediately put it into a twin - screw extruder for extrusion. The structure of the twin - screw extruder is as Figure 1 As shown, the temperatures of the 1st - 8th zones of the twin - screw extruder are set at 140°C, 160°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw speed of the host is 200 r / min, and the feeding screw speed is 20 r / min. PP - g - MAH is prepared, and the grafting rate G = 1.3259%.

[0070] Example 7

[0071] Take 0.6 g of initiator BIPB, 15 g of maleic anhydride, and 300 g of random - copolymerized polypropylene, place them in a high - speed mixer, mix for 3 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a sealed glass dish, heat it in a microwave reactor at 800 w for 5 min, then take it out and immediately put it into a twin - screw extruder for extrusion. The structure of the twin - screw extruder is as Figure 1As shown in the figure, the temperatures of the 1st - 8th sections of the twin - screw extruder are set to 140°C, 160°C, 210°C, 210°C, 210°C, 210°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 200 r / min, and the feeding screw rotation speed is 20 r / min. PP - g - MAH is prepared, and the grafting rate G = 2.0752%.

[0072] Comparative Example 7

[0073] Take 0.6 g of initiator BIPB, 15 g of maleic anhydride, and 300 g of random copolymerized polypropylene, place them in a high - speed mixer, mix for 3 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a sealed glass dish, heat it in a microwave reactor at 800 w for 5 min and then take it out, and immediately put it into a twin - screw extruder for extrusion. The structure of the twin - screw extruder is as Figure 1 shown. The temperatures of the 1st - 8th sections of the twin - screw extruder are set to 140°C, 160°C, 210°C, 210°C, 210°C, 210°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 500 r / min, and the feeding screw rotation speed is 50 r / min. PP - g - MAH is prepared, and the grafting rate G = 1.4571%.

[0074] Example 8

[0075] Take 0.7 g of initiator DCP, 12 g of maleic anhydride, and 420 g of random copolymerized polypropylene, place them in a high - speed mixer, mix for 5 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a sealed glass dish, heat it in a microwave reactor at 600 w for 10 min and then take it out, and immediately put it into a twin - screw extruder for extrusion. The structure of the twin - screw extruder is as Figure 1 shown. The temperatures of the 1st - 8th sections of the twin - screw extruder are set to 140°C, 160°C, 240°C, 240°C, 240°C, 240°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 160 r / min, and the feeding screw rotation speed is 16 r / min. PP - g - MAH is prepared, and the grafting rate G = 1.9465%.

[0076] Comparative Example 8

[0077] Take 0.7 g of initiator DCP, 12 g of maleic anhydride, and 420 g of random copolymerized polypropylene, place them in a high - speed mixer, mix for 5 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a sealed glass dish, heat it in a microwave reactor at 600 w for 1 min and then take it out, and immediately put it into a twin - screw extruder for extrusion. The structure of the twin - screw extruder is as Figure 1As shown, the temperatures of the 1st to 8th zones of the twin-screw extruder are set to 140°C, 160°C, 240°C, 240°C, 240°C, 240°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 180 r / min, and the feeding screw rotation speed is 18 r / min. PP-g-MAH is prepared, and the grafting rate G = 1.1439%.

[0078] Example 9

[0079] Take 0.6 g of initiator BIPB, 14 g of maleic anhydride, and 300 g of random copolymerized polypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 800 w for 5 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1 As shown, the temperatures of the 1st to 8th zones of the twin-screw extruder are set to 140°C, 160°C, 280°C, 280°C, 280°C, 280°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 180 r / min, and the feeding screw rotation speed is 18 r / min. PP-g-MAH is prepared, and the grafting rate G = 1.8698%.

[0080] Example 10

[0081] Take 0.6 g of initiator BIPB, 14 g of maleic anhydride, and 300 g of random copolymerized polypropylene, place them in a high-speed mixer, mix for 3 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 800 w for 5 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1 As shown, the temperatures of the 1st to 8th zones of the twin-screw extruder are set to 140°C, 160°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 180 r / min, and the feeding screw rotation speed is 18 r / min. PP-g-MAH is prepared, and the grafting rate G = 2.0325%.

[0082] Example 11

[0083] Take 0.8 g of initiator BIPB, 19 g of maleic anhydride, and 400 g of random copolymerized polypropylene, place them in a high-speed mixer, mix for 1 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a closed glass dish, heat it in a microwave reactor at 1000 w for 8 min and then take it out, and immediately put it into a twin-screw extruder for extrusion. The structure of the twin-screw extruder is as Figure 1As shown, the temperatures of the 1st - 8th zones of the twin - screw extruder are set at 140°C, 160°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 300 r / min, and the feeding screw rotation speed is 30 r / min. PP - g - MAH is prepared, and the grafting rate G = 1.7258%.

[0084] Example 12

[0085] Take 0.8 g of initiator BIPB, 19 g of maleic anhydride, and 400 g of random copolymerized polypropylene, place them in a high - speed mixer, mix for 3 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a sealed glass dish, heat it in a microwave reactor at 1000 w for 8 min and then take it out, and immediately put it into a twin - screw extruder for extrusion. The structure of the twin - screw extruder is as Figure 1 shown. The temperatures of the 1st - 8th zones of the twin - screw extruder are set at 140°C, 160°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 100 r / min, and the feeding screw rotation speed is 10 r / min. PP - g - MAH is prepared, and the grafting rate G = 1.8651%.

[0086] Example 13

[0087] Take 0.8 g of initiator BIPB, 20 g of maleic anhydride, and 400 g of random copolymerized polypropylene, place them in a high - speed mixer, mix for 3 min under the condition of a mixing speed of 30000 r / min. After mixing, take the mixture and place it in a sealed glass dish, heat it in a microwave reactor at 1000 w for 8 min and then take it out, and immediately put it into a twin - screw extruder for extrusion. The structure of the twin - screw extruder is as Figure 1 shown. The temperatures of the 1st - 8th zones of the twin - screw extruder are set at 140°C, 160°C, 170°C, 170°C, 170°C, 170°C, 180°C, 180°C respectively, the head temperature is 180°C, the main screw rotation speed of the host is 180 r / min, and the feeding screw rotation speed is 18 r / min. PP - g - MAH is prepared, and the grafting rate G = 1.8368%.

[0088] Example 14

[0089] Take 0.8 g of initiator BIPB, 19 g of maleic anhydride, and 400 g of random copolymerized polypropylene, place them in a high - speed mixer, mix for 10 min under the condition of a mixing speed of 30000 revolutions per minute. After mixing, take the mixture and place it in a sealed glass dish, heat it in a microwave reactor at 1000 w for 8 min and then take it out, and immediately put it into a twin - screw extruder for extrusion. The structure of the twin - screw extruder is as Figure 1As shown, the temperatures of the 1st to 8th zones of the twin-screw extruder are set to 140°C, 160°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C respectively, and the head temperature is 180°C. The rotational speed of the main screw is 180 r / min, and the rotational speed of the feeding screw is 18 r / min. PP-g-MAH is prepared, and the grafting rate G = 1.9157%.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing maleic anhydride grafted polypropylene by microwave-melting grafting, characterized in that, The method comprises the following steps: (1) Mix an initiator, maleic anhydride and polypropylene until homogeneous; (2) Microwave irradiate the reaction system after mixing in step (1) for a period of time to obtain a microwave grafted product of polypropylene - maleic anhydride; (3) After the reaction in step (2) is completed, immediately put the reacted mixed system into an extruder for a melt grafting process to obtain maleic anhydride grafted polypropylene; Among them, in step (1), the initiator, maleic anhydride and polypropylene are put into a high - speed mixer for mixing. The rotation speed of the high - speed mixer is 25000 - 35000 r / min, and the mixing time is 1 - 10 min; the mass ratio of maleic anhydride in the system is 1 - 10%, and the mass ratio of the initiator in the system is 0.1 - 0.4%; In step (2), the power of the microwave irradiation is 500 - 1000 W, and the time of the microwave irradiation is 4 - 60 min; In step (3), a twin - screw extruder is used for melt grafting. The rotation speed of the main screw of the extruder is 100 - 300 r / min, and the rotation speed of the feeding screw is 10 - 50 r / min.

2. The method for preparing maleic anhydride grafted polypropylene by microwave-melting grafting according to claim 1, wherein The initiator includes one or more of azo - type initiators or peroxide - type initiators.

3. A method for preparing maleic anhydride grafted polypropylene by microwave-melting grafting according to claim 2, characterized in that, The initiator is selected from one or more of benzoyl peroxide, tert - butyl peroxyformate, azobisisobutyronitrile, ditert - butyl peroxide diisopropylbenzene or diisopropylbenzene peroxide.

4. A method for preparing maleic anhydride grafted polypropylene by microwave-melting grafting according to claim 1, characterized in that, The polypropylene is selected from one or more of homopolypropylene, block copolymerized polypropylene and random copolymerized polypropylene.

5. A method for preparing maleic anhydride grafted polypropylene by microwave-melting grafting according to claim 1, characterized in that, In step (1), the mass ratio of maleic anhydride in the system is 1 - 5%.

6. A method for preparing maleic anhydride grafted polypropylene by microwave-melting grafting according to claim 1, characterized in that, In step (2), the reaction system after mixing in step (1) is put into a sealed glass dish for microwave irradiation.

7. A method for preparing maleic anhydride grafted polypropylene by microwave-melting grafting according to claim 1, characterized in that, In step (3), the temperature of the melting section and the natural exhaust section of the twin - screw extruder is 170 - 280 °C.

8. A method for preparing maleic anhydride grafted polypropylene by microwave-melting grafting according to claim 1, characterized in that, Using the said method to prepare maleic anhydride grafted polypropylene, the grafting rate of maleic anhydride is 0.3% - 2.50%.

9. A method for preparing maleic anhydride grafted polypropylene by microwave-melting grafting according to claim 8, characterized in that, Using the said method to prepare maleic anhydride grafted polypropylene, the grafting rate of maleic anhydride is 0.8% - 1.95%.

10. A maleic anhydride grafted polypropylene prepared by the method according to any one of claims 1 - 9.

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