A method for improving the compatibility of PE / PP blends based on ozone and the obtained product

Abstract

The present invention discloses a method for improving the compatibility of PE / PP alloy based on ozone and the obtained product. The method comprises the following steps: using a PE / PP blend as a raw material, an ozone generator as an ozone source, and an extruder with functions of gas inlet and outlet as a reaction device. First, the PE / PP blend is added through the feed port of the extruder, melted and mixed by the extruder, ozone is introduced for oxidation reaction in the melting section and / or homogenization section, and finally, it is extruded through the die of the extruder and cooled and pelletized to obtain a modified PE / PP alloy. Carbonyl groups are introduced into the PE / PP blend based on the principle of free radical reaction, which can quickly and efficiently improve the interfacial compatibility of PE / PP and obtain a PE / PP alloy with excellent properties. The method of the present invention is fast, efficient and environmentally friendly, can realize continuous and large-scale production, and can replace expensive compatibilizers in the future and be applied to the recycling of waste polyethylene and waste polypropylene mixtures.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a method for improving the compatibility of PE / PP blends based on ozone and the obtained product. Background Art

[0002] Polyolefins, including polyethylene (PE) and polypropylene (PP), are widely used in the fields of food, medical and automotive parts due to their low price and easy processing. According to the literature reports, since the 1950s, the total production of PE and PP resins has accounted for about 57% of the global non-fiber plastic production, and PE and PP are mainly used in the packaging industry with a short service life. These two main reasons have led to the rapid generation of a large amount of waste PE and waste PP. In addition, due to their similar physical and chemical properties, it is difficult to separate the two by the traditional floating and sinking method in industry. The performance of PE / PP blends depends on the interfacial compatibility between the two. Although the interfacial compatibility of PE / PP blends can be improved by adding a suitable compatibilizer, the expensive compatibilizer will increase the recycling cost. Therefore, there is an urgent need for an economical, environmentally friendly, rapid and efficient method to improve the interfacial compatibility of PE / PP blends.

[0003] At present, the interfacial compatibility of PE / PP alloy can be improved by increasing the surface polarity of PE or PP, and the method of increasing the surface polarity of PE or PP can be achieved by introducing polar groups into the molecular chain. Currently, the main methods for introducing functional groups into the PE or PP molecular chain include two categories: First, during the synthesis of PE or PP, directly catalyze the polymerization of ethylene or propylene monomers with polar gases to generate PE or PP containing polar functional groups, such as catalytic synthesis; Second, perform polar modification on PE or PP resin, such as chemical reagent treatment and radiation treatment, etc. The first method usually requires preparation under high temperature and high pressure conditions, has high requirements for reaction equipment, and by-products are easily generated during the preparation process. The second method has a simple treatment process and is relatively easy to meet the preparation conditions, but it is often limited to the surface treatment of PE or PP resin. Chinese Patent CN1048770541A, "A Hydroxyl-Terminated Functionalized Hyperbranched Polyethylene and Its Preparation Method", uses ethylene acenaphthene (α-diimine) nickel as the main catalyst, alkyl aluminum as the co-catalyst, and diethyl zinc as the chain transfer catalyst to catalyze the homopolymerization of ethylene monomers, and prepares hydroxyl-terminated hyperbranched polyethylene through coordination chain transfer polymerization. However, this catalytic synthesis method is mainly aimed at introducing polar groups during the synthesis process of polyethylene resin, and this method is difficult to apply to the modification of polyethylene resin. Darvish et al. used plasma to treat biaxially oriented stretched PP, and the generation of different types of oxygen-containing functional groups and nitrogen-containing functional groups in the PP molecular chain improved the surface polarity of PP (Darvish F, Sarkari N M, Khani M, et al. Direct plasma treatment approach based on non-thermal gliding arc for surface modification of biaxially-oriented polypropylene with post-exposure hydrophilicity improvement and minus aging effects[J]. Applied Surface Science, 2020(509), 144815). However, this method requires expensive equipment and is only limited to the surface modification of PP, and it is impossible to achieve large-scale industrial production. Therefore, it is an important task in this technical field to propose a method that can rapidly scale up production, has a simple process flow, and an environmentally friendly reaction process to improve the interfacial compatibility of PE / PP alloy. Summary of the Invention

[0004] To overcome the above disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide a method for effectively improving the compatibility of polyethylene / polypropylene (PE / PP) blends. The present invention provides a method for improving the compatibility of PE / PP blends based on ozone, and the performance of the PE / PP blends after ozone treatment is excellent.

[0005] The present invention is suitable for large-scale production, has a simple process flow, and the reaction process is controllable and environmentally friendly.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] A method for improving the compatibility of PE / PP blends based on ozone, comprising the following steps:

[0008] (1) By mass, polyethylene resin and polypropylene resin are stirred evenly in a high-speed mixer to obtain a PE / PP mixture; the mass of the polyethylene resin is 1 to 100 parts, and the mass of the polypropylene resin is 1 to 100 parts;

[0009] (2) Set the temperature of the extruder and turn on the ozone generator; there are inlet and outlet holes for ozone input and discharge on the barrel of the extruder, and the inlet and outlet holes are arranged in the melting section and / or the homogenization section; ozone is introduced at the inlet and outlet holes and discharged after reacting with PE / PP; the temperature of the extruder at the ozone inlet and outlet holes is 160°C to 300°C;

[0010] (3) Add the PE / PP mixture of step (1) into the hopper of the extruder;

[0011] (4) After the extruder reaches the set temperature, turn on the extruder, and the PE / PP mixture is melted and mixed by the extruder. Ozone is introduced into the melting section and / or the homogenization section for oxidation reaction, and finally extruded through the die of the extruder and cooled and pelletized.

[0012] Preferably, the polyethylene resin in step (1) is at least one of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or metallocene polyethylene (m-PE). More preferably, it is LDPE.

[0013] Preferably, the polypropylene resin in step (1) is at least one of homopolypropylene, block copolymerized polypropylene, or random copolymerized polypropylene. More preferably, it is homopolypropylene.

[0014] Preferably, the ozone in step (2) is prepared by an ozone generator, and the gas source of the ozone generator is at least one of dry air or dry oxygen; the concentration of the ozone gas is 10 g·m -3 ~16 g·m -3, the flow rate of the ozone gas is 10 L·min -1 ~16 L·min -1 .

[0015] More preferably, the gas source of the ozone generator is dry air, and the concentration of the ozone gas is 10 g·m -3 , the flow rate of the ozone gas is 16 L·min -1 .

[0016] Preferably, the extruder described in step (3) is a twin-screw extruder, and the length-diameter ratio is preferably 40∶1.

[0017] Preferably, the temperature of the extruder barrel described in step (4) is set as follows: the feeding section is 100°C, the melting section is 160°C, and the temperature range of the homogenizing section is 160°C~300°C.

[0018] Preferably, the feeding speed of the extruder described in step (4) is 20 rpm~90 rpm, and more preferably 50 rpm.

[0019] Preferably, the main machine speed of the extruder described in step (4) is 50 rpm~150 rpm, and more preferably 100 rpm.

[0020] The present invention provides a modified PE / PP alloy prepared by the above method.

[0021] The present invention uses ozone-functionalized molten PE / PP alloy to prepare a PE / PP alloy with excellent properties, and this reaction occurs during the extrusion process of a twin-screw extruder. There are inlet and outlet holes for ozone to enter and exit on the barrel of the extruder. Ozone is prepared by an ozone generator. The PE / PP mixture is added at the feeding port of the extruder, melted and mixed by the extruder, and undergoes an oxidation reaction with ozone at the inlet and outlet holes, and then is extruded through the die of the extruder to prepare a PE / PP alloy with excellent properties, that is, the mechanical properties of the PE / PP alloy are improved after ozone functionalization.

[0022] During the extrusion process of the PE / PP mixture, ozone is used to react and compatibilize PE / PP, and its principle is as follows:

[0023]

[0024] During the extrusion process of the PE / PP alloy, ozone rapidly undergoes a free radical chain reaction with molten PE and / or molten PP, introducing oxygen atoms and / or oxygen molecules into the molecular chains of PE and / or PP to generate polar oxygen-containing functional groups. Under the interaction of the oxygen-containing functional groups (such as covalent bonds, hydrogen bonds, and van der Waals forces), the molecular chains of PE and PP are entangled, thereby improving the interfacial compatibility between the two phases.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) The present invention uses a twin-screw extruder and adopts ozone to reactively compatibilize the PE / PP alloy. The reaction equipment is simple, the reaction time is short, and continuous large-scale production can be achieved. The obtained PE / PP alloy has excellent properties and can replace expensive compatibilizers and be applied to the recycling of waste polyethylene and waste polypropylene mixtures.

[0027] (2) By controlling factors such as the barrel temperature of the twin-screw extruder, the main machine speed, the feeding speed, the ozone concentration, and the ozone flow rate, the present invention can achieve a controllable reaction.

[0028] (3) The present invention uses ozone, which is environmentally friendly and the reaction process is environmentally friendly. The reaction products are non-toxic and harmless. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the twin-screw extruder, ozone generator, and ozone decomposer used in the embodiments of the present invention.

[0030] Figure 2 It is a graph showing the change of Fourier transform infrared spectroscopy (FTIR) of the modified PE / PP alloy prepared in Examples 1-3 with the barrel temperature of the twin-screw extruder.

[0031] Figure 3 It is a SEM diagram of the modified PE / PP alloy prepared in Example 2 and the pure LDPE / (Homo)PP blend.

[0032] Figure 4 It is a graph showing the change of the impact strength of the modified PE / PP alloy prepared in Examples 1-3 and the pure LDPE / (Homo)PP blend with the barrel temperature of the twin-screw extruder.

[0033] Figure 5 It is a graph showing the change of the impact strength of the modified PE / PP alloy prepared in Example 2 and Examples 4-5 with the ozone concentration.

[0034] Figure 6 It is a graph showing the change of the impact strength of the modified PE / PP alloy prepared in Example 2 and Examples 6-7 with the ozone flow rate.

[0035] Figure 7 It is a graph showing the change of the impact strength of the modified PE / PP alloy prepared in Example 2 and Examples 8-9 with the main machine speed of the twin-screw extruder.

[0036] Figure 8The graph showing the variation of the impact strength of the modified PE / PP alloy prepared in Example 2 and Examples 10 - 11 with the feeding speed of the twin-screw extruder.

[0037] Figure 9 The graph showing the variation of the impact strength of the modified PE / PP alloy prepared in Example 2 and Examples 12 - 15 with the PE content.

[0038] Figure 10 The comparison graph of the impact strength between pure HDPE / (Homo)PP and the modified PE / PP alloy prepared in Example 16.

[0039] Figure 11 The comparison graph of the impact strength between pure LDPE / (Copolymer)PP and the modified PE / PP alloy prepared in Example 17. Detailed implementation manners

[0040] The technical solutions of the present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings. Obviously, the following embodiments are only a part of the embodiments of the present invention, and the embodiments based on the present invention are not limited thereto.

[0041] In the embodiments of the present invention, those not specified in specific conditions are carried out according to conventional conditions or the conditions recommended by the manufacturer. The raw materials, reagents, etc. not specified in the manufacturer are all conventional products that can be obtained through commercial purchase.

[0042] The twin-screw extruder used in the embodiments is a device obtained through structural transformation. Specifically: ozone input and discharge holes are provided on the barrel of the extruder, and the holes are arranged in the homogenization section; ozone is introduced and discharged at the holes. The schematic diagram of the modified device is as Figure 1 shown, where the feeding section is zones 1 and 2, the melting section is zones 3 to 5, the homogenization section is zones 6 to 7, and the die head is zone 8. A polytetrafluoroethylene (PTFE) tube is used to connect the ozone generator and the ozone decomposer to zone 7 of the twin-screw extruder. The structure of the twin-screw extruder body is prior art, and those of ordinary skill in the art should generally know it, so it will not be elaborated here.

[0043] Example 1

[0044] (1) By mass fraction, 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) are respectively weighed, and the above raw materials are added to a high-speed mixer. At room temperature, the rotation speed is 195 r / min, and stirring is carried out for 5 min to obtain a 50 / 50-PE / PP mixture;

[0045] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as Figure 1As shown; connect the ozone generator and the ozone decomposer to Zone 7 of the extruder using PTFE;

[0046] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, and the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0047] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-to-diameter ratio of 40:1, a main machine speed (screw speed) of 100 rpm, a feeding speed of 50 rpm, and the temperature settings are: Zone 1 at 100 °C, Zone 2 at 100 °C, Zone 3 at 160 °C, Zone 4 at 160 °C, Zone 5 at 160 °C, Zone 6 at 160 °C, Zone 7 at 160 °C, Zone 8 at 160 °C;

[0048] (5) After the extruder reaches the set temperature, turn on the extruder for reactive compatibilization, cooling and pelletizing to obtain a 50 / 50-PE / PP alloy.

[0049] Example 2

[0050] (1) By mass, weigh 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) respectively. Add the above raw materials into a high-speed mixer, and at room temperature, with a rotation speed of 195 r / min, stir for 5 min to obtain a 50 / 50-PE / PP mixture;

[0051] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as Figure 1 shown; connect the ozone generator and the ozone decomposer to Zone 7 of the extruder using PTFE;

[0052] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, and the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0053] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-to-diameter ratio of 40:1, a main machine speed (screw speed) of 100 rpm, a feeding speed of 50 rpm, and the temperature settings are: Zone 1 at 100 °C, Zone 2 at 100 °C, Zone 3 at 160 °C, Zone 4 at 160 °C, Zone 5 at 160 °C, Zone 6 at 250 °C, Zone 7 at 250 °C, Zone 8 at 250 °C;

[0054] (5) After the extruder reaches the set temperature, start the extruder for reactive compatibilization, cool and pelletize to obtain a 50 / 50-PE / PP alloy.

[0055] Example 3

[0056] (1) By mass, weigh 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) respectively. Add the above raw materials into a high-speed mixer. At room temperature, with a rotation speed of 195 r / min, stir for 5 min to obtain a 50 / 50-PE / PP mixture;

[0057] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as Figure 1 shown; Connect the ozone generator and the ozone decomposer to the 7th zone of the extruder using PTFE;

[0058] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, and the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0059] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-diameter ratio of 40:1. The main machine speed (screw speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: zone 1 is 100 °C, zone 2 is 100 °C, zone 3 is 160 °C, zone 4 is 160 °C, zone 5 is 160 °C, zone 6 is 300 °C, zone 7 is 300 °C, zone 8 is 300 °C;

[0060] (5) After the extruder reaches the set temperature, start the extruder for reactive compatibilization, cool and pelletize to obtain a 50 / 50-PE / PP alloy.

[0061] Example 4

[0062] (1) By mass, weigh 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) respectively. Add the above raw materials into a high-speed mixer. At room temperature, with a rotation speed of 195 r / min, stir for 5 min to obtain a 50 / 50-PE / PP mixture;

[0063] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as Figure 1 shown; Connect the ozone generator and the ozone decomposer to the 7th zone of the extruder using PTFE;

[0064] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, the concentration of ozone gas is 13 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0065] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-to-diameter ratio of 40:1, the main machine speed (screw speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: zone 1 is 100 °C, zone 2 is 100 °C, zone 3 is 160 °C, zone 4 is 160 °C, zone 5 is 160 °C, zone 6 is 250 °C, zone 7 is 250 °C, and zone 8 is 250 °C;

[0066] (5) After the extruder reaches the set temperature, turn on the extruder for reactive compatibilization, cooling and pelletizing to prepare the 50 / 50-PE / PP alloy.

[0067] Example 5

[0068] (1) By mass, weigh 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) respectively. Add the above raw materials into a high-speed mixer and stir at room temperature at a speed of 195 r / min for 5 min to obtain a 50 / 50-PE / PP mixture;

[0069] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as shown in Figure 1 ; Connect the ozone generator, the ozone decomposer and zone 7 of the extruder with PTFE;

[0070] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, the concentration of ozone gas is 16 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0071] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-to-diameter ratio of 40:1, the main machine speed (screw speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: zone 1 is 100 °C, zone 2 is 100 °C, zone 3 is 160 °C, zone 4 is 160 °C, zone 5 is 160 °C, zone 6 is 250 °C, zone 7 is 250 °C, and zone 8 is 250 °C;

[0072] (5) After the extruder reaches the set temperature, turn on the extruder for reactive compatibilization, cooling and pelletizing to prepare the 50 / 50-PE / PP alloy.

[0073] Example 6

[0074] (1) By mass fraction, 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) were weighed respectively. The above raw materials were added into a high-speed mixer. At room temperature, the rotation speed was 195 r / min and stirred for 5 min to obtain a 50 / 50-PE / PP mixture;

[0075] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as shown in Figure 1 ; PTFE was used to connect the ozone generator and the ozone decomposer to the 7th zone of the extruder;

[0076] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air. The concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 10 L·min -1 ;

[0077] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder. The length-diameter ratio of the twin-screw extruder is 40:1. The main machine rotation speed (screw rotation speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: zone 1 is 100 °C, zone 2 is 100 °C, zone 3 is 160 °C, zone 4 is 160 °C, zone 5 is 160 °C, zone 6 is 250 °C, zone 7 is 250 °C, zone 8 is 250 °C;

[0078] (5) After the extruder reaches the set temperature, turn on the extruder for reactive compatibilization, cooling and pelletizing to prepare a 50 / 50-PE / PP alloy.

[0079] Example 7

[0080] (1) By mass fraction, 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) were weighed respectively. The above raw materials were added into a high-speed mixer. At room temperature, the rotation speed was 195 r / min and stirred for 5 min to obtain a 50 / 50-PE / PP mixture;

[0081] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as shown in Figure 1 ; PTFE was used to connect the ozone generator and the ozone decomposer to the 7th zone of the extruder;

[0082] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air. The concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 13 L·min -1 ;

[0083] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-diameter ratio of 40:1. The main machine speed (screw speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: Zone 1: 100 °C, Zone 2: 100 °C, Zone 3: 160 °C, Zone 4: 160 °C, Zone 5: 160 °C, Zone 6: 250 °C, Zone 7: 250 °C, Zone 8: 250 °C;

[0084] (5) After the extruder reaches the set temperature, start the extruder for reactive compatibilization, followed by cooling and pelletizing to obtain the 50 / 50-PE / PP alloy.

[0085] Example 8

[0086] (1) Weigh 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) by mass. Add the above raw materials into a high-speed mixer and stir at a speed of 195 r / min for 5 min at room temperature to obtain a 50 / 50-PE / PP mixture;

[0087] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as shown in Figure 1 ; Connect the ozone generator and the ozone decomposer to Zone 7 of the extruder using PTFE;

[0088] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0089] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-diameter ratio of 40:1. The main machine speed (screw speed) is 50 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: Zone 1: 100 °C, Zone 2: 100 °C, Zone 3: 160 °C, Zone 4: 160 °C, Zone 5: 160 °C, Zone 6: 250 °C, Zone 7: 250 °C, Zone 8: 250 °C;

[0090] (5) After the extruder reaches the set temperature, start the extruder for reactive compatibilization, followed by cooling and pelletizing to obtain the 50 / 50-PE / PP alloy.

[0091] Example 9

[0092] (1) By weight, 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) were weighed respectively. The above raw materials were added to a high-speed mixer. At room temperature, the rotation speed was 195 r / min, and stirred for 5 min to obtain a 50 / 50-PE / PP mixture;

[0093] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as Figure 1 shown; PTFE was used to connect the ozone generator and the ozone decomposer to the 7th zone of the extruder;

[0094] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, and the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0095] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder. The length-diameter ratio of the twin-screw extruder is 40∶1, the main machine speed (screw speed) is 150 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: zone 1 is 100 °C, zone 2 is 100 °C, zone 3 is 160 °C, zone 4 is 160 °C, zone 5 is 160 °C, zone 6 is 250 °C, zone 7 is 250 °C, zone 8 is 250 °C;

[0096] (5) After the extruder reaches the set temperature, turn on the extruder for reactive compatibilization, cooling and pelletizing to prepare a 50 / 50-PE / PP alloy.

[0097] Example 10

[0098] (1) By weight, 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) were weighed respectively. The above raw materials were added to a high-speed mixer. At room temperature, the rotation speed was 195 r / min, and stirred for 5 min to obtain a 50 / 50-PE / PP mixture;

[0099] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as Figure 1 shown; PTFE was used to connect the ozone generator and the ozone decomposer to the 7th zone of the extruder;

[0100] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, and the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0101] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-diameter ratio of 40:1. The main machine speed (screw speed) is 100 rpm, the feeding speed is 20 rpm, and the temperature settings are as follows: Zone 1: 100 °C, Zone 2: 100 °C, Zone 3: 160 °C, Zone 4: 160 °C, Zone 5: 160 °C, Zone 6: 250 °C, Zone 7: 250 °C, Zone 8: 250 °C;

[0102] (5) After the extruder reaches the set temperature, start the extruder for reactive compatibilization, followed by cooling and pelletizing to obtain the 50 / 50-PE / PP alloy.

[0103] Example 11

[0104] (1) By mass, weigh 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of homopolypropylene (Homo PP-571P) respectively. Add the above raw materials into a high-speed mixer and stir at a speed of 195 r / min for 5 min at room temperature to obtain a 50 / 50-PE / PP mixture;

[0105] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as Figure 1 shown; Connect the ozone generator and the ozone decomposer to Zone 7 of the extruder using PTFE;

[0106] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0107] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-diameter ratio of 40:1. The main machine speed (screw speed) is 100 rpm, the feeding speed is 90 rpm, and the temperature settings are as follows: Zone 1: 100 °C, Zone 2: 100 °C, Zone 3: 160 °C, Zone 4: 160 °C, Zone 5: 160 °C, Zone 6: 250 °C, Zone 7: 250 °C, Zone 8: 250 °C;

[0108] (5) After the extruder reaches the set temperature, start the extruder for reactive compatibilization, followed by cooling and pelletizing to obtain the 50 / 50-PE / PP alloy.

[0109] The component ratios and process parameter settings of Examples 1 to 11 are shown in Table 1.

[0110] Table 1 Component Ratio Table of Examples 1 - 11

[0111]

[0112] Example 12

[0113] (1) By mass, 90 parts of low-density polyethylene (LDPE-2426K) and 10 parts of homopolypropylene (Homo PP-571P) were weighed respectively. The above raw materials were added into a high-speed mixer. At room temperature, the rotation speed was 195 r / min, and stirred for 5 min to obtain a 90 / 10-PE / PP mixture;

[0114] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as shown in Figure 1 ; Connect the ozone generator and the ozone decomposer to the 7th zone of the extruder with PTFE;

[0115] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0116] (4) Add the 90 / 10-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-diameter ratio of 40:1. The main machine rotation speed (screw rotation speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: zone 1 is 100 °C, zone 2 is 100 °C, zone 3 is 160 °C, zone 4 is 160 °C, zone 5 is 160 °C, zone 6 is 250 °C, zone 7 is 250 °C, zone 8 is 250 °C;

[0117] (5) After the extruder reaches the set temperature, turn on the extruder for reactive compatibilization, cooling and pelletizing to prepare a 90 / 10-PE / PP alloy.

[0118] Example 13

[0119] (1) By mass, 70 parts of low-density polyethylene (LDPE-2426K) and 30 parts of homopolypropylene (Homo PP-571P) were weighed respectively. The above raw materials were added into a high-speed mixer. At room temperature, the rotation speed was 195 r / min, and stirred for 5 min to obtain a 70 / 30-PE / PP mixture;

[0120] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as shown in Figure 1 ; Connect the ozone generator and the ozone decomposer to the 7th zone of the extruder with PTFE;

[0121] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min-1 ;

[0122] (4) Add the 70 / 30-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-to-diameter ratio of 40:1. The main machine speed (screw speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: zone 1 at 100 °C, zone 2 at 100 °C, zone 3 at 160 °C, zone 4 at 160 °C, zone 5 at 160 °C, zone 6 at 250 °C, zone 7 at 250 °C, and zone 8 at 250 °C;

[0123] (5) After the extruder reaches the set temperature, start the extruder for reactive compatibilization, followed by cooling and pelletizing to obtain the 70 / 30-PE / PP alloy.

[0124] Example 14

[0125] (1) By mass, weigh 30 parts of low-density polyethylene (LDPE-2426K) and 70 parts of homopolypropylene (Homo PP-571P) respectively. Add the above raw materials into a high-speed mixer and stir at room temperature at a speed of 195 r / min for 5 min to obtain a 30 / 70-PE / PP mixture;

[0126] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as shown in Figure 1 ; Connect the ozone generator and the ozone decomposer to zone 7 of the extruder using PTFE;

[0127] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0128] (4) Add the 30 / 70-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-to-diameter ratio of 40:1. The main machine speed (screw speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: zone 1 at 100 °C, zone 2 at 100 °C, zone 3 at 160 °C, zone 4 at 160 °C, zone 5 at 160 °C, zone 6 at 250 °C, zone 7 at 250 °C, and zone 8 at 250 °C;

[0129] (5) After the extruder reaches the set temperature, start the extruder for reactive compatibilization, followed by cooling and pelletizing to obtain the 30 / 70-PE / PP alloy.

[0130] Example 15

[0131] (1) By weight, 10 parts of low-density polyethylene (LDPE-2426K) and 90 parts of homopolypropylene (Homo PP-571P) were weighed respectively. The above raw materials were added to a high-speed mixer. At room temperature, the rotation speed was 195 r / min, and the mixture was stirred for 5 min to obtain a 10 / 90-PE / PP mixture;

[0132] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as shown in Figure 1 ; PTFE was used to connect the ozone generator and the ozone decomposer to the 7th zone of the extruder;

[0133] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0134] (4) Add the 10 / 90-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-diameter ratio of 40:1. The main machine rotation speed (screw rotation speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature is set as follows: zone 1 is 100 °C, zone 2 is 100 °C, zone 3 is 160 °C, zone 4 is 160 °C, zone 5 is 160 °C, zone 6 is 250 °C, zone 7 is 250 °C, zone 8 is 250 °C;

[0135] (5) After the extruder reaches the set temperature, turn on the extruder for reactive compatibilization and cooling pelletization to prepare 10 / 90-PE / PP alloy.

[0136] Example 16

[0137] (1) By weight, 50 parts of high-density polyethylene (HDPE-M80064) and 50 parts of homopolypropylene (Homo PP-571P) were weighed respectively. The above raw materials were added to a high-speed mixer. At room temperature, the rotation speed was 195 r / min, and the mixture was stirred for 5 min to obtain a 50 / 50-PE / PP mixture;

[0138] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as shown in Figure 1 ; PTFE was used to connect the ozone generator and the ozone decomposer to the 7th zone of the extruder;

[0139] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0140] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-to-diameter ratio of 40:1. The main machine speed (screw speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature settings are as follows: Zone 1: 100 °C, Zone 2: 100 °C, Zone 3: 160 °C, Zone 4: 160 °C, Zone 5: 160 °C, Zone 6: 250 °C, Zone 7: 250 °C, Zone 8: 250 °C;

[0141] (5) After the extruder reaches the set temperature, start the extruder for reactive compatibilization, followed by cooling and pelletizing to obtain the 50 / 50-PE / PP alloy.

[0142] Example 17

[0143] (1) Weigh 50 parts of low-density polyethylene (LDPE-2426K) and 50 parts of copolymer polypropylene (Copolymer PP-621P) by mass. Add the above raw materials into a high-speed mixer and stir at a speed of 195 r / min for 5 min at room temperature to obtain a 50 / 50-PE / PP mixture;

[0144] (2) Set the temperature of the extruder. The schematic diagram of the extruder device is as shown in Figure 1 ; Connect the ozone generator and the ozone decomposer to Zone 7 of the extruder using PTFE;

[0145] (3) Turn on the ozone generator and the ozone decomposer. The gas source of the ozone generator is dry air, the concentration of ozone gas is 10 g·m -3 , and the flow rate of ozone gas is 16 L·min -1 ;

[0146] (4) Add the 50 / 50-PE / PP mixture obtained in step (1) into the hopper of the extruder. The extruder is a twin-screw extruder with a length-to-diameter ratio of 40:1. The main machine speed (screw speed) is 100 rpm, the feeding speed is 50 rpm, and the temperature settings are as follows: Zone 1: 100 °C, Zone 2: 100 °C, Zone 3: 160 °C, Zone 4: 160 °C, Zone 5: 160 °C, Zone 6: 250 °C, Zone 7: 250 °C, Zone 8: 250 °C;

[0147] (5) After the extruder reaches the set temperature, start the extruder for reactive compatibilization, followed by cooling and pelletizing to obtain the 50 / 50-PE / PP alloy.

[0148] The component ratios of Examples 12 to 17 are shown in Table 2.

[0149] Table 2 Component Ratio Table of Examples 12 - 17

[0150] PE / PP (parts ratio) PE type PP type Example 12 90 / 10 LDPE Homopolymerization Example 13 70 / 30 LDPE Homopolymerization Example 14 30 / 70 LDPE Homopolymerization Example 15 10 / 90 LDPE Homopolymerization Example 16 50 / 50 HDPE Homopolymerization Example 17 50 / 50 LDPE Copolymerization

[0151] Figure 2 Variation curve of Fourier transform infrared spectroscopy (FTIR) of the modified PE / PP blend alloys prepared in Examples 1 to 3 with the temperature of the barrel of the twin-screw extruder. From Figure 2 It can be seen that through ozone oxidation, all examples have successfully introduced oxygen-containing functional groups into the PE / PP blend alloy. This indicates that the preparation method of the present invention can quickly and effectively introduce oxygen-containing functional groups into the PE / PP blend. Specifically, the oxygen-containing functional group is the carbonyl group (C=O) at 1720 cm -1 . The introduction of oxygen-containing functional groups will help improve the polarity of PE and PP, and further promote the interfacial compatibility between PE and PP. In addition, as the temperature of the extruder barrel increases, the intensity of the carbonyl peak first increases and then decreases, which indicates that appropriately increasing the temperature can promote the reaction. From Figure 2 It can also be seen that the carbonyl peak of Example 3 is lower than that of Example 2. This is mainly because too high a temperature will cause the molecular chains of PE to crosslink or form a network structure, which is prone to generate ether bonds; in addition, the molecular chains of PP are prone to breakage, and gaseous molecules will be generated at the same time, resulting in a decrease in oxygen-containing functional groups.

[0152] Figure 3 SEM images of the modified PE / PP blend alloy prepared in Example 2 and the pure LDPE / (Homo)PP blend. From Figure 3 It can be seen that there are many pores in the pure LDPE / (Homo)PP blend, and the two-phase interface is obvious. After ozone treatment, there is no obvious interface between the two phases of PE and PP, and the compatibility between PE and PP is significantly improved. This indicates that the preparation method of the present invention can quickly and efficiently improve the interfacial compatibility of the PE / PP blend alloy.

[0153] Figure 4 Variation curve of the impact strength of the modified PE / PP blend alloys prepared in Examples 1 to 3 and the pure LDPE / (Homo)PP blend with the temperature of the barrel of the twin-screw extruder. The impact strength can directly reflect the interfacial compatibility degree between PE and PP. Generally speaking, the higher the impact strength, the better the interfacial compatibility. From Figure 4 It can be seen that the impact strengths of the modified PE / PP blend alloys in the examples are all higher than those of the pure LDPE / (Homo)PP blend. Specifically, the impact strength: Example 2 > Example 3 > Example 1 > pure LDPE / (Homo)PP, which indicates that the preparation method of the present invention can appropriately improve the interfacial compatibility of the PE / PP blend alloy. In addition, by appropriately increasing the reaction temperature, the interfacial compatibility of the PE / PP blend alloy increases, which is mainly caused by the generation of more oxygen-containing functional groups at a higher reaction temperature. From Figure 4It can also be seen that the impact strength peak of Example 3 is lower than that of Example 2. This is because although a higher reaction temperature is conducive to the rapid and efficient introduction of oxygen-containing functional groups into the molecular chains of PE and PP, it will simultaneously cause the formation of crosslinks or network structures between the PE molecular chains themselves, and the β-chain breakage of the PP molecular chains. Therefore, appropriately increasing the temperature can ensure the introduction of a certain amount of oxygen-containing functional groups while ensuring that fewer crosslinks and network structures are formed in the PE molecular chains and less molecular chain breakage occurs in PP.

[0154] Figure 5 Figure showing the variation of the impact strength of the modified PE / PP blend alloys prepared in Example 2 and Examples 4 - 5 with ozone concentration. From Figure 5 It can be seen that as the ozone concentration increases, the impact strength of the modified PE / PP blend alloys in the examples gradually increases. Specifically, Example 5 > Example 4 > Example 2. This shows that appropriately increasing the ozone concentration is beneficial to improving the interfacial compatibility of the PE / PP blend alloys.

[0155] Figure 6 Figure showing the variation of the impact strength of the modified PE / PP blend alloys prepared in Example 2 and Examples 6 - 7 with ozone flow rate. From Figure 6 It can be seen that as the ozone flow rate increases, the impact strength of the modified PE / PP blend alloys in the examples gradually increases. Specifically, Example 2 > Example 7 > Example 6. This shows that appropriately increasing the ozone flow rate is beneficial to improving the interfacial compatibility of the PE / PP blend alloys.

[0156] Figure 7 Figure showing the variation of the impact strength of the modified PE / PP blend alloys prepared in Example 2 and Examples 8 - 9 with the main screw speed of the twin-screw extruder. From Figure 7 It can be seen that as the main screw speed decreases, the impact strength of the modified PE / PP blend alloys in the examples gradually increases. Specifically, Example 8 > Example 2 > Example 9. This shows that appropriately reducing the main screw speed will prolong the reaction time of ozone with the melt, which is beneficial to improving the interfacial compatibility of the PE / PP blend alloys.

[0157] Figure 8 Figure showing the variation of the impact strength of the modified PE / PP blend alloys prepared in Example 2 and Examples 10 - 11 with the feeding speed of the twin-screw extruder. From Figure 8 It can be seen that as the feeding speed decreases, the impact strength of the modified PE / PP blend alloys in the examples gradually increases. Specifically, Example 10 > Example 2 > Example 11. This shows that reducing the feeding speed will prolong the reaction time of ozone with the melt, which is beneficial to improving the interfacial compatibility of the PE / PP blend alloys.

[0158] Figure 9Figure showing the variation of the impact strength of the modified PE / PP alloy blends prepared in Example 2 and Examples 12 - 15 with the PE content. From Figure 9 it can be seen that as the PE content increases, the impact strength of the PE / PP alloy blends in the examples gradually increases. Specifically, Example 12 > Example 13 > Example 2 > Example 14 > Example 15. This is mainly determined by the physical properties of the PE and PP matrices. PE is a ductile material while PP is a brittle material. Increasing the PE content in the modified PE / PP blend is beneficial for increasing the impact strength of the mixture. In addition, compared to PP, ozone is more likely to introduce more oxygen-containing functional groups in PE. Therefore, when the PE content in the modified PE / PP blend is relatively large, the relatively large number of oxygen-containing functional groups in PE is beneficial for improving the interfacial compatibility.

[0159] Figure 10 Figure comparing the impact strength of pure HDPE / (Homo)PP and the modified PE / PP alloy blend prepared in Example 16. From Figure 10 it can be seen that compared to pure HDPE / (Homo)PP, the impact strength of the ozone-functionalized PE / PP alloy blend has been significantly improved. Figure 11 Figure comparing the impact strength of pure LDPE / (Copolymer)PP and the modified PE / PP alloy blend prepared in Example 17. From Figure 11 it can be seen that compared to pure LDPE / (Copolymer)PP, the impact strength of the ozone-functionalized PE / PP alloy blend has been significantly improved. This is mainly because the introduction of oxygen-containing functional groups is beneficial for enhancing the entanglement between the PE and PP molecular chains, promoting the interfacial compatibility of PE / PP, and thus improving the mechanical properties of the PE / PP alloy.

[0160] Through Figures 2 to 11 and related descriptions, it can be proven that using the preparation method of the present invention can rapidly prepare a PE / PP alloy blend and improve its interfacial compatibility. This method can be used for the recycling of waste polyethylene and waste polypropylene.

[0161] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for improving the compatibility of PE / PP blends based on ozone, characterized in that, It includes the following steps: (1) Add polyethylene resin and polypropylene resin into a high-speed mixer in a mass ratio of 90 / 10 and stir evenly to obtain a PE / PP mixture; (2) Set the temperature of the extruder and turn on the ozone generator; there are ozone inlet and outlet holes on the barrel of the extruder, and the inlet and outlet holes are arranged in the melting section and / or the homogenization section; the temperature of the homogenization section is 250 °C; ozone is introduced through the inlet and outlet holes and discharged after reacting with PE / PP; the concentration of ozone gas is 10 g·m -3 ~16 g·m -3 , and the flow rate of ozone gas is 10 L·min -1 ~16 L·min -1 ; (3) Add the PE / PP mixture in step (1) into the hopper of an extruder; (4) After the extruder reaches the set temperature, start the extruder. The feeding speed of the extruder is 20 rpm to 90 rpm, and the main machine speed of the extruder is 50 rpm to 150 rpm. The PE / PP mixture is melted and mixed by the extruder, and ozone is introduced into the melting section and / or homogenization section for oxidation reaction, and finally extruded through the die of the extruder and cooled and pelletized.

2. The method for improving the compatibility of PE / PP alloy based on ozone according to claim 1, wherein The polyethylene resin in step (1) is at least one of high-density polyethylene, low-density polyethylene, linear low-density polyethylene or metallocene polyethylene.

3. The method for improving the compatibility of PE / PP alloy based on ozone according to claim 1, characterized in that The polypropylene resin in step (1) is at least one of homopolypropylene, block copolymerized polypropylene or random copolymerized polypropylene.

4. The method for improving the compatibility of PE / PP alloy based on ozone according to claim 1, characterized in that The ozone in step (2) is prepared by an ozone generator, and the gas source of the ozone generator is at least one of dry air or dry oxygen.

5. The method for improving the compatibility of PE / PP alloy based on ozone according to claim 1, wherein The extruder in step (3) is a twin-screw extruder with a length-diameter ratio of 40:

1.

6. The method for improving the compatibility of PE / PP alloy based on ozone according to claim 1, characterized in that, The barrel temperature of the extruder in step (4) is set as follows: the feeding section is 100 °C, and the melting section is 160 °C.

7. A modified PE / PP alloy prepared by the method according to any one of claims 1-6.

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