Preparation method of maleic anhydride grafted polyethylene

Abstract

The invention provides maleic anhydride grafted polyethylene and a preparation method thereof, and relates to the technical field of high polymer materials. The maleic anhydride grafted polyethylene is prepared from the following raw materials in parts by weight: 100 parts of polyethylene resin, 0.1 to 2 parts of maleic anhydride, 0.01 to 0.5 part of a free radical initiator, 0.01 to 0.5 part of an antioxidant, 0.1 to 2 parts of a third monomer, 0.01 to 0.5 part of a stabilizer and 0.01 to 0.5 part of a crosslinking modifier, in the preparation process of the maleic anhydride grafted polyethylene, the stabilizer and the cross-linking modifier are added, so that the cross-linking reaction is prevented, the stability of the grafting reaction is controlled, the maleic anhydride grafted polyethylene with high grafting rate and good flow processability is obtained, and the practical application of the compatilizer in different scenes is met.

Description

Technical Field

[0001] This application relates to the field of polymer materials, and more particularly to a method for preparing maleic anhydride-grafted polyethylene. Background Technology

[0002] Maleic anhydride grafted modified polyethylene is a process in which maleic anhydride molecules are grafted onto the polyethylene molecular chain through a chemical reaction. This process endows the polyethylene with the reactivity and strong polarity of maleic anhydride molecules. After modification, maleic anhydride can improve the interfacial affinity between the polyethylene matrix and inorganic materials such as metal powder, glass fiber, wood flour, mineral powder, and starch, thereby enhancing the strength of the composite material. It is often used as a compatibilizer for polyethylene materials.

[0003] Common methods for grafting polyethylene include solution extraction, melt extrusion, radiation extraction, and solid-state extraction. Melt extrusion is the most frequently used method. It involves thoroughly mixing maleic anhydride, a third monomer, polyethylene, and an initiator in a specific ratio, and then reactively extruding the mixture in an extruder with a screw length-to-diameter ratio (L / D) greater than 50. Melt extrusion is a chemical reaction process in which the following reactions occur simultaneously: Reaction 1: Maleic anhydride is attached to polyethylene, and then a third monomer alternates with maleic anhydride to form blocks.

[0004] Reaction 2: Maleic anhydride reacts with a third monomer to form a block, which is then grafted onto polyethylene.

[0005] Reaction 3: Maleic anhydride molecules self-polymerize to form maleic anhydride macromolecular chains.

[0006] Reaction 4: Polyethylene molecules self-polymerize to form cross-linked macromolecular chains.

[0007] Reactions 1 and 2 are favorable for the melt grafting process, while reactions 3 and 4 are side reactions. Side reaction 3 causes the product to turn yellow or red, and side reaction 4 reduces the melt flow index and makes processing difficult. Currently, the melt extrusion method for producing maleic anhydride-grafted modified polyethylene suffers from low grafting rates and poor product flowability, limiting its application. Therefore, in the melt extrusion production of maleic anhydride-grafted modified polyethylene, how to improve the monomer grafting rate while controlling crosslinking side reactions to improve processing flowability is an urgent problem to be solved. Summary of the Invention

[0008] The purpose of this application is to address the shortcomings of the prior art by providing a method for preparing maleic anhydride-grafted polyethylene. By adding stabilizers and crosslinking modifiers during the process of maleic anhydride-grafted polyethylene, this application can reduce the occurrence of side reactions in the melt extrusion production of maleic anhydride-grafted modified polyethylene, improve the grafting rate, and enhance processing fluidity.

[0009] To achieve the above objectives, the technical solution adopted in this application is as follows: According to one aspect of this application, a maleic anhydride-grafted polyethylene is provided, comprising the following parts by weight of raw materials: 100 parts polyethylene resin, 0.1-2 parts maleic anhydride, 0.01-0.5 parts free radical initiator, 0.01-0.5 parts antioxidant, 0.1-2 parts third monomer, 0.01-0.5 parts stabilizer, and 0.01-0.5 parts crosslinking modifier; The stabilizer is a tin-based stabilizer; the crosslinking modifier is selected from any one or more of trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, and triallyl isocyanurate.

[0010] Furthermore, the stabilizer is preferably one or more of dimethyltin, dioctyltin, tetraphenyltin, dibutyltin dilaurate, tin tributyl phosphate, tanshinone tri(N-ethyl,N-hexyl)oxide, and tin trioctanoate.

[0011] At high temperatures, the decomposition rate of peroxide initiators is very fast, leading to cross-linking side reactions. Therefore, this application adds a tin-based stabilizer during the maleic anhydride grafting polyethylene reaction. The stabilizer can catalyze the reverse reaction of the decomposition reaction, thereby slowing down the decomposition rate of peroxides and preventing the occurrence of cross-linking side reactions due to excessively rapid decomposition of peroxides.

[0012] Further, the amount of stabilizer in 100 parts of polyethylene resin is 0.01-0.5 parts, for example, it can be 0.01 parts, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.5 parts or any range thereto; preferably 0.1-0.15 parts.

[0013] This application adds a crosslinking modifier during the grafting of maleic anhydride onto polyethylene. In the presence of free radicals, due to the steric hindrance effect, it tends to link small molecules such as MAH. Therefore, during the maleic anhydride grafting reaction, it can react rapidly with polymer free radicals, avoiding the self-polymerization of polymer free radicals to form a crosslinking network, and thus improving the grafting rate of MAH.

[0014] Further, the amount of the crosslinking modifier in 100 parts of polyethylene resin is 0.01-0.5 parts, for example, it can be 0.01 parts, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.5 parts or any range thereto; preferably 0.1-0.15 parts.

[0015] Furthermore, the weight ratio of the stabilizer to the crosslinking modifier is 1:(1-1.5).

[0016] Furthermore, the polyethylene resin is selected from any one or a combination of high-density polyethylene resin (HDPE), low-density polyethylene resin (LDPE), linear low-density polyethylene resin (LLDPE), and metallocene polyethylene resin.

[0017] Further, the third monomer is a compound with unsaturated double bonds other than maleic anhydride, preferably a styrene-containing compound, such as styrene, divinylbenzene, p-(3-butenyl)styrene, more preferably styrene; the amount of styrene in 100 parts of polyethylene resin is 0.1-2 parts, for example, it can be 0.1 parts, 0.11 parts, 0.12 parts, 0.13 parts, 0.14 parts, 0.15 parts, 0.16 parts, 0.17 parts, 0.18 parts, 0.19 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 2 parts or any range between therewith; preferably 0.6-1 part.

[0018] Furthermore, the free radical initiator is selected from peroxide initiators, preferably any one or a combination of DCP, TBEC, BIBP, TAEC, and DTBP.

[0019] Furthermore, the amount of free radical initiator can be adjusted according to the amount of reactants, reaction temperature, time, and other conditions. Generally, the amount of free radical initiator is greater than 0.01% of the reactants. Preferably, 0.01-0.5 parts of free radical initiator are added to 100 parts of polyethylene resin, for example, 0.01 parts, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.5 parts, or any range between them.

[0020] Furthermore, the antioxidant is selected from anti-thermal oxidative aging agents, preferably any one or a combination of antioxidant 1010, antioxidant 168, antioxidant 1076, antioxidant 1098, antioxidant 626, and antioxidant 264.

[0021] Furthermore, the amount of antioxidant can be adjusted according to the amount of reactants, reaction temperature, time, and other conditions. Generally, the amount of antioxidant is greater than 0.01% of the weight of the reactants. Preferably, 0.01-0.5 parts of free radical initiator are added to 100 parts of polyethylene resin, for example, 0.01 parts, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.5 parts, or any range between them.

[0022] According to another aspect of this application, a method for preparing maleic anhydride-grafted polyethylene is provided, comprising the following steps: (1) Add maleic anhydride, third monomer, free radical initiator, crosslinking modifier, stabilizer and antioxidant to polyethylene resin and mix thoroughly to obtain a mixture; (2) The mixture obtained in step (1) is fed into an extruder for melt extrusion; (3) Cool the material extruded in step (2), cut it into pellets, and dry it to obtain the final product.

[0023] Furthermore, in step (2), the extruder temperature range is 80-190℃, the main machine speed is 100-300rpm, and the feeding speed is 10-33.0Hz.

[0024] Preferably, the temperatures of each section of the extruder are: 80℃, 140℃, 150℃, 160℃, 170℃, 185℃, 190℃, 190℃, 190℃, 190℃, 180℃, with the screen changer temperature control at 180℃ and the die head temperature control at 180℃.

[0025] Compared with the prior art, this application has the following beneficial effects: 1. The method for preparing maleic anhydride-grafted polyethylene provided in this application effectively controls the decomposition rate of peroxide free radicals by adding a crosslinking modifier, avoiding excessively rapid peroxide free radical initiation that could lead to crosslinking or gelation; and ensures the stability of free radicals and the thermal stability of the molecular chains by adding a stabilizer, thereby reducing the degree of degradation of the system. By adding stabilizers and crosslinking modifiers, the chemical grafting reaction process is prevented from occurring and the stability of the grafting reaction is controlled from both preventive and control perspectives.

[0026] 2. The maleic anhydride-grafted polyethylene provided in this application has a high grafting rate and good flowability, which meets the practical application requirements of compatibilizers in different scenarios. Detailed Implementation

[0027] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of this application, but do not limit this application in any way. The following content is merely an exemplary description of the scope of protection claimed in this application, and those skilled in the art can make various changes and modifications to the invention based on the disclosed content, which should also fall within the scope of protection claimed in this application.

[0028] Unless otherwise specified, all chemical reagents used in the embodiments of this application were obtained through conventional commercial channels. In the specific embodiments below, HDPE resin 8008 was purchased from Dushanzi Petrochemical Company; the stabilizer dibutyltin dilaurate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; the crosslinking modifier TMPTMA was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; and the antioxidants 1010 and 168 were purchased from Beijing Jiyi Holding Group Co., Ltd. It should be understood that the specific materials given above do not constitute a limitation on this application. Other materials provided in this application can be substituted to achieve the technical effects of this application, but due to the large number of materials, they are not described in detail here.

[0029] The amount of maleic anhydride grafted polyethylene in this application can be adjusted according to actual needs, for example, it can be 0.1% of the weight of polyethylene resin, or 1%, 10% of the weight of polyethylene resin, etc. The type and amount of the third monomer can also be adjusted according to actual needs. In the following specific embodiments, this application uses 100 parts of HDPE resin, 0.1-2 parts of maleic anhydride, and 0.1-2 parts of the third monomer styrene as an example to produce maleic anhydride grafted polyethylene, which does not constitute a limitation of this application.

[0030] The present application will be further described below by way of specific embodiments.

[0031] Example 1 This embodiment provides a method for preparing maleic anhydride-grafted polyethylene, comprising the following steps: (1) Add 1.5 parts maleic anhydride and 1 part styrene to 100 parts HDPE resin, then add 1 part styrene, 0.15 parts free radical initiator DCP, 0.1 parts crosslinking modifier, 0.1 parts stabilizer and 0.3 parts antioxidant, and mix thoroughly to obtain a mixture; (2) The mixture obtained in step (1) is fed into the extruder. The extruder temperature is set to 80℃, 140℃, 150℃, 160℃, 170℃, 185℃, 190℃, 190℃, 190℃, 190℃, 180℃, the screen changer temperature control is 180℃, the die head temperature control is 180℃, the main machine speed is 300rpm, and the feed speed is 33rpm. The melt reaction extrusion is carried out. (3) The material molten and extruded in step (2) is cooled with cooling water, granulated, and dried to obtain the final product.

[0032] Example 2 The difference from Example 1 is that the amount of stabilizer used is 0.15 parts.

[0033] Example 3 The difference from Example 1 is that the amount of maleic anhydride is 2 parts, the amount of styrene is 2 parts, the amount of crosslinking modifier is 0.5 parts, and the amount of stabilizer is 0.5 parts.

[0034] Example 4 The difference from Example 1 is that the amount of maleic anhydride is 0.1 parts, the amount of styrene is 0.1 parts, the amount of crosslinking modifier is 0.01 parts, and the amount of stabilizer is 0.01 parts.

[0035] Comparative Example 1 The difference from Example 1 is that no crosslinking modifier and stabilizer were added.

[0036] Comparative Example 2 The difference from Example 1 is that no crosslinking modifier was added.

[0037] Comparative Example 3 The difference from Example 1 is that no stabilizer was added.

[0038] Comparative Example 4 The difference from Example 1 is that the amount of crosslinking modifier used is 0.8 parts.

[0039] Comparative Example 5 The difference from Example 1 is that the amount of stabilizer used is 0.8 parts.

[0040] Test case Using the maleic anhydride-grafted polyethylene products obtained in the examples and comparative examples as samples, their melt flow index was tested according to GB / T 3682, their grafting rate was tested using infrared spectroscopy, and their tensile strength and elongation at break were tested according to GB / T 1040. The test results are shown in Table 1 below: Table 1

[0041] As shown in the table, compared to Example 1, Comparative Example 1, which did not add crosslinking modifiers and stabilizers, showed a significant decrease in the grafting rate of the maleic anhydride-grafted polyethylene, as well as a reduction in tensile strength and elongation at break. Similarly, Comparative Example 2, which did not add crosslinking modifiers, and Example 3, which did not add stabilizers, also showed a significant decrease in the grafting rate of the maleic anhydride-grafted polyethylene, along with reductions in tensile strength and elongation at break. This demonstrates that under the same conditions, the simultaneous addition of crosslinking modifiers and stabilizers helps reduce side reactions during melt extrusion, improves the grafting rate of the product, and enhances tensile properties. In Comparative Examples 4 and 5, the excessive addition of crosslinking modifiers or stabilizers also resulted in a decrease in the grafting rate of the products; although the tensile strength was high, the elongation at break decreased significantly.

[0042] The melt flow index (MFI) represents the quality of processing performance. We have painstakingly supplemented the MFI analysis of each example and comparative example. During polyethylene grafting, the MFI is affected by the grafting rate and the crosslinking reaction process. Generally, an increased grafting rate leads to a lower MFI, and an increased degree of crosslinking also leads to a lower MFI. The crosslinking process has a greater impact on the MFI than the grafting process. Comparing Comparative Example 4 with Example 1, the excessive crosslinking agent content did not increase the MAH grafting rate; instead, it led to a lower MFI. This indicates that the grafting reaction, influenced by the amount of MAH, was complete during the reaction. The increased crosslinking agent caused the crosslinking reaction, resulting in a lower MFI. Tensile strength slightly increased, while elongation decreased.

[0043] In processing applications, a low melt index results in poor fluidity, increasing processing difficulty and energy consumption. Conversely, a high melt index leads to low zero-shear viscosity, relatively small molecular weight, and lower physical properties. Therefore, in practical applications, it is necessary to consider both processing performance and physical properties.

[0044] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, this application is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope of this application should be within the protection scope of this application.

Claims

1. A maleic anhydride-grafted polyethylene, characterized in that, Contains the following ingredients by weight: 100 parts polyethylene resin, 0.1-2 parts maleic anhydride, 0.01-0.5 parts free radical initiator, 0.01-0.5 parts antioxidant, 0.1-2 parts third monomer, 0.01-0.5 parts stabilizer, and 0.01-0.5 parts crosslinking modifier; The stabilizer is a tin-based stabilizer; the crosslinking modifier is selected from any one or more of trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, and triallyl isocyanurate.

2. The maleic anhydride-grafted polyethylene according to claim 1, characterized in that, The stabilizer is any one or a combination of dimethyltin, dioctyltin, tetraphenyltin, dibutyltin dilaurate, tin tributyl phosphate, tanshinone tri(N-ethyl,N-hexyl)oxide, and tin trioctanoate.

3. The maleic anhydride-grafted polyethylene according to claim 1, characterized in that, The weight ratio of the stabilizer to the crosslinking modifier is 1:(1-1.5).

4. The maleic anhydride-grafted polyethylene according to claim 1, characterized in that, The polyethylene resin is selected from any one or a combination of high-density polyethylene resin (HDPE), low-density polyethylene resin (LDPE), linear low-density polyethylene resin (LLDPE), and metallocene polyethylene resin.

5. The maleic anhydride-grafted polyethylene according to claim 1, characterized in that, The free radical initiator is selected from peroxide initiators, preferably any one or a combination of DCP, TBEC, BIBP, TAEC, and DTBP.

6. The maleic anhydride-grafted polyethylene according to claim 1, characterized in that, The antioxidant is selected from anti-thermal oxidative aging agents, preferably any one or a combination of antioxidant 1010, antioxidant 168, antioxidant 1076, antioxidant 1098, antioxidant 626, and antioxidant 264.

7. The maleic anhydride-grafted polyethylene according to claim 1, characterized in that, The third monomer is a compound with unsaturated double bonds other than maleic anhydride.

8. The maleic anhydride-grafted polyethylene according to claim 7, characterized in that, The third monomer is any one or more of styrene, divinylbenzene, and p-(3-butenyl)styrene.

9. The method for preparing maleic anhydride-grafted polyethylene according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Add maleic anhydride, third monomer, free radical initiator, crosslinking modifier, stabilizer and antioxidant to polyethylene resin and mix thoroughly to obtain a mixture; (2) The mixture obtained in step (1) is fed into an extruder for melt extrusion; (3) Cool the material extruded in step (2), cut it into pellets, and dry it to obtain the final product.

10. The preparation method according to claim 9, characterized in that, The extruder temperature range is 80-190℃.

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