A branching agent, its preparation method and application

Abstract

This invention relates to the field of polymer materials technology, and particularly to a branching agent, its preparation method, and its application. This branching agent contains a double bond structure and readily reacts with a branching initiator under high-temperature processing conditions to generate branching agent free radicals. Under high-temperature conditions, hydrogen atoms bonded to tertiary carbon atoms in the EVA backbone are easily lost, generating EVA backbone free radicals. These branching agent free radicals combine with EVA backbone free radicals to form a branched structure. Simultaneously, this branching agent can also connect different EVA molecular chains to form long-chain branched structures, increasing intermolecular entanglement and interaction, thereby reducing the melt index and increasing tensile strength. The branching agent has high branching efficiency, and the degree of branching of EVA can be affected by adjusting the amount of branching agent or the double bond content in the branching agent, thus achieving adjustments to the melt index and tensile strength of the modified EVA, solving the problem of low EVA strength in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a branching agent and its preparation method, as well as the application of the branching agent in the preparation of high-strength EVA (ethylene-vinyl acetate copolymer) materials with long-chain branched structures. Background Technology

[0002] Ethylene-vinyl acetate copolymer (EVA) plays a crucial role in modern industry as an important polymer. It is produced by high-pressure continuous bulk polymerization of ethylene and vinyl acetate monomers under specific temperature and pressure conditions, and can be used in photovoltaic films, wires and cables, and shoe material foaming. High-strength EVA products with high vinyl acetate (VA) content are important raw materials for high-end EVA foam products due to their flexibility, high elasticity, and excellent processing performance. They can be used not only in the production of supercritical foam materials but also in high-grade wire and cable materials, making them highly favored by downstream enterprises, and demand continues to rise. However, because the EVA molecular structure is predominantly linear, although there are some branches, the branch lengths are short, and long branches are very few. High VA content EVA often has relatively low tensile strength and melt strength, making it less suitable for supercritical foaming processes. In various foaming processes, especially supercritical foaming, high polymer strength is required to ensure cell stability. Besides copolymer composition, EVA strength is generally closely related to long-chain branching, molecular weight, and its distribution. Therefore, developing EVA products with higher strength has become an urgent need for the industry and is of great significance for promoting technological upgrading and sustainable development in related industries.

[0003] Currently, there are two main technical approaches to improve the strength of EVA: one is to composite EVA with other materials, such as inorganic fillers and other polymers, through blending or copolymerization. This leverages the synergistic effects between different materials to enhance the overall performance of EVA. However, due to differences in compatibility and performance between different components, as well as processing and cost factors, the application scenarios of such composite materials are often limited. The other approach is to improve the strength of EVA by altering its molecular structure. EVA's molecular structure is predominantly linear, with some branches, but these branches are relatively short, and long branches are very rare. Since the strength of a material is closely related to its molecular structure, long-chain branched structures can increase the entanglement and interaction between molecular chains, thereby improving the material's strength. Therefore, introducing long-chain branched structures is an effective way to improve the strength of EVA.

[0004] Currently, the preparation of high-strength EVA products with long-chain branched structures mainly employs free radical (such as free radical initiators like dicumyl peroxide (DCP)) or radiation crosslinking techniques. Free radical crosslinking utilizes the decomposition of free radical initiators under heating conditions to generate free radicals, initiating a crosslinking reaction in the EVA molecular chains to form a long-chain branched structure. Radiation crosslinking uses high-energy rays (such as gamma rays or electron beams) to irradiate the EVA material, causing the molecular chains to generate free radicals, which then initiate a crosslinking reaction. Both techniques can improve the strength of EVA to some extent, and in most cases, branching agents are not used, making the operation relatively simple. However, crosslinking agents / branching agents are sometimes used to further enhance the strength of EVA products. However, most of the crosslinking agents / branching agents currently used are those invented in the 1980s for rubber, such as triallyl cyanurate (TAC) or triallyl isocyanurate (TIAC). These crosslinking agents / branching agents can promote the crosslinking and branching of EVA molecular chains to a certain extent and improve the strength of the material, but they have low chemical grafting efficiency, resulting in incomplete crosslinking and branching reactions, and the product strength is difficult to reach the expected level.

[0005] In summary, existing technologies for improving the strength of EVA have many problems, and further research and development of new technologies are needed to produce high-strength EVA products with superior performance and wider applications. Summary of the Invention

[0006] To address the problem of low strength of EVA in existing technologies, this invention provides a branching agent, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a branching agent, which is obtained by copolymerizing an epoxy compound containing double bonds with an epoxy compound without double bonds. The epoxy compound containing double bonds includes one of 3,4-epoxy-1-butene, 4,5-epoxy-1-cyclohexene, and 4,5-epoxy-3-methyl-1-cyclohexene; the epoxy compound without double bonds includes one of ethylene oxide, epichlorohydrin, epichlorohydrin, and epicyclohexane.

[0008] Optionally, the branching agent has the following structural formula: Where m is a natural number from 1 to 50; n is a natural number from 1 to 50, and R1 is... , and One of them, R2 is , , and One of them.

[0009] The preparation method of the branching agent described above includes: Under anhydrous and oxygen-free conditions, epoxy compounds containing double bonds and epoxy compounds without double bonds are polymerized to obtain polymers. After cooling the polymer to room temperature, it was dissolved and precipitated repeatedly using chloroform and n-hexane, and then dried to obtain the branching agent.

[0010] Optionally, during the polymerization reaction, an initiator and a catalyst need to be added. The molar ratio of the catalyst to the total amount of epoxy compounds containing double bonds and epoxy compounds without double bonds is 1:(200-20000), and the molar ratio of the initiator to the total amount of epoxy compounds containing double bonds and epoxy compounds without double bonds is 1:(2-100).

[0011] Optionally, the catalyst is Zn3[Co(CN)6]2, and the initiator is one of benzyl alcohol, ethylene glycol, propylene glycol, butanediol, polyethylene glycol 400, and polypropylene glycol 200.

[0012] Optionally, the polymerization reaction temperature is 50–150°C, and the polymerization reaction time is 4–12 h.

[0013] A modified EVA, by mass parts, comprises 85-99.9 parts of ethylene-vinyl acetate copolymer, 0.01-2 parts of branching initiator, 0.01-3 parts of antioxidant, and 0.01-10 parts of the above-mentioned branching agent.

[0014] Optionally, the ethylene-vinyl acetate copolymer contains 5% to 40% vinyl acetate in molar percentage and has a melt index of 5. 15 g / 10 min; the branching initiator is azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, 1,1' azo The antioxidant is one of cyanocyclohexane, benzoyl peroxide, tert-butyl peroxide-2-ethylhexyl carbonate, di(hexadecyl)dicarbonate peroxide, 2,4-di-tert-butylperoxide isopropylbenzene, and dicumyl peroxide; the antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-p-cresol, and tris[2,4-di-tert-butylphenyl]phosphite.

[0015] The preparation method of the modified EVA described above includes: Modified EVA is obtained by melt mixing ethylene-vinyl acetate copolymer, branching initiator, antioxidant and branching agent at 100-190℃.

[0016] Alternatively, a mixer or screw extruder may be used for melt mixing.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a branching agent containing a double bond structure. Under high-temperature processing conditions, this agent readily reacts with a branching initiator to generate branching agent free radicals. At high temperatures, hydrogen atoms bonded to tertiary carbon atoms in the EVA backbone are easily lost, generating EVA backbone free radicals. These branching agent free radicals combine with EVA backbone free radicals to form a branched structure. Simultaneously, this branching agent can also connect different EVA molecular chains to form long-chain branched structures, increasing intermolecular entanglement and interaction, thereby reducing the melt index and increasing tensile strength. The branching agent exhibits high branching efficiency, and the degree of EVA branching can be influenced by adjusting the amount of branching agent or the double bond content within it, thus allowing for the adjustment of properties such as the melt index and tensile strength of the modified EVA.

[0018] The present invention also provides a method for preparing the above-mentioned branching agent. The method involves introducing a catalyst and a co-initiator to copolymerize an epoxy compound containing double bonds with an epoxy compound without double bonds, and repeatedly dissolving and precipitating the copolymer to obtain a pure branching agent. The method is simple, the reaction conditions are mild, the equipment cost is low, and the preparation route is efficient, low in energy consumption, and has no waste discharge. It is an atom-economical route. At the same time, the raw materials used are inexpensive and readily available, making it easy to industrialize and showing good application prospects.

[0019] This invention provides a modified EVA, the raw material components of which include ethylene-vinyl acetate copolymer, branching initiator, antioxidant, and the aforementioned branching agent. Because the aforementioned branching agent contains a double bond structure, it can combine with the free radicals of the ethylene-vinyl acetate copolymer backbone under high temperature conditions to form a branched structure. At the same time, it connects different EVA molecular chains to form a long-chain branched structure, improving intermolecular entanglement and interaction, thereby enhancing the strength of EVA. The tensile strength of this modified EVA is 13.4 to 15.7 MPa, providing a solution for supercritical foaming processes.

[0020] The above-mentioned method for preparing modified EVA uses only existing equipment to melt-mix ethylene-vinyl acetate copolymer, branching initiator, antioxidant and the above-mentioned branching agent to obtain modified EVA with a tensile strength of 13.4 to 15.7 MPa, which provides a foundation for promoting the technological upgrading and sustainable development of related industries. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a method for preparing a branching agent according to the present invention.

[0022] Figure 2 The image shows the GPC spectrum of the branching agent prepared in Example 1 of this invention.

[0023] Figure 3 The nuclear magnetic resonance hydrogen spectrum of the branching agent prepared in Example 1 of this invention.

[0024] Figure 4 The image shows the DSC spectrum of the branching agent prepared in Example 1 of this invention. Detailed Implementation

[0025] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0026] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0027] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0028] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0029] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0031] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0032] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0033] This invention discloses a branching agent, which is obtained by copolymerizing an epoxy compound containing double bonds with an epoxy compound without double bonds. The epoxy compound containing double bonds includes one of 3,4-epoxy-1-butene, 4,5-epoxy-1-cyclohexene, and 4,5-epoxy-3-methyl-1-cyclohexene; the epoxy compound without double bonds includes one of ethylene oxide, epichlorohydrin, epichlorohydrin, and epicyclohexane.

[0034] The structural formula of the branching agent is: Where m is a natural number from 1 to 50; n is a natural number from 1 to 50, and R1 is... , and One of them, R2 is , , and One of them.

[0035] The structural formula of the epoxy compound containing double bonds is as follows: , or .

[0036] The epoxy compound that does not contain double bonds is , , or .

[0037] The molar ratio of the epoxy compound containing double bonds to the epoxy compound without double bonds is (0.1-9):1.

[0038] See Figure 1 The present invention also provides a method for preparing the branching agent as described above, comprising: S1: Under anhydrous and oxygen-free conditions, an epoxy compound containing double bonds and an epoxy compound without double bonds are polymerized to obtain a polymer, specifically: Under anhydrous and oxygen-free conditions, an epoxy compound containing double bonds and an epoxy compound without double bonds are mixed in a molar ratio of (0.1–9):1 and placed in a high-temperature reactor. An initiator and a catalyst are added, and the polymerization reaction is carried out at 50–150°C for 4–12 hours to obtain a polymer. The molar ratio of the catalyst to the total amount of the epoxy compound containing double bonds and the epoxy compound without double bonds is 1:(200–20000), and the molar ratio of the initiator to the total amount of the epoxy compound containing double bonds and the epoxy compound without double bonds is 1:(2–100). The catalyst is Zn3[Co(CN)6]2, and the initiator is one of benzyl alcohol, ethylene glycol, propylene glycol, butanediol, polyethylene glycol 400, and polypropylene glycol 200.

[0039] S2: After cooling the polymer to room temperature, it is dissolved and precipitated repeatedly using chloroform and n-hexane alternately, followed by drying to obtain the branching agent, specifically: After cooling the polymer to room temperature, chloroform was added to the reactor to completely dissolve the polymer. The resulting product was precipitated with n-hexane, dissolved, and precipitated repeatedly. After vacuum drying to constant weight, the purified branching agent was obtained.

[0040] The present invention also provides a modified EVA, wherein, by mass parts, the raw material components include 85-99.9 parts of ethylene-vinyl acetate copolymer, 0.01-2 parts of branching initiator, 0.01-3 parts of antioxidant, and 0.01-10 parts of the above-mentioned branching agent.

[0041] The ethylene-vinyl acetate copolymer contains 5% to 40% vinyl acetate in molar percentage and has a melt index of 5. 15g / 10min; the branching initiator is azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, 1,1' azo The antioxidant is one of cyanocyclohexane, benzoyl peroxide, tert-butyl peroxide-2-ethylhexyl carbonate, di(hexadecyl)dicarbonate peroxide, 2,4-di-tert-butylperoxide isopropylbenzene, and dicumyl peroxide; the antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-p-cresol, and tris[2,4-di-tert-butylphenyl]phosphite.

[0042] The method for preparing the modified EVA is as follows: Modified EVA is obtained by melt mixing ethylene-vinyl acetate copolymer, branching initiator, antioxidant and branching agent at 100-190℃.

[0043] Preferably, a mixer or screw extruder is used for melt mixing.

[0044] Example 1 A 50 mL autoclave equipped with a mechanical stirrer was dried at 120 °C for more than 12 h. After evacuation, it was allowed to cool to room temperature and then purged with nitrogen for use. Under nitrogen protection, 3,4-epoxy-1-butene (3.5 g, 0.05 mol) and cyclohexane oxide (4.9 g, 0.05 mol) were weighed at room temperature and added to the autoclave, along with Zn3[Co(CN)6]2 (8.4 mg) and polypropylene glycol 200 (0.84 g, 4.2 mmol). The autoclave was sealed, and the polymerization reaction temperature was set to 80 °C for 4 h. The autoclave was cooled to room temperature. After the reaction, the polymer sample was allowed to cool to room temperature, and chloroform was added to the autoclave to completely dissolve the polymer. The resulting product was precipitated with n-hexane, dissolved, and precipitated repeatedly. The product was then dried under vacuum to constant weight to obtain the purified branching agent.

[0045] Example 2 A 50 mL autoclave equipped with a mechanical stirrer was dried at 120℃ for more than 12 hours. After evacuation, it was allowed to cool to room temperature and then purged with nitrogen for use. Under nitrogen protection, 0.01 mol of 4,5-epoxy-1-cyclohexene and 0.1 mol of epichlorohydrin were weighed at room temperature and added to the autoclave, along with 0.55 mmol of Zn3[Co(CN)6]2 and 55 mmol of benzyl alcohol. The autoclave was sealed, and the polymerization reaction temperature was set to 50℃ for 12 hours. The autoclave was cooled to room temperature. After the reaction, the polymer sample was allowed to cool to room temperature, and chloroform was added to the autoclave to completely dissolve the polymer. The resulting product was precipitated with n-hexane, dissolved, and precipitated repeatedly. The product was then dried under vacuum to constant weight to obtain the purified branching agent.

[0046] Example 3 A 50 mL autoclave equipped with a mechanical stirrer was dried at 120℃ for more than 12 hours. After evacuation, it was allowed to cool to room temperature and then purged with nitrogen for use. Under nitrogen protection, 0.45 mol of 4,5-epoxy-3-methyl-1-cyclohexene and 0.05 mol of epichlorohydrin were weighed and added to the autoclave, along with 0.25 mmol of Zn3[Co(CN)6]2 and 50 mmol of ethylene glycol. The autoclave was sealed, and the polymerization reaction temperature was set to 100℃ for 8 hours. The autoclave was cooled to room temperature. After the reaction, the polymer sample was allowed to cool to room temperature, and chloroform was added to the autoclave to completely dissolve the polymer. The resulting product was precipitated with n-hexane, dissolved, and precipitated repeatedly. The product was then dried under vacuum to constant weight to obtain the purified branching agent.

[0047] Example 4 A 50 mL autoclave equipped with a mechanical stirrer was dried at 120℃ for more than 12 hours. After evacuation, it was allowed to cool to room temperature and then purged with nitrogen for use. Under nitrogen protection, 0.4 mol of 3,4-epoxy-1-butene and 0.05 mol of cyclohexane oxide were weighed at room temperature and added to the autoclave, along with 21.8 mmol of Zn3[Co(CN)6] and 9 mmol of polyethylene glycol 400. The autoclave was sealed, and the polymerization reaction temperature was set to 110℃ for 7 hours. The autoclave was then cooled to room temperature. After the reaction, the polymer sample was allowed to cool to room temperature, and chloroform was added to the autoclave to completely dissolve the polymer. The resulting product was precipitated with n-hexane, dissolved, and precipitated repeatedly. The product was then dried under vacuum to constant weight to obtain the purified branching agent.

[0048] Example 5 A 50 mL autoclave equipped with a mechanical stirrer was dried at 120°C for at least 12 hours. After evacuation, it was allowed to cool to room temperature and then purged with nitrogen for use. Under nitrogen protection, 0.2 mol of 4,5-epoxy-3-methyl-1-cyclohexene and 0.05 mol of epichlorohydrin were weighed and added to the autoclave, along with 0.5 mmol of Zn3[Co(CN)6]2 and 3.125 mmol of butanediol. The autoclave was sealed, and the polymerization reaction temperature was set to 120°C for 4 hours. The autoclave was then cooled to room temperature. After the reaction, the polymer sample was allowed to cool to room temperature, and chloroform was added to the autoclave to completely dissolve the polymer. The resulting product was precipitated with n-hexane, dissolved, and precipitated repeatedly. The product was then dried under vacuum to constant weight to obtain the purified branching agent.

[0049] The branching agent prepared in Example 1 was subjected to GPC testing, see [reference needed]. Figure 2 The results showed that the branching agent polymer had a number-average molecular weight of 2.2 kg / mol and a molecular weight distribution of 1.65. The 1H NMR spectrum is shown below. Figure 3 The results showed that the molar content of 3,4-epoxy-1-butene structural units in the branching agent was 48.7%. Thermal performance tests can be found [link to relevant documentation]. Figure 4 The results showed that the glass transition temperature of the obtained branching agent was 38.2 ℃.

[0050] Example 6 1000g of ethylene-vinyl acetate copolymer (EVA) was taken and mixed with the branching agent (10g), benzoyl peroxide (10g), antioxidant 1010 (1g, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), and antioxidant 168 (1g, tris[2,4-di-tert-butylphenyl]phosphite) prepared in Example 1. After high-speed stirring and mixing, the mixture was melt-mixed using a twin-screw extruder. The extruder feeding section temperatures were set as follows: zone 1 100℃, zones 2-8 160℃, zone 9 130℃, and zone 10 100℃; the die temperature was set to 100℃, and the screw speed was set to 100rpm. After EVA melt extrusion, the melt index and strength of the EVA were tested.

[0051] Example 7 1000g of ethylene-vinyl acetate copolymer (EVA) was taken and mixed with the branching agent (90g), azobisisobutyronitrile (20g), antioxidant 1010 (0.1g), and antioxidant 168 (0.1g) prepared in Example 1. After high-speed stirring and mixing, the mixture was melt-extruded using a twin-screw extruder. The extruder feeding section temperatures were set as follows: Zone 1 100℃, Zones 2-8 160℃, Zone 9 130℃, and Zone 10 100℃; the die temperature was set to 100℃, and the screw speed was set to 100rpm. After EVA melt extrusion, the melt index and strength of the EVA were tested.

[0052] Example 8 1000g of ethylene-vinyl acetate copolymer (EVA) was taken and mixed with the branching agent (10g), dic(hexadecyl)dicarbonate peroxide (10g), antioxidant 1076 (2g, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl alcohol ester), and antioxidant 264 (2g, tris[2,4-di-tert-butylphenyl]phosphite) prepared in Example 1. After high-speed stirring and mixing, the mixture was melt-mixed using a twin-screw extruder. The extruder feeding section temperatures were set as follows: Zone 1 100℃, Zones 2-8 160℃, Zone 9 130℃, and Zone 10 100℃; the die temperature was set to 100℃, and the screw speed was set to 100rpm. After EVA melt extrusion, the melt index and strength of the EVA were tested.

[0053] Example 9 Take 1000g of ethylene-vinyl acetate copolymer (EVA), add 10g of the branching agent prepared in Example 1, 1,1' azo Cyanocyclohexane (10g), antioxidant 1010 (1g, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), and antioxidant 168 (1g, tris[2,4-di-tert-butylphenyl]phosphite) were mixed at high speed and then melt-blended using a twin-screw extruder. The extruder's feeding section temperatures were set as follows: Zone 1 100℃, Zones 2-8 160℃, Zone 9 130℃, and Zone 10 100℃; the die temperature was set to 100℃, and the screw speed was set to 100 rpm. After EVA melt extrusion, the melt index and strength of the EVA were tested.

[0054] Example 10 1000g of ethylene-vinyl acetate copolymer (EVA) was taken and mixed with the branching agent (30g), 2-ethylhexyl carbonate tert-butyl peroxide (10g), antioxidant 1010 (30g, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant 168 (30g, tris[2,4-di-tert-butylphenyl]phosphite) prepared in Example 1. After high-speed stirring and mixing, the mixture was melt-mixed using a twin-screw extruder. The extruder feeding section temperatures were set as follows: zone 1 100℃, zones 2-8 160℃, zone 9 130℃, and zone 10 100℃; the die temperature was set to 100℃, and the screw speed was set to 100rpm. After EVA melt extrusion, the melt index and strength of the EVA were tested.

[0055] Example 11 1000g of ethylene-vinyl acetate copolymer (EVA) was taken and mixed with the branching agent (60g), 2,4-di-tert-butylperoxyisopropylbenzene (15g), antioxidant 1010 (1g, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant 168 (1g, tris[2,4-di-tert-butylphenyl]phosphite) prepared in Example 1. After high-speed stirring and mixing, the mixture was melt-mixed using a twin-screw extruder. The extruder feeding section temperatures were set as follows: zone 1 100℃, zones 2-8 160℃, zone 9 130℃, and zone 10 100℃; the die temperature was set to 100℃, and the screw speed was set to 100rpm. After EVA melt extrusion, the melt index and strength of the EVA were tested.

[0056] Example 12 1000g of ethylene-vinyl acetate copolymer (EVA) was taken and mixed with the branching agent (50g), dicumyl peroxide (10g), antioxidant 1010 (1g, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant 168 (1g, tris[2,4-di-tert-butylphenyl]phosphite) prepared in Example 1. After high-speed stirring and mixing, the mixture was melt-mixed using a twin-screw extruder. The extruder feeding section temperatures were set as follows: zone 1 100℃, zones 2-8 160℃, zone 9 130℃, and zone 10 100℃; the die temperature was set to 100℃, and the screw speed was set to 100rpm. After EVA melt extrusion, the melt index and strength of the EVA were tested.

[0057] Example 13 1000g of ethylene-vinyl acetate copolymer (EVA) was taken and mixed with the branching agent (30g), azobisisobutyronitrile (10g), antioxidant 1010 (1000ppm, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant 168 (1000ppm, tris[2,4-di-tert-butylphenyl]phosphite) prepared in Example 1. After high-speed stirring and mixing, the mixture was melt-mixed using a twin-screw extruder. The extruder feeding section temperatures were set as follows: zone 1 100℃, zones 2-8 160℃, zone 9 130℃, and zone 10 100℃; the die temperature was set to 100℃, and the screw speed was set to 100rpm. After EVA melt extrusion, the melt index and strength of the EVA were tested.

[0058] Example 14 1000g of ethylene-vinyl acetate copolymer (EVA) was taken and mixed with the branching agent (30g), azobisisovalerate (15g), antioxidant 1010 (1g, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant 168 (1g, tris[2,4-di-tert-butylphenyl]phosphite) prepared in Example 1. After high-speed stirring and mixing, the mixture was melt-mixed using a twin-screw extruder. The extruder feeding section temperatures were set as follows: zone 1 100℃, zones 2-8 160℃, zone 9 130℃, and zone 10 100℃; the die temperature was set to 100℃, and the screw speed was set to 100rpm. After EVA melt extrusion, the melt index and strength of the EVA were tested.

[0059] Comparative Example 1000g of ethylene-vinyl acetate copolymer (EVA) was taken, and benzoyl peroxide (10g), antioxidant 1010 (1g), and antioxidant 168 (1g) were added. After high-speed mixing, the mixture was melt-extruded using a twin-screw extruder. The extruder feeding section temperatures were set as follows: Zone 1 100℃, Zones 2-8 160℃, Zone 9 130℃, and Zone 10 100℃; the die temperature was set to 100℃, and the screw speed was set to 100rpm. After EVA melt extrusion, the melt index and strength of the EVA were tested.

[0060] The EVA prepared in Examples 6-14 and the comparative examples were tested, and the results are shown in the table below: sample Melt index (g / 10min) Vitamin A content (wt%) Tensile strength (MPa) Pure ethylene-vinyl acetate copolymer 12.0 33 8.7 Example 6 2.0 33 13.4 Example 7 0.2 33 15.7 Example 8 2.3 33 13.0 Example 9 4.2 33 12.1 Example 10 2.5 33 12.8 Example 11 1.9 33 13.6 Example 12 2.5 33 12.8 Example 13 3.3 33 12.4 Example 14 3.0 33 12.6 Comparative Example 7.4 33 10.1 It is evident that the branching agent prepared by this invention can effectively improve the tensile strength of EVA, providing a solution for supercritical foaming processes.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A branching agent, characterized in that, The branching agent is obtained by copolymerizing an epoxy compound containing double bonds with an epoxy compound without double bonds. The epoxy compound containing double bonds includes one of 3,4-epoxy-1-butene, 4,5-epoxy-1-cyclohexene, and 4,5-epoxy-3-methyl-1-cyclohexene. The epoxy compound without double bonds includes one of ethylene oxide, epichlorohydrin, epichlorohydrin, and epicyclohexane.

2. The branching agent according to claim 1, characterized in that, The structural formula of the branching agent is: Where m is a natural number from 1 to 50; n is a natural number from 1 to 50, and R1 is... , and One of them, R2 is , , and One of them.

3. The method for preparing the branching agent as described in claim 1 or 2, characterized in that, include: Under anhydrous and oxygen-free conditions, epoxy compounds containing double bonds and epoxy compounds without double bonds are polymerized to obtain polymers. After cooling the polymer to room temperature, it was dissolved and precipitated repeatedly using chloroform and n-hexane, and then dried to obtain the branching agent.

4. The method for preparing the branching agent according to claim 3, characterized in that, During the polymerization reaction, an initiator and a catalyst are required. The molar ratio of the catalyst to the total amount of epoxy compounds containing double bonds and epoxy compounds without double bonds is 1:(200-20000), and the molar ratio of the initiator to the total amount of epoxy compounds containing double bonds and epoxy compounds without double bonds is 1:(2-100).

5. The method for preparing the branching agent according to claim 4, characterized in that, The catalyst is Zn3[Co(CN)6]2, and the initiator is one of benzyl alcohol, ethylene glycol, propylene glycol, butanediol, polyethylene glycol 400, and polypropylene glycol 200.

6. The method for preparing the branching agent according to claim 3, characterized in that, The polymerization reaction is carried out at a temperature of 50–150°C for 4–12 hours.

7. A modified EVA, characterized in that, The raw material components, by mass, include 85 to 99.9 parts of ethylene-vinyl acetate copolymer, 0.01 to 2 parts of branching initiator, 0.01 to 3 parts of antioxidant, and 0.01 to 10 parts of the branching agent as described in claim 1 or 2.

8. The modified EVA according to claim 7, characterized in that, The ethylene-vinyl acetate copolymer contains 5% to 40% vinyl acetate in molar percentage and has a melt index of 5. 15 g / 10 min; the branching initiator is azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, 1,1' azo The antioxidant is one of cyanocyclohexane, benzoyl peroxide, tert-butyl peroxide-2-ethylhexyl carbonate, di(hexadecyl)dicarbonate peroxide, 2,4-di-tert-butylperoxide isopropylbenzene, and dicumyl peroxide; the antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-p-cresol, and tris[2,4-di-tert-butylphenyl]phosphite.

9. The method for preparing modified EVA as described in claim 8 or 9, characterized in that, include: Modified EVA is obtained by melt mixing ethylene-vinyl acetate copolymer, branching initiator, antioxidant and branching agent at 100-190℃.

10. The method for preparing modified EVA according to claim 9, characterized in that, The mixture is melt-mixed using an internal mixer or a screw extruder.

Images