Titanium-oxygen-carbon dynamic bond cross-linked polyethylene with reprocessability and preparation method of titanium-oxygen-carbon dynamic bond cross-linked polyethylene

Abstract

The invention relates to titanium-oxygen-carbon dynamic bond cross-linked polyethylene with repeatable processability and a preparation method of the titanium-oxygen-carbon dynamic bond cross-linked polyethylene. The titanium-oxygen-carbon dynamic bond crosslinked polyethylene is shown as a formula (I), x is an integer of 10-5000, y is an integer of 5-5000, x and y can be the same or different, and m is an integer of 0-(y-1); r is C1-C20 alkyl with or without heteroatoms, and the heteroatoms are O, N, P or S or other heteroatoms. The titanium-oxygen-carbon dynamic bond crosslinked polyethylene disclosed by the invention is simple in preparation method, free of a catalyst, low in cost, excellent in performance and very wide in industrial prospect. More importantly, the titanium-oxygen-carbon dynamic bond crosslinked polyethylene disclosed by the invention can be reprocessed and is a novel glass-like polymer. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of new polymer materials, and in particular relates to a titanium oxane cross-linked polyethylene with repeatable processability and a preparation method thereof. Background Art

[0002] Ethylene-vinyl acetate (EVA) resin is an important chemical product produced by ethylene and vinyl acetate (VAc) as raw materials. It has good optical properties, impact resistance, environmental stress cracking resistance, low melting temperature, excellent fluidity and nontoxicity. It is widely used in the fields of wires and cables, films, hot melt adhesives, photovoltaics, foaming, coating, heat sealing and welding. EVA is widely used in many fields such as foam, packaging materials, wires and cables after cross-linking. However, the permanent cross-linked network structure formed by traditional peroxide cross-linked EVA causes it to be difficult to recycle and reprocess, and then causes serious waste of resources and environmental pollution (Synthetic Materials Aging and Application, 2011, 40 (05), 7-11). Therefore, it is necessary to develop a new cross-linked EVA material with simple preparation method and repeatable recycling, which has important social and economic value.

[0003] Vitrimer is a new type of polymer material formed by dynamic chemical bond crosslinking, and related research and development work has progressed rapidly in recent years. Under operating conditions, the dynamic chemical bond crosslinking points in the Vitrimer structure do not undergo an exchange process, thus having excellent properties such as high rigidity and high heat resistance similar to traditional cross-linked polymers. Under processing conditions, the dynamic chemical bonds are rapidly exchanged and the crosslinking points are unlocked, giving Vitrimer the excellent processing properties of traditional thermoplastic polymers. Therefore, Vitrimer is a cross-linked polymer with reproducible processability composed of a dynamic chemical bond crosslinking network (Progress in Polymer Science, 2020, 104, 101233).

[0004] Patent CN102827448A uses alkenyl alkoxysilane and polyethylene resin to prepare a silane cross-linked polyethylene; Patent CN105143336A uses the condensation reaction between silanol-terminated polysiloxane and alkoxysilyl functionalized polyethylene to prepare cross-linked polyethylene with polysiloxane cross-linking bonds; Patent CN113817186B uses the transesterification reaction between silane cross-linking agent and ethylene / vinyl acetate copolymer to prepare siloxane cross-linked polyethylene. However, the cross-linked polyethylene proposed in Patent CN102827448A and Patent CN105143336A does not have reprocessability and cannot be recycled and reused; Patent CN113817186B requires the use of expensive cross-linking agents, which significantly increases the raw material cost of cross-linked polymers. Summary of the invention

[0005] In order to solve the problems of the prior art, the present invention provides a titanium oxygen carbon dynamic bond cross-linked polyethylene with repeatable processability and a preparation method thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] A titanium oxygen carbon dynamic bond cross-linked polyethylene with reproducible processability, the structural formula of which is shown in formula (I):

[0008]

[0009] in:

[0010] x is an integer of 10 to 5000, preferably 20 to 2000; y is an integer of 5 to 5000, preferably 10 to 1000; x and y may be the same or different, and m is an integer of 0 to (y-1);

[0011] R is a C1-C20 alkyl group (preferably C1-C5), with or without heteroatoms, wherein the heteroatoms are O, N, P or S and the like.

[0012] The present invention also provides a method for preparing the titanium oxycarbon dynamic bond cross-linked polyethylene with reproducible processability as shown in the above formula (I), the method comprising the following steps:

[0013] The ethylene / vinyl acetate copolymer shown in formula (III) is in a molten state or dissolved in an organic solvent, and then undergoes a crosslinking reaction with a titanate crosslinking agent shown in formula (II) to obtain a titanium oxycarbon dynamic bond crosslinked polyethylene shown in formula (I); the titanium oxycarbon dynamic bond crosslinked polyethylene is obtained by an ester exchange reaction between the ethylene / vinyl acetate copolymer shown in formula (III) and the titanate crosslinking agent shown in formula (II);

[0014] in,

[0015] x is an integer of 10 to 5000, y is an integer of 5 to 5000; x and y may be the same or different, and m is an integer of 0 to (y-1);

[0016] R is a C1-C20 alkyl group, with or without heteroatoms, wherein the heteroatoms are O, N, P, S and the like.

[0017]

[0018] According to the present invention, the molar ratio of the ethylene / vinyl acetate copolymer represented by formula (III) to the titanate crosslinking agent represented by (II) is 1:2 to y / 4; the molar ratio of the ethylene / vinyl acetate copolymer represented by formula (III) to the organic solvent is 1:50 to 5000, preferably 1:500 to 2000.

[0019] According to the present invention, the organic solvent is one or more of toluene, benzene, chlorobenzene, xylene, hexane, heptane, dichlorobenzene, trichlorobenzene, dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

[0020] For the above technical solution, the cross-linking reaction can be carried out in an organic solvent or in a molten state; when the reaction is carried out in an organic solvent, the steps are as follows: react at 70-160°C for 1-30 hours under the protection of an inert gas (nitrogen, argon, etc.), then precipitate the polymer with methanol or ethanol, wash, and vacuum dry at 30-80°C for 6-24 hours to remove the solvent. When the reaction is carried out in a molten state, the steps are as follows: react at 100-200°C in a molten state for 0.1-5 hours, and then continue to cure in a vacuum oven at 50-200°C for 0.1-24 hours.

[0021] For the above technical solution, under preferred circumstances, the ethylene / vinyl acetate copolymer shown in formula (III) has a vinyl acetate (VA) content of 1 to 50 wt%, preferably 5 to 30 wt%; a number average molecular weight of 720 to 500,000 g / mol, preferably 1,500 to 100,000 g / mol; and a polydispersity coefficient of 1 to 20, preferably 3 to 10.

[0022] The titanium oxygen carbon dynamic bond cross-linked polyethylene provided by the present invention has abundant raw material sources, a simple and efficient preparation method, low cost, excellent performance, and a very broad industrialization prospect. More importantly, the titanium oxygen carbon dynamic bond cross-linked polyethylene of the present invention has repeatable processability, does not require the introduction of catalysts, reduces reaction costs, and can be formed multiple times under processing conditions similar to those of ordinary polyethylene (such as 180-220°C, 20-60 minutes), and is a new type of glass-like polymer with excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a comparison diagram of the stress-strain curves of the titanium oxycarbon dynamic bond cross-linked polyethylene prepared in Example 3.

[0024] Figure 2 This is a photo of the reprocessing of the titanium oxycarbon dynamic bond cross-linked polyethylene prepared in Example 3.

[0025] Figure 3 Fourier transform infrared spectra of the original EVA and the titanium oxycarbon dynamic bond cross-linked polyethylene prepared in Example 3. DETAILED DESCRIPTION

[0026] The following non-limiting embodiments may enable a person of ordinary skill in the art to more fully understand the present invention, but do not limit the present invention in any way. Any person familiar with the present technical field may make equivalent replacements or changes according to the technical solution and inventive concept of the present invention within the technical scope disclosed by the present invention, which shall fall within the protection scope of the present invention.

[0027] The vinyl acetate copolymers in Examples 3 and 5 in the following examples are commercially available, and the vinyl acetate copolymers in Examples 1, 2, and 4 are homemade according to the literature (Xue Xiaoxian, Tian Li, Hong Song, Zhang Shu, Wu Yixian. Ind. Eng. Chem. Res. 2019, 58, 4125-4136). The cross-linking agents and organic solvents in the following examples are commercially available.

[0028] Example 1

[0029] In a 500ml two-necked bottle, add 20g of ethylene / vinyl acetate copolymer (EVA, number average molecular weight Mn = 2000g / mol, polydispersity index PDI = 7.0, VA content of 42wt%), vacuum dry at 40℃ for 0.5 hours, fill with nitrogen, add 200ml toluene and 0.9ml tetraethyl titanate, heat to 100℃, and stir to fully dissolve the polymer. After reacting for about 1h, the polymer system is in a gel state. After continuing to react for 5h, the product is repeatedly washed and soaked with a large amount of ethanol. After filtering, the solid product is vacuum dried at 80℃ for 12h to obtain titanium oxygen carbon dynamic bond cross-linked polyethylene.

[0030] To determine the gel fraction, weigh a small piece of the cross-linked polymer (m i ) and placed it in a flask to which approximately 50 mL of xylene was added. The polymer was then swollen by heating to 70°C for 16 h. This allowed the uncrosslinked polymer chains to diffuse into the excess solvent, leaving the crosslinked network in a swollen state. The swollen sample was then removed from the solvent and dried in a heated vacuum oven to remove any residual solvent (m d ). The calculation formula of gel fraction is:

[0031]

[0032] The swelling test results show that the gel fraction of the titanium oxycarbon dynamic bond cross-linked polyethylene is 79wt%.

[0033] Example 2

[0034] In a 250ml two-necked bottle, add 15g of ethylene / vinyl acetate copolymer (EVA, number average molecular weight Mn = 62000g / mol, polydispersity index PDI = 3.1, VA content of 6wt%), vacuum dry at 40℃ for 0.5 hours, fill with nitrogen, add 150ml of o-dichlorobenzene and 0.45ml of tetraisopropyl titanate, heat to 130℃, and stir to fully dissolve the polymer. After reacting for about 0.5h, the polymer system is in a gel state. After continuing to react for 5h, the product is repeatedly washed and soaked with a large amount of ethanol. After filtering, the solid product is vacuum dried at 80℃ for 12h to obtain titanium oxygen carbon dynamic bond cross-linked polyethylene.

[0035] The swelling test method was the same as that in Example 1. The results showed that the gel fraction of the titanium oxycarbon dynamic bond cross-linked polyethylene was 50 wt %.

[0036] Example 3

[0037] In a laboratory internal mixer with a volume of 50 ml, add 45 g of ethylene / vinyl acetate copolymer (EVA, number average molecular weight Mn = 347000 g / mol, polydispersity index PDI = 4.2, VA content of 28 wt%) and 2.25 g of tetrabutyl titanate, heat to 150 ° C, stir for 0.5 h to fully mix the materials. Collect the product and vacuum dry it at 120 ° C for 12 h to obtain titanium oxygen carbon dynamic bond cross-linked polyethylene.

[0038] The swelling test method was the same as that in Example 1, and the results showed that the gel fraction of the titanium oxygen carbon dynamic bond cross-linked polyethylene was 70 wt %. The infrared spectrum results showed that Ti-OC dynamic bonds appeared in the product.

[0039] Example 4

[0040] In a 500ml laboratory internal mixer, add 450g of ethylene / vinyl acetate copolymer (EVA, number average molecular weight Mn = 72000g / mol, polydispersity index PDI = 3.0, VA content of 15wt%) and 23ml of di(acetylacetonato) diisopropyl titanate, heat to 130°C, stir for 0.5h to fully mix the materials. Collect the product and vacuum dry it at 120°C for 12h to obtain titanium oxygen carbon dynamic bond cross-linked polyethylene.

[0041] The swelling test method was the same as that in Example 1. The results showed that the gel fraction of the titanium oxycarbon dynamic bond cross-linked polyethylene was 35 wt %.

[0042] Example 5

[0043] In a laboratory internal mixer with a volume of 500 ml, add 460 g of ethylene / vinyl acetate copolymer (EVA, number average molecular weight Mn = 116000 g / mol, polydispersity index PDI = 5.5, VA content of 33 wt%) and 140 ml of isopropyl triisostearate titanate, heat to 150 ° C, stir for 1 hour to fully mix the materials. Collect the product and vacuum dry it at 160 ° C for 10 hours to obtain titanium oxygen carbon dynamic bond cross-linked polyethylene.

[0044] The swelling test method was the same as that in Example 1. The results showed that the gel fraction of the titanium oxycarbon dynamic bond cross-linked polyethylene was 40 wt %.

[0045] Example 6

[0046] Reprocessability test:

[0047] The titanium oxycarbon dynamic bond cross-linked polyethylene prepared in Example 3 was crushed into irregular small pieces (about 3×3×3mm in size) using a crusher, and then kept at 180℃ and 5t pressure for 0.5h using a flat vulcanizer to obtain a dumbbell-shaped spline A with uniform material, which proves that the prepared titanium oxycarbon dynamic bond cross-linked polyethylene has good reprocessability. The dumbbell-shaped spline was used for polymer tensile property testing. The broken dumbbell-shaped spline A was then crushed and hot-pressed again according to the above conditions to form a dumbbell-shaped spline B. The mechanical property test showed that the tensile properties of spline A and spline B were close, which confirmed that the titanium oxycarbon dynamic bond cross-linked polyethylene was reprocessable, and there was no obvious loss in performance after repeated crushing and processing compared with before crushing (as shown in the following table).

[0048]

Claims

1. A titanium oxycarbon dynamic bond cross-linked polyethylene with reproducible processability, characterized in that: Its structure is shown in formula (I): in: x is an integer from 10 to 5000, y is an integer from 5 to 5000, and m is an integer from 0 to (y-1); R is a C1-C20 alkyl group.

2. The titanium oxycarbon dynamic bond cross-linked polyethylene with reproducible processability according to claim 1, characterized in that: x and y are the same or different; R may or may not have a heteroatom, and the heteroatom is O, N, P or S.

3. A titanium oxycarbon dynamic bond cross-linked polyethylene with reproducible processability and a preparation method thereof according to claim 1 or 2, characterized in that: The method comprises the following steps: The ethylene / vinyl acetate copolymer shown in formula (III) is in a molten state or dissolved in an organic solvent, and then crosslinked with a titanate crosslinking agent shown in formula (II) to obtain a titanium oxygen carbon dynamic bond crosslinked polyethylene shown in formula (I); in: x is an integer from 10 to 5000, y is an integer from 5 to 5000, and m is an integer from 0 to (y-1); R is a C1-C20 alkyl group.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the ethylene / vinyl acetate copolymer represented by formula (III) to the titanate crosslinking agent represented by (II) is 1:2 to y / 4; the molar ratio of the ethylene / vinyl acetate copolymer represented by formula (III) to the organic solvent is 1:50 to 5000.

5. The preparation method according to claim 3, characterized in that: The organic solvent is one or more of toluene, benzene, chlorobenzene, xylene, hexane, heptane, dichlorobenzene, trichlorobenzene, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide.

6. The preparation method according to claim 3, characterized in that: The cross-linking reaction is carried out in an organic solvent or in a molten state. When the reaction is carried out in an organic solvent, the steps are as follows: react at 70-160° C. for 1-30 hours under the protection of an inert gas; when the reaction is carried out in a molten state, the steps are as follows: react at 100-200° C. in a molten state for 0.1-5 hours, and then continue to cure at 50-200° C. in a vacuum oven for 0.1-24 hours.

7. The preparation method according to claim 3, characterized in that: The ethylene / vinyl acetate copolymer represented by formula (III) has a number average molecular weight of 720 to 500,000 g / mol and a polydispersity coefficient of 1 to 20.

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