A method for synthesizing aminated polyethylene

Abstract

The present invention discloses a method for synthesizing aminated polyethylene. Under the action of cheap metal salts, suitable temperature and light energy are provided, and nitrosobenzene compounds are used to post-functionalize the carbon-hydrogen bonds of polyethylene compounds, thereby achieving catalytic amination functionalization conversion to obtain aminated polyethylene. The present invention directly utilizes commercial polyethylene compounds or waste polyethylene plastics to functionalize carbon-hydrogen bonds. It has the advantages of simple reaction, simple operation, short reaction time, mild reaction conditions, high reaction efficiency, easy separation and purification of products, and good substrate universality. It avoids the use of large amounts of precious metals and heavy metal salts, is very attractive in industrial production, and has great application potential in the fields of polymer modification, new material synthesis, and waste plastic recycling. At the same time, the aminated polyethylene obtained by the present invention has good adhesion strength, and its adhesion performance is 5 to 10 times that of ordinary polyethylene materials, making it suitable for the development of new plastic adhesives.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer chemical synthesis, and particularly relates to a method for synthesizing aminated polyethylene. The method is a method for preparing a polyethylene product containing polar amine functional groups by breaking carbon-hydrogen bonds in the main chain of a polyethylene polymer compound and aminating the carbon-hydrogen bonds by catalysis of metal salts under visible light induction. Background Art

[0002] Polyethylene compounds are widely used in food packaging, medical devices, and daily necessities due to their low cost, availability, excellent physical properties, and chemical resistance. As one of the three major synthetic plastics, they play an irreplaceable role in human production and life. Currently, commercial polyethylene is composed entirely of inert carbon-carbon and carbon-hydrogen bonds, resulting in poor adhesion, compatibility, and printing and dyeing properties, limiting its application in some specialized fields. Furthermore, the widespread use of polyethylene plastics has also led to serious "white pollution," necessitating the recycling and upgrading of waste plastics.

[0003] Functionalization of carbon-hydrogen bonds on polyethylene chains is an important approach to modifying their structure, properties, and uses, thereby enabling the reuse and performance reengineering of discarded plastics, providing a promising solution for the sustainable recycling of plastic waste. Introducing carbon-nitrogen bonds into the polyolefin backbone, leveraging the polarity of heteroatoms and potential hydrogen bonding, can significantly alter the viscosity, hydrophilicity, and mechanical properties of polyethylene materials. However, conventional copolymerization strategies have made it difficult to synthesize polyethylene containing nitrogen functional groups, and examples of introducing nitrogen functional groups through post-functionalization strategies are also extremely rare. Therefore, novel strategies for introducing nitrogen functional groups into polyethylene are still needed. Summary of the Invention

[0004] In view of the shortcomings of the current technology, the purpose of the present invention is to provide a method for the visible light-induced metal salt-catalyzed amination of the carbon-hydrogen bonds of polyethylene compounds, which is applicable to polyethylene compounds of different molecular weights and structures, including polyethylene waste plastics. Under the promotion of cheap metal salts and additives, under the irradiation of visible light, the carbon-hydrogen bonds of polyethylene compounds are homolytically cleaved to produce macromolecular free radicals, which are then subjected to free radical addition to nitrosobenzene compounds to generate a series of polyethylene compounds with nitrogen-containing functional groups. This method has the advantages of mild reaction conditions and simple operation. This method provides a convenient and fast strategy for the preparation of a variety of nitrogen-containing polyethylene compounds. By directly utilizing cheap and abundant polyethylene compounds as raw materials, the use of large amounts of heavy metal salts and strong oxidants is avoided, which is very attractive in industrial production. At the same time, the use of cheap metals for reaction also has great application potential in the fields of waste plastic recycling and modification.

[0005] To achieve the above objectives, the present invention utilizes a synthesis method for aminated polyethylene. Under the action of an inexpensive metal salt, temperature and light energy are provided. In the presence of additives and a nitrosobenzene compounds as a nitrogenating agent, the polyethylene compound is subjected to cleavage and amination in a corresponding organic solvent, thereby obtaining a polar amino-functionalized product. The specific synthesis method is as follows: under the protection of an inert gas, a polyethylene compound, a nitrosobenzene compound, a metal salt, and an additive are added to an organic solvent. The reaction is stirred under heating and light irradiation to cleave the carbon-hydrogen bonds in the polyethylene compound chain and undergo amination. After the reaction is complete, the light is removed, ethanol is added to precipitate the solid, which is then filtered, washed, and vacuum-dried to obtain the aminated polyethylene. The reaction equation is as follows:

[0006]

[0007] The polyethylene compounds mentioned above are of any molecular weight, including low-density polyethylene, high-density polyethylene, linear low-density polyethylene, high-density polyethylene plastic bags, high-density polyethylene plastic bottles, low-density polyethylene plastic wrap, etc.

[0008] The general formula of the above-mentioned nitrosobenzene compounds is Wherein R represents a monosubstituted or disubstituted substituent on the benzene ring, selected from any one or two of hydrogen, phenoxy, phenyl, C1-C4 alkyl, chlorine, and fluorine, such as: hydrogen, para-phenoxy, phenyl, methyl, tert-butyl, chlorine, fluorine substitution, para-meta disubstituted methyl, para-methyl meta-chlorine substitution, etc.

[0009] The above-mentioned metal salt is any one of magnesium salt, iron salt, cerium salt, and copper salt; the magnesium salt is magnesium chloride, magnesium chloride hexahydrate, etc.; the iron salt is selected from trivalent iron salt or divalent iron salt, the trivalent iron salt is ferric chloride, tetrabutylferric tetrachloride, ferric nitrate nonahydrate, ferric acetylacetonate, etc., the divalent iron salt is ferrous chloride, ferrous sulfate heptahydrate, etc.; the cerium salt is cerium chloride, hydrated cerium chloride, etc.; the copper salt is copper chloride, copper trifluoroacetate, etc.

[0010] The above-mentioned additives include any one of an organic boron compound, an organic silicon compound, and an organic acid compound, wherein the organic boron compound is any one of bis(pyrocatechol) borate, phenylboric acid, cyclohexylboric acid, boron tribromide, bis(pinacolato)diboron, methylboric acid, and pinacol borane; the organic silicon compound is any one of diethylsilane, triethylsilane, and phenylsilane; and the organic acid compound is any one of benzoic acid, p-toluic acid, p-chlorobenzoic acid, cyclohexylcarboxylic acid, and p-toluenesulfonic acid.

[0011] Preferably, the additive further comprises any one of tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylammonium iodide.

[0012] The organic solvent is any one of an aromatic hydrocarbon solvent, a halogenated hydrocarbon solvent, an ether solvent, and a nitrile solvent. The aromatic hydrocarbon solvent includes benzene, toluene, trifluorotoluene, chlorobenzene, etc.; the halogenated hydrocarbon solvent includes dichloromethane, 1,2-dichloroethane, chloroform, carbon tetrachloride, etc.; the ether solvent includes tetrahydrofuran, 1,4-dioxane, methyl tert-butyl ether, diethyl ether, etc.; and the nitrile solvent includes acetonitrile, benzonitrile, tert-butyl acetonitrile, etc.

[0013] In the above synthesis method, it is further preferred that the metal salt is ferric chloride or tetrabutylferric tetrachloride, the additive is methylboric acid, and the organic solvent is chlorobenzene or 1,2-dichloroethane.

[0014] In the above synthesis method, the molar ratio of the metal salt to the ethylene structural unit in the polyethylene compound is preferably 0.004-0.012:1, the molar ratio of the nitrosobenzene compound to the ethylene structural unit in the polyethylene compound is 0.10-0.30:1; and the molar ratio of the additive to the ethylene structural unit in the polyethylene compound is 0.15-0.17:1.

[0015] In the above synthesis method, preferably, the heating temperature is 70 to 150° C., the irradiation is performed using visible light with a wavelength of 390 to 460 nm, and the stirring reaction time is 2 to 10 hours.

[0016] The present invention further provides a polyethylene adhesive, which is an aminated polyethylene obtained by the above-mentioned synthesis method. The adhesive has good adhesion strength, and the adhesion performance is 5 to 10 times that of ordinary polyethylene materials.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. This invention provides a one-step, efficient amination functionalization method for polyethylene polymer compounds, promoted by an inexpensive metal salt catalyst. This method yields aminated polyethylene materials, which are difficult to obtain through traditional copolymerization strategies. This invention also provides a method for functionalizing polyethylene waste plastics. Using heat and light energy, a metal salt catalyst, and additives, the corresponding polyethylene derivatives can be efficiently and quickly obtained.

[0019] 2. The present invention is simple to operate, has mild reaction conditions (visible light is used as a light source, and a low-power LED lamp can achieve the reaction), is redox neutral, has a short reaction time, and the product is easy to separate and purify. It is safe and green, and the reaction only requires cheap and readily available catalysts such as magnesium, iron, copper, and cerium, without the need for expensive metals. It is also widely applicable, and low-density polyethylene, high-density polyethylene, linear low-density polyethylene, high-density polyethylene plastic bags, high-density polyethylene plastic bottles, low-density polyethylene plastic wrap, and the like of different molecular weights can all be used as substrates. Nitrosobenzene compounds with various electron-withdrawing (fluorine, chlorine, and other groups) and electron-donating (methyl, phenoxy, and the like) groups can all be used as amine sources, enabling the rapid and simple synthesis of aminated polyethylene compounds of different structures.

[0020] 3. The aminated polyethylene obtained by the present invention has excellent adhesion strength, 5 to 10 times that of ordinary polyethylene materials, making it suitable for recycling waste plastics and developing new plastic adhesives. Furthermore, the aminated polyethylene product can be further derived to prepare other amine-containing polyethylene materials. The present method has great significance in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a comparison chart of the shear strength of low-density polyethylene, high-density polyethylene, and the aminated plastic bags, plastic bottles, and plastic wrap in Examples 31 to 33 on aluminum plates and steel plates. DETAILED DESCRIPTION

[0022] The following will be combined with the accompanying drawings and examples to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other unless there is a conflict. The following examples are helpful for understanding the present invention, but are not limited to the scope of protection of the present invention.

[0023] Examples 1 to 17

[0024] According to the raw material ratio and reaction conditions in Table 1, low-density polyethylene (LDPE, ethylene structural unit 2 mmol) with a number average molecular weight of 2.1 kDa, nitrosobenzene (x mmol), and additive 1 (0.30 mmol) were added to a 25 mL dry reaction tube in sequence. Metal salt (y mmol), additive 2 (y mmol), and organic solvent (3.0 mL) were added in a glove box. After the addition was completed, the reaction tube was removed from the glove box and placed in an oil bath at a set temperature, stirred and dissolved. After the reactants were completely dissolved, they were irradiated under visible light of different wavelengths and stirred continuously. After a certain reaction time, the reaction tube was removed from the light source, 10 mL of ethanol was added to precipitate the solid, stirred at room temperature for 5 to 10 minutes, filtered, and washed three times with 10 mL of dichloromethane and 10 mL of ethanol alternately until the small molecules were completely removed. The target product, aminated polyethylene, was obtained by vacuum drying.

[0025]

[0026] Table 1

[0027]

[0028]

[0029]

[0030] Examples 18 to 32

[0031] According to the raw material ratio and reaction conditions in Table 2, a polyethylene compound (ethylene structural unit 2 mmol), a nitrosobenzene compound (x mmol), and methylboric acid (0.30 mmol) were added to a 25 mL dry reaction tube in sequence. Tetrabutylferric tetrachloride (y mmol) and chlorobenzene (3.0 mL) were added in a glove box. After the addition was completed, the reaction tube was removed from the glove box and placed in an oil bath at a set temperature. Stirring and dissolving, after the reactants were completely dissolved, irradiated under visible light with a wavelength of 425 nm and continued stirring. After reacting for 2 hours, the reaction tube was removed from the light source, 10 mL of ethanol was added to precipitate the solid, stirred at room temperature for 5 to 10 minutes, filtered, and washed three times with 10 mL of dichloromethane and 10 mL of ethanol alternately until the small molecules were completely removed. The target product, aminated polyethylene, was obtained by vacuum drying.

[0032]

[0033] Table 2

[0034]

[0035]

[0036] In order to verify the practical application of the aminated polyethylene material, shear strength tests were performed on the products of Examples 30, 31, and 32 to further evaluate the adhesion properties of the functionalized waste plastics. Figure 1 Experimental data show that the maximum adhesion of ordinary low-density polyethylene and high-density polyethylene materials to steel and aluminum plates is less than 0.50MPa, while the maximum adhesion strength of functionalized discarded high-density polyethylene plastic bags to steel and aluminum plates can reach 2.5MPa, and the maximum adhesion strength of functionalized discarded high-density polyethylene plastic bottles to steel and aluminum plates can reach 3.5MPa. Functionalized discarded low-density polyethylene cling film has the best adhesion effect, with an adhesion strength of 4.0MPa to aluminum plates and up to 4.5MPa to steel plates. The viscosity of the waste plastics modified by the method of the present invention even exceeds that of some commercially available adhesives, indicating that the functionalized waste polyethylene materials have the potential to be used as adhesives. More importantly, the present invention further broadens the recycling and upgrading channels for waste plastics, increases the use value of waste plastics, and meets the economic requirements of green recycling.

[0037] As can be seen from the above embodiments and experimental results, the present invention can achieve functionalization of polyethylene compounds and their corresponding waste plastics under visible light irradiation and inexpensive metal salt catalysis conditions. The modified waste plastics are expected to be used as adhesives to achieve the recycling of waste plastics. There is no need to use harsh reaction conditions such as high temperature and strong oxidants or add precious metal catalysts. The reaction conditions are mild, green and environmentally friendly, suitable for industrial production, and provide a new strategy for the diversity of chemical synthesis.

Claims

1. A method for synthesizing aminated polyethylene, characterized in that: Under the protection of inert gas, polyethylene compounds, nitrosobenzene compounds, metal salts, and additives are added to an organic solvent, and stirred to react under heating and light conditions to break the carbon-hydrogen bonds on the polyethylene compound chain and aminize to obtain aminated polyethylene; The metal salt is any one of magnesium salt, iron salt, cerium salt and copper salt; The additive comprises any one of an organic boron compound, an organosilicon compound, and an organic acid compound; wherein the organic boron compound is any one of bis(pyrocatechol) borate, phenylboric acid, cyclohexylboric acid, boron tribromide, bis(pinacol)diboron, methylboric acid, and pinacol borane; the organosilicon compound is any one of diethylsilane, triethylsilane, and phenylsilane; and the organic acid compound is any one of benzoic acid, p-methylbenzoic acid, p-chlorobenzoic acid, p-toluenesulfonic acid, and cyclohexylcarboxylic acid; The nitrosobenzene compound is , wherein R represents a monosubstituted or disubstituted substituent on the benzene ring, selected from any one or two of hydrogen, phenoxy, phenyl, C1-C4 alkyl, chlorine, and fluorine; The molar ratio of the metal salt to the ethylene structural unit in the polyethylene compound is 0.004-0.012:1, the molar ratio of the nitrosobenzene compound to the ethylene structural unit in the polyethylene compound is 0.10-0.30:1; the molar ratio of the additive to the ethylene structural unit in the polyethylene compound is 0.15-0.17:1; The heating temperature is 70 to 150° C., the irradiation is performed using visible light with a wavelength of 390 to 460 nm, and the stirring reaction time is 2 to 10 hours.

2. The method for synthesizing aminated polyethylene according to claim 1, wherein: The additive further comprises any one of tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylammonium iodide.

3. The method for synthesizing aminated polyethylene according to claim 1, wherein: The polyethylene compound has any molecular weight and is selected from any one or more of low-density polyethylene, high-density polyethylene, linear low-density polyethylene, high-density polyethylene plastic bags, high-density polyethylene plastic bottles, and low-density polyethylene cling film.

4. The method for synthesizing aminated polyethylene according to claim 1, wherein: The magnesium salt is magnesium chloride or magnesium chloride hexahydrate; the iron salt is selected from a trivalent iron salt or a divalent iron salt, the trivalent iron salt is any one of ferric chloride, tetrabutylferric tetrachloride, ferric nitrate nonahydrate, and ferric acetylacetonate; the divalent iron salt is ferrous chloride or ferrous sulfate heptahydrate; the cerium salt is cerium chloride or hydrated cerium chloride; the copper salt is copper chloride or copper trifluoroacetate.

5. The method for synthesizing aminated polyethylene according to claim 1, wherein: The organic solvent is selected from any one of aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, nitro hydrocarbon solvents, ether solvents, and nitrile solvents, wherein the aromatic hydrocarbon solvent is any one of benzene, toluene, trifluorotoluene, and chlorobenzene; the halogenated hydrocarbon solvent is any one of dichloromethane, 1,2-dichloroethane, chloroform, and carbon tetrachloride; the nitro hydrocarbon solvent is any one of nitrobenzene and nitromethane; the ether solvent is any one of tetrahydrofuran, 1,4-dioxane, methyl tert-butyl ether, and diethyl ether; and the nitrile solvent is any one of acetonitrile, benzonitrile, and tert-butyl acetonitrile.

6. The method for synthesizing aminated polyethylene according to claim 1, wherein: The metal salt is ferric chloride or tetrabutylferric tetrachloride; the additive is methylboric acid; and the organic solvent is chlorobenzene or 1,2-dichloroethane.

7. A polyethylene adhesive, characterized in that: The adhesive is an aminated polyethylene obtained by the synthesis method according to any one of claims 1 to 6.

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