Synthetic method of aminated polyethylene

Abstract

The invention discloses a synthesis method of aminated polyethylene, which is characterized in that under the action of cheap metal salt, proper temperature and light energy are provided, and nitrosobenzene compounds are adopted to carry out post-functionalization on carbon-hydrogen bonds of polyethylene compounds, so that catalytic amination functionalization conversion is realized, and the aminated polyethylene is obtained. The method directly utilizes commercialized polyethylene compounds or waste polyethylene plastics to perform carbon-hydrogen bond functionalization, has the advantages of simple reaction, simple operation, short reaction time, mild reaction conditions, high reaction efficiency, easy product separation and purification, good substrate universality and the like, avoids the use of a large amount of precious metals and heavy metal salts, and is suitable for industrial production. The method is very attractive in industrial production, and has very great application potential in the fields of polymer modification, new material synthesis, waste plastic recovery and the like. Meanwhile, the obtained aminated polyethylene has good adhesion strength, the adhesion performance is 5-10 times that of a common polyethylene material, and the aminated polyethylene is suitable for development of a novel plastic adhesive.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer chemical synthesis, and particularly relates to a method for synthesizing aminated polyethylene, which 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 metal salt catalysis under visible light induction. Background Art

[0002] Polyethylene compounds are widely used in food packaging, medical devices, daily necessities and other fields due to their cheapness, availability, excellent physical properties and chemical resistance. They are one of the three major synthetic plastics and play an irreplaceable role in human production and life. The current commercial polyethylene structure is completely composed of inert carbon-carbon bonds and carbon-hydrogen bonds, which makes its adhesion, compatibility, printing and dyeing properties poor, limiting its application in some special fields. At the same time, the large-scale use of polyethylene plastics has also brought serious "white pollution". Recycling and upgrading of waste plastics is of great significance.

[0003] Functionalization of carbon-hydrogen bonds on the polyethylene chain is an important way to change its structure, performance and use, which can achieve the reuse of waste plastics and the re-engineering of their performance, providing a good solution for the sustainable recycling of plastic waste. Among them, the introduction of carbon-nitrogen bonds into the polyolefin backbone can greatly change the viscosity, hydrophilicity, mechanical properties, etc. of polyethylene materials by utilizing the polar effects of heteroatoms and potential hydrogen bonding. However, traditional copolymerization strategies make it difficult to synthesize polyethylene containing nitrogen functional groups, and examples of introducing nitrogen-containing functional groups through post-functionalization strategies are also extremely rare. It is still necessary to develop novel strategies to introduce nitrogen-containing functional groups into polyethylene. 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 carbon-hydrogen bond amination 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. The method has the advantages of mild reaction conditions and simple operation. The method provides a convenient and fast strategy for the preparation of a variety of nitrogen-containing polyethylene compounds. By directly using cheap and abundant polyethylene compounds as raw materials, the use of a large amount 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] In order to achieve the above-mentioned purpose, the present invention adopts a synthesis method of aminated polyethylene by providing temperature and light energy under the action of cheap metal salts, in the presence of additives and aminating reagent nitrosobenzene compounds, in a corresponding organic solvent, to achieve the breaking of carbon-hydrogen bonds in the chain of polyethylene compounds and amination, thereby obtaining polar amine functionalized products. The specific synthesis method is: under the protection of inert gas, polyethylene compounds, nitrosobenzene compounds, metal salts, and additives are added to an organic solvent, and the reaction is stirred under heating and light irradiation to break the carbon-hydrogen bonds in the polyethylene compound chain and amination; after the reaction is complete, stop irradiation, add ethanol to precipitate the solid, filter, wash, and vacuum dry to obtain 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 cling film, 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, tetrabutyl ferric chloride, 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 cupric chloride, cupric trifluoroacetate, etc.

[0010] The above-mentioned additives include any one of organic boron compounds, organic silicon compounds, and organic acid compounds, 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 organic silicon compound is any one of diethylsilane, triethylsilane, and phenylsilane; 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 is benzene, toluene, trifluorotoluene, chlorobenzene, etc.; the halogenated hydrocarbon solvent is dichloromethane, 1,2-dichloroethane, chloroform, carbon tetrachloride, etc.; the ether solvent is tetrahydrofuran, 1,4-dioxane, methyl tert-butyl ether, diethyl ether, etc.; the nitrile solvent is 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, and 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. The present invention provides a one-step efficient amination functionalization method of polyethylene polymer compounds promoted by a cheap metal salt catalyst, and obtains aminated polyethylene materials that are difficult to obtain through traditional copolymerization strategies. The present invention provides a functionalization method for polyethylene waste plastics, which can efficiently and quickly obtain corresponding polyethylene derivatives under the conditions of providing heat energy and light energy, under the action of metal salt catalysts and additives.

[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 expensive metals, and has a wide range of applicability. Low-density polyethylene, high-density polyethylene, linear low-density polyethylene, high-density polyethylene plastic bags, high-density polyethylene plastic bottles, low-density polyethylene cling film, etc. of different molecular weights can be used as substrates, and nitrosobenzene compounds with various electron-withdrawing (fluorine, chlorine, etc.) and electron-donating (methyl, phenoxy, etc.) groups can be used as amine sources, and polyethylene compounds with different structural aminations can be quickly and simply synthesized.

[0020] 3. 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, and is suitable for recycling waste plastics and developing new plastic adhesives. At the same time, the aminated polyethylene product can also be further derived to prepare other amine-containing polyethylene materials. The method of the present invention 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 embodiments 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 without conflict. The following embodiments are helpful to understand 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 2mmol) with a number average molecular weight of 2.1kDa, nitrosobenzene (x mmol), additive 1 (0.30mmol) were added to a 25mL dry reaction tube in sequence, and metal salt (y mmol), additive 2 (y mmol), and organic solvent (3.0mL) 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, and 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, 10mL of ethanol was added to precipitate the solid, stirred at room temperature for 5 to 10 minutes, filtered, and washed alternately with 10mL of dichloromethane and 10mL of ethanol for 3 times until the small molecules were completely removed, and vacuum dried to obtain the target product, aminated polyethylene.

[0025]

[0026] Table 1

[0027]

[0028]

[0029]

[0030] Embodiments 18 to 32

[0031] According to the raw material ratio and reaction conditions in Table 2, polyethylene compounds (ethylene structural unit 2mmol), nitrosobenzene compounds (x mmol), and methylboric acid (0.30mmol) were added to a 25mL dry reaction tube in sequence, and tetrabutylferric tetrachloride (y mmol) and chlorobenzene (3.0mL) 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 to dissolve, and after the reactants were completely dissolved, they were irradiated under visible light with a wavelength of 425nm and stirred continuously. After the reaction for 2 hours, the reaction tube was removed from the light source, 10mL of ethanol was added to precipitate the solid, stirred at room temperature for 5 to 10 minutes, filtered, and washed alternately with 10mL of dichloromethane and 10mL of ethanol for 3 times until the small molecules were completely removed, and vacuum dried to obtain the target product, aminated polyethylene.

[0032]

[0033] Table 2

[0034]

[0035]

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

[0037] It can be seen from the above embodiments and experimental results that the present invention can achieve functionalization of polyethylene compounds and their corresponding waste plastics under visible light irradiation and cheap 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 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(pinacol)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, p-toluenesulfonic acid, and cyclohexylcarboxylic acid.

2. The method for synthesizing aminated polyethylene according to claim 1, characterized in that: 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, characterized in that: 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, characterized in that: The nitrosobenzene compound is Wherein R represents a mono- or di-substituted substituent on the benzene ring, selected from any one or two of hydrogen, phenoxy, phenyl, C1-C4 alkyl, chlorine and fluorine.

5. The method for synthesizing aminated polyethylene according to claim 1, characterized in that: 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, tetrabutyl ferric chloride, 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.

6. The method for synthesizing aminated polyethylene according to claim 1, characterized in that: 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; and the molar ratio of the additive to the ethylene structural unit in the polyethylene compound is 0.15-0.17:

1.

7. The method for synthesizing aminated polyethylene according to claim 1, characterized in that: 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.

8. The method for synthesizing aminated polyethylene according to claim 1, characterized in that: The heating temperature is 70-150° C., the irradiation is performed using visible light with a wavelength of 390-460 nm, and the stirring reaction time is 2-10 hours.

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

10. 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 9.

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