Heterogeneous photocatalyst and method of making and using same

Abstract

The present disclosure provides a heterogeneous photocatalyst, a preparation method and application thereof. The heterogeneous photocatalyst comprises a nano semiconductor with photocatalytic performance, polyolefin acid particles and an alpha-diazo nickel metal catalyst. The polyolefin acid particles are formed with the nano semiconductor as a condensation nucleus to form a catalytically active layer on the surface thereof, and the alpha-diazo nickel metal catalyst is loaded by using the carboxyl-metal ion dynamic crosslinking point contained in the polyolefin acid particles. The present disclosure also provides a preparation method of the heterogeneous photocatalyst, comprising: dissolving and uniformly mixing the nano semiconductor and alkyl aluminum protected olefin acid monomers at a first reaction temperature, and then adding a cocatalyst and an alpha-diazo nickel metal catalyst; allowing the polymerization reaction of the olefin acid monomers to occur at a second reaction temperature, and forming a polyolefin acid catalytically active layer on the surface of the nano semiconductor after heterogeneous nucleation, and then cooling to a third reaction temperature after standing or stirring for a period of time to obtain the heterogeneous photocatalyst.

Description

Technical Field

[0001] This disclosure relates to the fields of catalytic olefin polymerization and photodegradation of polyethylene, specifically to a heterogeneous photodegradation catalyst, photodegradation of functionalized polyethylene, its preparation method and application; more specifically to a heterogeneous photodegradation catalyst, and a method for preparing visible light-degradable functionalized polyethylene using the heterogeneous photodegradation catalyst. Background Technology

[0002] Waste plastics cause serious environmental pollution, and polyolefins are the main material used in plastic products. Polyolefins are primarily composed of carbon and hydrogen atoms, with molecular weights generally exceeding 100,000, making them difficult to self-degrade or be broken down by microorganisms. Current disposal methods mainly involve landfilling or incineration, which not only harms soil organisms and occupies land resources but also pollutes the atmosphere. Therefore, there is an urgent need to find a more economical and environmentally friendly method to degrade plastic products.

[0003] Studies have shown that fungi, bacteria, and other microorganisms that can grow on plastic products can use carbon as an energy source to biodegrade plastics. However, this method has many limitations: for example, the high molecular weight of polymers makes biodegradation difficult. Generally, these polymers need to be pretreated under ultraviolet radiation through thermal oxidation or the addition of oxidizing agents to break them down into smaller molecular structures, which has a synergistic effect on biodegradation and is beneficial to it; however, this treatment method is costly.

[0004] Nanoscale semiconductor materials such as titanium dioxide possess the ability to absorb energy and generate electrons and holes, promoting the formation of free radicals and thus facilitating the oxidative degradation of the polymer matrix. This can serve as an environmentally friendly method for treating plastic products. Semiconductor / polyethylene composites, as a novel functional composite material, are typically obtained by in-situ mixing of photodegradation catalysts and polyethylene materials, or by melt blending. The photodegradation catalyst in the semiconductor / polyethylene composite enters an excited state under light or heat conditions, causing the polymer chains to oxidize and break down into smaller molecular weight segments, ultimately becoming small molecules that can be decomposed by microorganisms. However, due to the very small particle size of semiconductor materials, typically nanoscale, they are extremely prone to agglomeration. Therefore, melt blending makes it difficult to disperse them uniformly within the composite matrix, thus affecting the synthesis and degradation of photodegradable polyethylene.

[0005] In conclusion, the search for an economical, efficient, green, and environmentally friendly photodegradable polyethylene composite material is of profound significance. Summary of the Invention

[0006] In view of this, in order to obtain a functionalized polyethylene composite material with high composite strength, uniform distribution of nano-semiconductor materials, and photodegradability, this disclosure proposes a heterogeneous photodegradation catalyst, its preparation method, and its application, in order to at least partially solve the above-mentioned technical problems.

[0007] To address the aforementioned technical problems, this disclosure proposes a heterogeneous photodegradation catalyst, comprising:

[0008] Nano-semiconductors possess photocatalytic properties;

[0009] Polyacrylic acid particles are formed using nano-semiconductors as condensation nuclei, and a catalytically active layer is formed on their surface; and

[0010] An α-diimine nickel metal catalyst adsorbed on polyacrylic acid particles, wherein the polyacrylic acid particles contain dynamic crosslinking points of carboxyl-metal ions to achieve the loading of the α-diimine nickel metal catalyst.

[0011] According to embodiments of this disclosure, the nano-semiconductor includes at least one of titanium dioxide, cuprous oxide, nano-iron stearate, and titanium dioxide / cuprous oxide heterojunction.

[0012] According to embodiments of this disclosure, the particle size of the nano-semiconductor is 5-100 nm.

[0013] Another aspect of this disclosure provides a method for preparing a heterogeneous photodegradation catalyst, comprising:

[0014] At the first reaction temperature, after dissolving and uniformly mixing the nano-semiconductor and the alkylaluminum-protected olefin monomer, a co-catalyst and an α-diimine nickel metal catalyst are added.

[0015] The polymerization reaction of olefin monomers occurs at the second reaction temperature. After heterogeneous nucleation, a polyolefin catalytic active layer is formed on the surface of the nano-semiconductor. After standing or stirring for a period of time, it is cooled to the third reaction temperature to obtain a heterogeneous photodegradation catalyst.

[0016] According to embodiments of this disclosure, the mass ratio of alkylaluminum-protected olefin monomer to nano-semiconductor is 1:0.1-50.

[0017] According to embodiments of this disclosure, the molar ratio of the α-diimine nickel metal catalyst to the alkylaluminum protected olefin monomer is 1:50-5000.

[0018] According to embodiments of this disclosure, the acrylate monomer includes at least one of the following:

[0019] 10-Undecenoic acid, 5-hexenoic acid, 4-pentenoic acid, trans-oleic acid, acrylic acid, 5-norbornene-2-carboxylic acid.

[0020] According to embodiments of this disclosure, the molar ratio of the co-catalyst to the α-diimine nickel metal catalyst is 1:100 to 5000.

[0021] According to embodiments of this disclosure, the cocatalyst includes one or more of diethylaluminum chloride, methylaluminoxane, ethylaluminum dichloride, triisobutylaluminum, and tris(pentafluorophenyl)boron.

[0022] According to an embodiment of this disclosure, the first temperature range is 0 to 50°C.

[0023] According to an embodiment of this disclosure, the second temperature range is -30 to 50°C.

[0024] According to embodiments of this disclosure, the third temperature range is -80 to 15°C.

[0025] According to embodiments of this disclosure, the settling or stirring time is 4-12 hours.

[0026] Another aspect of this disclosure provides a method for preparing a photodegradable functionalized polyethylene composite material, comprising:

[0027] A heterogeneous photodegradation catalyst was used to induce homopolymerization of ethylene monomers in an organic solvent to prepare a photodegradable polyethylene composite material. The polyacrylic acid catalytic active layer served as a coupling agent to combine polyethylene and nano-semiconductors.

[0028] According to embodiments of this disclosure, in the homopolymerization reaction, the partial pressure of ethylene gas is 1-40 atmospheres, the homopolymerization reaction time is 2 min to 8 h, and the homopolymerization reaction temperature is -30 to 80°C.

[0029] According to embodiments of this disclosure, the organic solvent includes at least one of the following:

[0030] Petroleum ether, pentane, hexane, heptane, octane, hydrogenated gasoline, methylcyclohexane, decahydronaphthalene, methylcyclohexane, cyclohexane, benzene, toluene, xylene, hydrogenated gasoline, dichloromethane, chloroform, chlorobenzene, and dichlorobenzene.

[0031] The heterogeneous photodegradation catalyst and its preparation method, as well as the method for preparing functionalized polyethylene composite materials disclosed herein, have one or more of the following beneficial effects:

[0032] (1) According to the embodiments of this disclosure, the small size and low surface energy of the nano-photodegradation catalyst can be used as a condensation nucleus in the polymerization process of preparing heterogeneous photodegradation catalyst, so that polyacrylic acid particles form a catalytic active layer on its surface. The carboxyl-metal ion dynamic bond crosslinking points contained in the polyacrylic acid particles in the catalytic active layer can realize the loading of α-diimine nickel metal catalyst, thereby obtaining a heterogeneous photodegradation catalyst. The polyacrylic acid catalytic active layer can also be used as a coupling agent to enhance the organic compatibility of nano-semiconductors.

[0033] Alkyl aluminum-protected olefin monomers undergo precipitation polymerization under the catalysis of α-diimine nickel catalyst, producing polymer particles. After the polymerization reaction is complete, the α-diimine nickel catalyst in the system hardly undergoes deactivation, but is instead adsorbed by the newly generated polyaluminum olefin salt particles, thus obtaining catalytically active composite particles.

[0034] (2) According to the embodiments of this disclosure, on the one hand, the heterogeneous photodegradation catalyst prepared in this disclosure is a polymer particle that is insoluble in organic solvents. In the ethylene polymerization reaction, the heterogeneous photodegradation catalyst is used as a condensation nucleus for the ethylene polymerization reaction, so that the ethylene polymer preferentially settles on the condensation nucleus to form solid particulate polyethylene material, thereby reducing the viscosity of the reaction system and improving the efficiency of ethylene monomer conversion to polyethylene composite material; on the other hand, in the ethylene polymerization reaction, the heterogeneous photodegradation catalyst effectively avoids the problems of uneven stirring, system exothermic reaction and other reasons caused by high viscosity during homogeneous polymerization, which reduce the catalytic efficiency of polyethylene synthesis and polymer scaling in the reactor, thereby achieving higher ethylene monomer polymerization activity than homogeneous polymerization.

[0035] (3) According to the embodiments of this disclosure, nano-semiconductor materials are used as condensation nuclei to uniformly disperse ethylene on their surface; simultaneously, α-diimine nickel metal catalysts in heterogeneous photodegradation catalysts are used to catalyze the in-situ conversion of ethylene to polyethylene, thereby preparing a functionalized polyethylene composite material with photodegradability. Compared with melt blending, in-situ polymerization results in a more uniform distribution of nano-semiconductor materials, effectively enhancing the mechanical properties of polyethylene materials. In the degradation of polyethylene composite materials, the nano-semiconductor catalyst can also be used as a photodegrading agent, absorbing energy under light to generate electrons and holes, promoting the formation of free radicals in the nano-semiconductor. The strong oxidizing properties of these free radicals can oxidize and decompose polyethylene into polymers with smaller molecular weights, thus achieving the photodegradation of polyethylene. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the preparation of the heterogeneous photodegradation catalyst and its application in olefin polymerization in this disclosure;

[0037] Figure 2This is a scanning electron microscope image of the titanium dioxide-supported heterogeneous photodegradation catalyst prepared in Example 1 of this disclosure;

[0038] Figure 3 This is the elemental energy spectrum of titanium dioxide prepared in Example 1 of this disclosure;

[0039] Figure 4 This is the elemental energy spectrum of the heterogeneous photodegradation catalyst supported on titanium dioxide in Example 1 of this disclosure;

[0040] Figure 5 This is a scanning electron microscope image of the heterogeneous photodegradation catalyst supported on a nano-heterojunction in Example 2 of this disclosure;

[0041] Figure 6 The stress-strain curves are those of the nano-titanium dioxide-polyethylene composite material prepared in Application Example 1 of this disclosure and the titanium dioxide composite material prepared by melt blending in Comparative Example 1.

[0042] Figure 7 The curves showing the number-average molecular weight and light exposure time, as well as the changes in molecular weight distribution and light exposure time of the nano-titanium dioxide-polyethylene composite material prepared in Application Example 1 of this disclosure are shown.

[0043] Figure 8 The stress-strain curves are those of the nano-heterojunction-polyethylene composite material prepared in Application Example 2 of this disclosure and the nano-heterojunction-polyethylene composite material prepared by melt blending in Comparative Example 2.

[0044] Figure 9 This is a comparison of the photodegradation effects of the nano-heterojunction-polyethylene composite material prepared in Application Example 2 of this disclosure and the nano-heterojunction-polyethylene composite material prepared by melt blending in Comparative Example 2. Detailed Implementation

[0045] To make the objectives, technical solutions and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0046] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this disclosure.

[0047] In the process of realizing this disclosure, it was found that melt blending method is difficult to uniformly mix nano-semiconductor materials and polymer materials and the compatibility between the two is poor, resulting in poor mechanical properties and yield of the prepared polymer materials. At the same time, it is easy to cause scaling in the reactor during the preparation process.

[0048] To address the aforementioned technical problems, this disclosure proposes a heterogeneous photodegradation catalyst, comprising:

[0049] Nano-semiconductors possess photocatalytic properties; polyacrylic acid particles are formed using nano-semiconductors as condensation nuclei, with a catalytically active layer and an α-diimine nickel metal catalyst adsorbed on their surface. The polyacrylic acid particles contain dynamic cross-linking points between carboxyl groups and metal ions to achieve the loading of the α-diimine nickel metal catalyst.

[0050] According to embodiments of this disclosure, the small size and low surface energy of the nano-photodegradation catalyst can be used as a condensation nucleus in the polymerization process of the heterogeneous photodegradation catalyst, so that polyacrylate particles can form a catalytic active layer on its surface. The polymer particles formed by the polyacrylate particles in the catalytic active layer contain carboxyl-metal ion dynamic bond crosslinking points, which can realize the loading of α-diimine nickel metal catalyst, thereby obtaining a heterogeneous photodegradation catalyst.

[0051] According to embodiments of this disclosure, the nano-semiconductor includes at least one of titanium dioxide, cuprous oxide, and nano-ferric stearate.

[0052] According to embodiments of this disclosure, the nano-semiconductor can also be selected as a nano-titanium dioxide / nano-cuprous oxide heterojunction.

[0053] According to embodiments of this disclosure, the crystal form of nano-titanium dioxide includes one or more of anatase and anatase-gold red mixed types.

[0054] According to embodiments of this disclosure, the particle size of the nano-semiconductor is 5-100 nm, wherein it can be selected as 10 nm, 25 nm, 50 nm, 80 nm, etc.

[0055] According to embodiments of this disclosure, the nano-semiconductor is preferably selected from materials with good photocatalytic performance. Under illumination, the nano-semiconductor absorbs energy to generate electrons and holes, promoting the formation of free radicals, thereby oxidatively degrading the polymer. The small size and low surface energy of the nano-semiconductor material allow it to serve as condensation nuclei in the polymerization process of olefin monomers. Furthermore, polyolefin particles containing dynamic crosslinking points of carboxyl-metal ions are constructed on the surface of the nano-semiconductor, thereby achieving the loading of α-diimine nickel and obtaining a heterogeneous photodegradation catalyst.

[0056] Figure 1 The preparation of the heterogeneous photodegradation catalyst of this disclosure and its method for preparing photodegradable functionalized polyethylene are illustrated schematically.

[0057] Another aspect of this disclosure provides a method for preparing heterogeneous photodegradation catalysts, such as... Figure 1 As shown, it includes:

[0058] At the first reaction temperature, after dissolving and uniformly mixing the nano-semiconductor and the alkylaluminum-protected olefin monomer, a co-catalyst and an α-diimine nickel metal catalyst are added.

[0059] The polymerization reaction of olefin monomers occurs at the second reaction temperature. After heterogeneous nucleation, a polyolefin catalytic active layer is formed on the surface of the nano-semiconductor. After standing or stirring for a period of time, it is cooled to the third reaction temperature to obtain a heterogeneous photodegradation catalyst.

[0060] According to embodiments of this disclosure, an α-diimine nickel metal catalyst can catalyze the precipitation homopolymerization reaction of olefin monomers. The amphiphilic nature of the alkylaluminum-protected polar olefin monomers and the interaction between the -COOAl groups in the olefin monomers and the surface of the nano-semiconductor material are utilized. Therefore, in the presence of the nano-semiconductor material, the polymerization reaction of the alkylaluminum-protected polar olefin monomers is catalyzed by the α-diimine nickel metal catalyst. The resulting polyolefin particles use the nano-semiconductor material as condensation nuclei, forming a catalytically active layer on its surface. Furthermore, after the polyolefin polymerization reaction is complete, the α-diimine nickel catalyst in the system can be adsorbed by the newly generated polyolefin particles due to the presence of carboxyl-metal ion dynamic crosslinking points in the polyolefin particles. This results in almost no deactivation of the α-diimine nickel metal catalyst, thereby obtaining a heterogeneous photodegradation catalyst with catalytic activity.

[0061] According to embodiments of this disclosure, the mass ratio of alkylaluminum-protected olefin monomer to nano-semiconductor is 1:0.1-50, wherein the mass ratio of alkylaluminum-protected olefin monomer to nano-semiconductor can be selected as 1:1, 1:20, 1:35, 1:50, etc.

[0062] According to embodiments of this disclosure, the molar ratio of the α-diimine nickel metal catalyst to the alkylaluminum protected olefin monomer is 1:50-5000, wherein it can be selected as 1:50, 1:500, 1:2000, 1:4000, etc.

[0063] According to embodiments of this disclosure, the molar ratio of the α-diimine nickel metal catalyst to the alkylaluminum protected olefin monomer can be from 1:10 to 10000, more preferably from 1:10 to 100. Within this molar ratio range, a high-performance supported heterogeneous photodegradation catalyst can be obtained without deactivation of the α-diimine nickel metal catalyst.

[0064] According to embodiments of this disclosure, the acrylate monomer includes at least one of the following:

[0065] 10-Undecenoic acid, 5-hexenoic acid, 4-pentenoic acid, trans-oleic acid, acrylic acid, 5-norbornene-2-carboxylic acid.

[0066] According to embodiments of this disclosure, the alkyl-protected olefin monomer includes at least one of the following:

[0067] Di(10-undecenoic acid) aluminum chloride, di(5-hexenoic acid) aluminum chloride, di(4-pentenoic acid) aluminum chloride, di(trans-oleic acid) aluminum chloride, di(acrylic acid) aluminum chloride, di(5-norbornene-2-carboxylic acid) aluminum chloride.

[0068] According to embodiments of this disclosure, the α-diimine nickel metal catalyst preferentially coordinates with the polar bonds of the olefin monomer to reduce the reactivity of subsequent ethylene polymerization. The olefin monomer protected by alkylaluminum can protect the polar sites, which is beneficial for inserting ethylene into the heterogeneous photodegradation catalyst during the ethylene polymerization reaction.

[0069] According to embodiments of this disclosure, the molar ratio of the co-catalyst to the α-diimine nickel metal catalyst is 1:100 to 5000, wherein the molar ratio of the co-catalyst to the α-diimine nickel metal catalyst can be selected as 1:100, 1:500, 1:1000, 1:5000, etc.

[0070] According to embodiments of this disclosure, the cocatalyst includes one or more of diethylaluminum chloride, methylaluminoxane, ethylaluminum dichloride, triisobutylaluminum, and tris(pentafluorophenyl)boron.

[0071] According to embodiments of this disclosure, the main function of the co-catalyst is to activate the α-diimine nickel metal catalyst.

[0072] According to embodiments of this disclosure, the α-diimine nickel metal catalyst exhibits low activity and slow reaction rate at low temperatures, and is prone to deactivation at high temperatures. Therefore, in embodiments of this disclosure, the first temperature range is 0–50°C, wherein 10°C, 20°C, 40°C, 50°C, etc., are optional.

[0073] According to embodiments of this disclosure, the second temperature range is -30 to 50°C, wherein it can be selected as -30°C, 0°C, 10°C, 30°C, etc.

[0074] According to embodiments of this disclosure, the third temperature range is -80 to 15°C, wherein it can be selected as -80°C, -50°C, -10°C, 10°C, etc.

[0075] According to embodiments of this disclosure, the settling or stirring time is 4-12 hours, wherein 4 hours, 6 hours, 8 hours, 10 hours, etc. can be selected.

[0076] Continue as Figure 1 As shown, another aspect of this disclosure provides a method for preparing a photodegradable functionalized polyethylene composite material, comprising:

[0077] A photodegradable polyethylene composite material was prepared by using a heterogeneous photodegradation catalyst to induce homopolymerization of ethylene monomers in an organic solvent.

[0078] According to embodiments of this disclosure, a polyacrylate catalytic active layer serves as a coupling agent to combine polyethylene and nano-semiconductors.

[0079] According to embodiments of this disclosure, on one hand, the heterogeneous photodegradation catalyst is a polymer particle insoluble in organic solvents. During the ethylene polymerization reaction, the heterogeneous photodegradation catalyst can act as a condensation nucleus. The ethylene polymer preferentially settles on the condensation nucleus and forms solid particulate polyethylene material under the catalysis of the α-diimine nickel metal catalyst, thereby reducing the viscosity of the reaction system and improving the mass transfer efficiency of ethylene monomers. This effectively avoids problems such as reduced catalytic efficiency and polymer scaling in the reactor caused by high viscosity and exothermic system in traditional homopolymerization reactions, thereby achieving higher ethylene polymerization activity than homogeneous polymerization with α-diimine nickel metal catalyst. Furthermore, compared with homogeneous copolymerization / modification methods, the resulting heterogeneous photodegradation catalyst containing α-diimine nickel metal catalyst has the advantage of converting all alkylaluminum-protected olefin monomers into polyolefin particles during the synthesis process, thereby improving the polymerization activity of α-diimine nickel metal catalyst for ethylene. At the same time, the polyolefin catalytic active layer in the heterogeneous photodegradation catalyst can act as a coupling agent, which can enhance the composite strength of nano-semiconductors and polyethylene and the uniformity of nano-semiconductor distribution, thereby improving the photodegradation performance of nano-semiconductors in the photocatalytic degradation of polyethylene.

[0080] According to embodiments of this disclosure, in the homopolymerization reaction, the partial pressure of ethylene gas is 1-40 atmospheres, wherein the partial pressure of ethylene gas can be selected as 10 atmospheres, 20 atmospheres, 30 atmospheres, 40 atmospheres, etc.

[0081] According to embodiments of this disclosure, the homopolymerization reaction time is 2 min to 8 h, wherein the homopolymerization reaction time can be selected as 10 min, 1 h, 5 h, 8 h, etc.

[0082] According to embodiments of this disclosure, the homopolymerization reaction temperature is -30 to 80°C, wherein the homopolymerization reaction temperature can be selected from -30°C, -10°C, 0°C, 20°C, etc.

[0083] According to embodiments of this disclosure, the organic solvent includes at least one of the following:

[0084] Petroleum ether, pentane, hexane, heptane, octane, hydrogenated gasoline, methylcyclohexane, decahydronaphthalene, methylcyclohexane, cyclohexane, benzene, toluene, xylene, hydrogenated gasoline, dichloromethane, chloroform, chlorobenzene, and dichlorobenzene.

[0085] According to embodiments of this disclosure, in the homopolymerization reaction, the mass concentration of the heterogeneous photodegradation catalyst in the organic solvent is 0.01-200 g / L.

[0086] According to embodiments of this disclosure, the same organic solvent can be used to prepare heterogeneous photodegradation catalysts and to prepare functionalized polyethylene composite materials with photodegradation capabilities.

[0087] It should be noted that the described embodiments are merely some, not all, of the embodiments disclosed herein. Other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are all within the scope of protection of this disclosure.

[0088] It should be noted that, unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person with ordinary skill in the art to which this application pertains. Where the terms "first," "second," etc., are used throughout, they are used only to distinguish similar objects and should not be construed as indicating or implying their relative importance, order of precedence, or implicitly specifying the number of technical features indicated. It should be understood that the data in the descriptions of "first," "second," etc., can be interchanged where appropriate.

[0089] According to embodiments of this disclosure, the α-diimine nickel metal catalyst can be any α-diimine nickel metal catalyst known in the art, and can be commercially available or conveniently prepared by methods known in the art.

[0090] According to embodiments of this disclosure, nano-semiconductor materials can be readily prepared either commercially available or by methods known in the art.

[0091] According to embodiments of this disclosure, the cocatalyst may be one or more of diethylaluminum chloride, methylaluminoxane, ethylaluminum dichloride, triisobutylaluminum and tris(pentafluorophenyl)boron, which are commercially available or conveniently prepared by methods known in the art.

[0092] According to embodiments of this disclosure, there are no particular limitations on the reaction vessel; for example, an autoclave equipped with a magnetic stirrer can be used.

[0093] According to embodiments of this disclosure, the polymerization process is carried out under anhydrous and oxygen-free conditions, all sensitive substances are stored in a dry glove box, all solvents are strictly dried and dehydrated, ethylene gas is purified by passing it through a dehydration and deoxygenation column, and other polymerizable monomers are purified by dehydration, deoxygenation, and vacuum distillation.

[0094] According to the embodiments of this disclosure, all raw materials and reagents used are commercially available, and all raw materials and reagents are used directly after simple dehydration and deoxygenation as needed after purchase.

[0095] According to embodiments of this disclosure, nuclear magnetic resonance spectroscopy was performed using a Bruker 400MHz NMR instrument, molecular weight and molecular weight distribution were determined by high-temperature GPC, polymer melting point was determined by differential scanning calorimetry (DSC), morphology of the supported catalyst and polyethylene composite material was tested by scanning electron microscopy (SEM), and the mechanical properties of the polymer were tested by a universal tensile testing machine.

[0096] Preparation Example 1: The specific process for preparing a heterogeneous photodegradation catalyst by using nano-titanium dioxide as the nano-semiconductor material and supporting an α-diimine nickel photodegradation catalyst is as follows:

[0097] At room temperature, under magnetic stirring at 1500 rpm, 0.216 g (1 mmol) of bis(10-undecenoic acid) aluminum chloride was added to a 20 mL glass reaction flask, followed by 8.5 mL of n-heptane to dissolve it. Then, 0.8 g of nano-titanium dioxide (particle size 25 nm) was added, and the mixture was stirred for 1 h to ensure uniform dispersion of the nano-titanium dioxide in the n-heptane. Next, 0.8 mmol of diethylaluminum chloride and 1.4 μmol of α-diimine nickel metal catalyst (Ni1) as shown below were added. The reaction mixture was stirred at 25 °C for 8 h, and the resulting reaction mixture dispersion was cooled to -20 °C for storage, yielding a heterogeneous photodegradation catalyst dispersion prepared from nano-titanium dioxide supported on the α-diimine nickel catalyst. This dispersion can be directly used in subsequent ethylene homopolymerization reactions without purification or other treatment.

[0098]

[0099] The α-diimine nickel metal catalyst (Ni1) was prepared as follows: 16.5 mmol of acenaphthoquinone was dispersed in 100 mL of acetonitrile solution to form a suspension. The mixture was refluxed at 80 °C for 60 minutes, then 30 mL of acetic acid was added, and the mixture was heated further until the acenaphthoquinone dissolved. 2,6-Diisopropylphenylaniline, 92% (16.0 g, 89.9 mmol), was added to the hot solution using a dropping funnel over 20 minutes, and the resulting solution was heated again under reflux for 5 hours. The resulting solution was cooled to room temperature, and the precipitate was filtered to obtain an orange-yellow solid. The orange-yellow solid was washed with pentane (3 × 20 mL) and dried in air to obtain an orange-red solid. Under a nitrogen atmosphere, [(1,2-dimethoxyethane)NiBr2] (0.16 g, 0.50 mmol) and bis[N,N′-(2,6-diisopropylphenyl)imino]acenaphthene (0.50 mmol) were placed in a Schlenk flask, and 20 mL of CH2Cl2 was added to the reaction mixture. The reaction mixture was stirred at room temperature for 24 hours. The resulting suspension was filtered, and the solvent was removed under vacuum. The residue was washed with diethyl ether (3 × 15 mL) and dried under vacuum at room temperature to obtain the α-diimine nickel metal catalyst (Ni1) (for a more detailed method for preparing the α-diimine nickel metal catalyst, refer to: Polymer 2017, 127, 88-100).

[0100] The obtained nano-titanium dioxide supported heterogeneous photodegradation catalyst (Preparation Example 1) was characterized by scanning electron microscopy.

[0101] Figure 2 The illustration shows that in the heterogeneous photodegradation catalyst prepared in Example 1, polyolefin acid forms a thin catalytically active layer on the surface of titanium dioxide, and the polyolefin acid does not exhibit agglomeration or homogeneous nucleation.

[0102] Figure 3 The elemental energy spectrum of nano-titanium dioxide is schematically shown; Figure 4 The elemental energy spectrum of the heterogeneous photodegradation catalyst prepared by supporting α-diimine nickel photodegradation catalyst with nano-titanium dioxide is schematically shown (i.e., after polymerization of alkylaluminum protected olefin monomers).

[0103] from Figure 3 and Figure 4 The comparison shows that after polyacrylic acid polymerizes on the surface of the nano-semiconductor, the elemental energy spectrum shows a distinct Al elemental characteristic peak, indicating that polyacrylic acid uses the nano-semiconductor material as a condensation nucleus to form a catalytically active layer on its surface. Figure 4 ), while those without polymerized polyolefin acid on the nano-semiconductor surface lack Al element. Preparation Example 2: The specific process for preparing heterogeneous photodegradation catalysts using nano-heterojunction-supported α-diimine nickel photodegradation catalysts is as follows:

[0104] At room temperature, with magnetic stirring at 1500 r / min, 0.216 g (1 mmol) of bis(10-undecenoic acid) aluminum chloride was added to a 20 mL glass reaction flask, followed by 8.5 mL of n-heptane to dissolve it. 0.08 g of a heterojunction of nano-titanium dioxide (5 nm particle size) and cuprous oxide was added (the preparation method of this semiconductor heterojunction is described in reference: Catalysis Communications, 2009, 10(14), 1839-1843), and the mixture was stirred for 1 h to uniformly disperse the nano-titanium dioxide and cuprous oxide heterojunction in n-heptane. Then, 0.8 mmol of diethylaluminum chloride and 1.4 μmol of α-diimine nickel metal catalyst (Ni1) as described in Preparation Example 1 were added. The reaction mixture was stirred at 25°C for 8 hours. The resulting reaction mixture dispersion was then cooled to -20°C and stored to obtain a heterogeneous photodegradation catalyst dispersion prepared by supporting α-diimine nickel catalyst with nano-heterojunction. This dispersion can be directly used in the subsequent ethylene homopolymerization reaction without purification or other treatment.

[0105] The preparation method of the α-diimine nickel metal catalyst (Ni1) in Preparation Example 2 is the same as that in Preparation Example 1.

[0106] Figure 5 The image shows a schematic scanning electron microscope (SEM) image of the heterogeneous photodegradation catalyst prepared by supporting an α-diimine nickel photodegradation catalyst with a nano-heterojunction.

[0107] like Figure 5 As shown, the Ti and Cu spectra indicate that titanium dioxide and cuprous oxide are uniformly distributed in the nano-heterojunction.

[0108] Application Example 1: A heterogeneous photodegradation catalyst prepared using α-diimine nickel catalyst supported on nano-titanium dioxide was used to catalyze ethylene polymerization and prepare a nano-titanium dioxide polyethylene composite material with photodegradation properties (the polyethylene composite material is denoted as "Ni@titanium dioxide"). The specific preparation process is as follows:

[0109] In a nitrogen-filled glove box, 85 mL of heptane was added to a 300 mL high-pressure glass reactor, followed by 10 mL of the heterogeneous photodegradation catalyst dispersion prepared in Preparation Example 1 (based on Ni, the amount was 1.4 μmol Ni). The high-pressure glass reactor was connected to a high-pressure pipeline and evacuated, then connected to an ethylene gas cylinder, filled with ethylene gas, and the pressure was adjusted to 8 atmospheres. The polymerization reaction was carried out at room temperature for 30 minutes. Then, the system was cooled in a water bath to maintain a stable temperature of 20 °C. The reaction was stopped, the reactor was opened, the product was transferred out, filtered under reduced pressure, washed with 0.5 L of ethanol, and then transferred to a vacuum drying oven to dry, yielding a white polymer powder.

[0110] Tests showed that the nano-titanium dioxide polyethylene composite material had a number-average molecular weight of 101,000, a melting point of 116℃, a mass of 12.9 grams, a tensile strength of 39±3 MPa, and an elongation at break of 620±20%. Figure 6 ).

[0111] Application Example 2: A heterogeneous photodegradation catalyst prepared using α-diimine nickel photodegradation catalyst supported on a nano-heterojunction was used to catalyze the polymerization of ethylene to prepare a nano-heterojunction polyethylene composite material with photodegradation properties (the polyethylene composite material is denoted as "Ni@heterojunction").

[0112] In a nitrogen-filled glove box, 85 mL of heptane was added to a 300 mL high-pressure glass reactor, followed by 10 mL of the nano-heterojunction supported heterogeneous catalyst dispersion prepared in Preparation Example 2 (the amount, based on Ni, was 1.4 μmol Ni). The high-pressure glass reactor was connected to a high-pressure pipeline and evacuated, then connected to an ethylene gas cylinder. After purging with ethylene gas and adjusting the pressure to 8 atmospheres, polymerization was carried out at room temperature for 30 minutes. The reactor was then cooled in a water bath to maintain a stable temperature of 20°C. The reaction was stopped, the reactor was opened, the product was transferred, filtered under reduced pressure, washed with 0.5 L of ethanol, and then dried in a vacuum drying oven to obtain a white polymer.

[0113] Tests showed that the number-average molecular weight of the nano-heterojunction polyethylene composite material was 290,000, the melting point was 108℃, the mass was 8.3 grams, the tensile strength was 45±2 MPa, and the elongation at break was 800±20%. Figure 8 ).

[0114] Comparative Example 1: The use of melt blending in the preparation and material properties of nano-titanium dioxide-polyethylene composite materials (denoted as "LDPE-titanium dioxide") is as follows:

[0115] 9.2g of LDPE (Maoming Petrochemical, 951-050), 0.8g of titanium dioxide (particle size 25nm), and 0.1g of BHT (butylated hydroxytoluene antioxidant) were melt-blended and then extruded using a twin-screw extrusion mechanism to obtain nano-titanium dioxide (20%)-polyethylene composite material.

[0116] Figure 6 The stress-strain curves of the nano-titanium dioxide polyethylene composite material (Ni@titanium dioxide) prepared in Application Example 1 of this disclosure and the nano-titanium dioxide-polyethylene composite material (LDPE-titanium dioxide) prepared by melt blending are illustrated schematically.

[0117] like Figure 6As shown, the tensile strength of the nano-titanium dioxide polyethylene composite material prepared by melt blending in Comparative Example 1 is 7.1 MPa, and the elongation at break is 73%; while the tensile strength of the nano-titanium dioxide polyethylene composite material prepared in Application Example 1 is 39±3 MPa, and the elongation at break is 620±20%. This shows that the mechanical properties of the nano-titanium dioxide polyethylene composite material prepared by the method provided in this disclosure (Application Example 1) are better than those of the nano-titanium dioxide polyethylene composite material prepared by melt blending (Comparative Example 1).

[0118] In addition, photodegradation tests were conducted on polyethylene in Example 1 and polyethylene in Comparative Example 1. The specific test procedures are as follows:

[0119] Before the experiment, titanium dioxide polyethylene composite films were prepared into 20×10×0.5mm thin film samples. Then, photodegradation experiments were conducted on the titanium dioxide polyethylene composites prepared by both methods using a 365nm UV lamp. Samples were taken at regular intervals, and the degree of polymer degradation was determined using molecular weight analysis.

[0120] Figure 7 The diagram schematically illustrates the number-average molecular weight and illumination time, as well as the changes in molecular weight distribution and illumination time of the nano-titanium dioxide polyethylene composite material prepared in Application Example 1 of this disclosure.

[0121] like Figure 7 As shown, the number-average molecular weight of the nano-titanium dioxide-polyethylene composite material prepared in Example 1 decreased with increasing light irradiation time. The degradation rate was fastest within 0-30 hours, and gradually slowed down after 60 hours. This is mainly because as the reaction proceeds, the absorption capacity of titanium dioxide for ultraviolet light decreases, resulting in a gradual reduction in the number of electrons and holes generated; and as the reaction proceeds, polyethylene molecules gradually break down from larger molecular weights into smaller molecular weights, thus reducing the degradation rate of polyethylene. The nano-titanium dioxide-polyethylene composite material prepared by melt blending (Comparative Example 1) showed cross-linking under 365nm UV irradiation, and its molecular weight increased slightly.

[0122] Comparative Example 2: Preparation and Material Properties of Nano-Heterojunction Polyethylene Composites (denoted as "LDPE-Heterojunction") Using Melt Blending

[0123] 9.9g of LDPE (Maoming Petrochemical, 951-050), 0.1g of wood flour and 0.1g of BHT (antioxidant) were melt-blended and then extruded using a twin-screw extruder to obtain a nano-heterogeneous (1%) polyethylene composite material.

[0124] Figure 8The stress-strain curves of the nano-heterojunction polyethylene composite material prepared in Application Example 2 of this disclosure and the nano-heterojunction polyethylene composite material prepared by melt blending in Comparative Example 2 are illustrated schematically.

[0125] like Figure 8 The tensile strength of the nano-heterojunction polyethylene composite material prepared by melt blending in Comparative Example 2 is 10 ± 2 MPa, and the elongation at break is 460 ± 20%. The tensile strength of the nano-heterojunction polyethylene composite material prepared in Application Example 2 is 45 ± 2 MPa, and the elongation at break is 800 ± 20%. The comparison shows that the mechanical properties of the nano-heterojunction polyethylene composite material prepared in Application Example 2 are superior to those of the nano-heterojunction polyethylene composite material prepared by melt blending in Comparative Example 2.

[0126] Photodegradation tests were performed on polyethylene in Case 2 and polyethylene in Comparative Example 2. The specific test process is as follows:

[0127] The polymer was made into a thin film sample with dimensions of 20×10×0.5mm. The photodegradation experiment of the two nano-heterojunction polyethylene composite materials prepared by the two methods was carried out using a 365nm UV lamp. Samples were taken at regular intervals, and the degree of polymer degradation was detected by molecular weight.

[0128] Figure 9 The diagram illustrates a comparison of the photodegradation effects of the nano-heterojunction polyethylene composite material prepared in Application Example 2 of this disclosure and the nano-heterojunction polyethylene composite material prepared by melt blending in Comparative Example 2.

[0129] like Figure 9 As shown, after normalizing the molecular weight, it was found that the number-average molecular weight of the nano-heterojunction polyethylene composite material prepared in Application Example 2 decreased with the extension of light exposure time. With an addition of 1 wt%, it could be degraded to a molecular weight of 4000 in about 2 days (50 h). The photodegradation efficiency was significantly higher than that of the nano-heterojunction polyethylene composite material prepared by melt blending in Comparative Example 2.

[0130] Analysis shows that when using a twin-screw extruder to prepare composite materials, the vigorous chain segment movement in the twin-screw extruder causes interfacial separation of the heterojunction, affecting the photodegradation activity of the nano-semiconductor materials. In contrast, the method proposed in this disclosure can prepare heterojunction / polyethylene composite materials with two semiconductors in a gentler manner.

[0131] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A heterogeneous photodegradation catalyst, comprising: Nano-semiconductors, wherein the nano-semiconductors have photocatalytic degradation properties; Polyacrylic acid particles are formed using nano-semiconductors as condensation nuclei, and a catalytically active layer is formed on their surface. and α-Diimine nickel metal catalyst adsorbed on polyacrylic acid particles; The polyacrylic acid particles contain carboxyl-metal ion dynamic crosslinking points to achieve the loading of α-diimine nickel metal catalyst.

2. The heterogeneous photodegradation catalyst according to claim 1, wherein, The nano-semiconductor includes at least one of titanium dioxide, cuprous oxide, nano-iron stearate, and titanium dioxide / cuprous oxide heterojunction. The nano-semiconductor has a particle size of 5-100 nm.

3. A method for preparing the heterogeneous photodegradation catalyst as described in claim 1 or 2, comprising: At the first reaction temperature, after dissolving and uniformly mixing the nano-semiconductor and the alkylaluminum-protected olefin monomer, a co-catalyst and an α-diimine nickel metal catalyst are added. The polymerization reaction of the olefin monomers occurs at the second reaction temperature. After heterogeneous nucleation, a polyolefin catalytic active layer is formed on the surface of the nano-semiconductor. After standing or stirring for a period of time, the mixture is cooled to the third reaction temperature to obtain the heterogeneous photodegradation catalyst. The alkylaluminum-protected olefinic acid monomer is selected from bis(10-undecenoic acid)aluminum chloride, bis(5-hexenoic acid)aluminum chloride, bis(4-pentenoic acid)aluminum chloride, bis(trans-oleic acid)aluminum chloride, bis(acrylic acid)aluminum chloride, and bis(5-norbornene-2-carboxylic acid)aluminum chloride.

4. The method according to claim 3, wherein: The mass ratio of the alkylaluminum-protected olefin monomer to the nano-semiconductor is 1:0.1-50; The molar ratio of the α-diimine nickel metal catalyst to the alkylaluminum protected olefin monomer is 1:50-5000.

5. The method according to claim 3, wherein: The molar ratio of the co-catalyst to the α-diimine nickel metal catalyst is 1:100~5000; The cocatalyst includes one or more of diethylaluminum chloride, methylaluminoxane, ethylaluminum dichloride, triisobutylaluminum, and tris(pentafluorophenyl)boron.

6. The method according to claim 3, wherein: The first reaction temperature range is 0~50℃; The second reaction temperature range is -30~50℃; The third reaction temperature range is -80 to 15°C; The time for standing or stirring is 4-12 hours.

7. A method for preparing a photodegradable functionalized polyethylene composite material, comprising: Using the heterogeneous photodegradation catalyst of claim 1 or 2, ethylene monomers are homopolymerized in an organic solvent to obtain a photodegradable polyethylene composite material, wherein the polyacrylic acid catalytic active layer acts as a coupling agent to combine the polyethylene and the nano-semiconductor.

8. The method according to claim 7, wherein, In the homopolymerization reaction, the partial pressure of ethylene gas is 1-40 atmospheres, the homopolymerization reaction time is 2 min to 8 h, and the homopolymerization reaction temperature is -30 to 80℃.

9. The method according to claim 7, wherein, The organic solvent includes at least one of the following: Petroleum ether, pentane, hexane, heptane, octane, hydrogenated gasoline, methylcyclohexane, decahydronaphthalene, methylcyclohexane, cyclohexane, benzene, toluene, xylene, hydrogenated gasoline, dichloromethane, chloroform, chlorobenzene, and dichlorobenzene.

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