Functionalized polyurethane cross-linking agent based on waste PET depolymerization monomer and preparation method of functionalized polyurethane cross-linking agent

Abstract

The invention discloses a functionalized polyurethane cross-linking agent based on a waste PET (Polyethylene Terephthalate) depolymerization monomer as well as a preparation method and application of the functionalized polyurethane cross-linking agent. The preparation method comprises the following steps: carrying out organic-inorganic hybridization on the waste PET depolymerization monomer bis (2-ethoxyl) terephthalate and a functionalized filler with active hydroxyl by utilizing a coupling agent, namely isocyanate propyl triethoxyl silane; according to the present invention, the functional polyurethane cross-linking agent is prepared, and the obtained functional polyurethane cross-linking agent has characteristics of versatility, excellent mechanical property, electric conduction, heat conduction, electromagnetic shielding effect and other properties, and further has characteristics of complete structure, small particle size distribution and excellent dispersion stability; the method can be further used for preparing a functional polyurethane composite material with the properties of electric conduction, heat conduction, electromagnetic shielding effect and the like.

Description

Technical Field:

[0001] The present invention relates to the technical field of polyurethane crosslinking agents, and particularly relates to a functionalized polyurethane crosslinking agent based on depolymerized monomers of waste PET and a preparation method thereof. Background Art:

[0002] Polyethylene terephthalate (PET) is a polyester material widely used in the packaging field. With the development of society and economy, there are more and more waste PETs, which not only cause environmental pollution but also result in serious waste of resources. How to recycle and reuse waste PET with high value is the current focus of people's attention.

[0003] Polyurethane is a general polymer and can be applied in multiple fields. Chinese Patent Application with Publication No. CN117700730A discloses a boron-containing crosslinking agent for thermoplastic polyurethane elastomers, a preparation method thereof and an application. This preparation method reacts polyethyleneimine with aldehyde group-containing phenylboronic acid compounds to prepare a boron-containing crosslinking agent. The efficiency of preparing the crosslinking agent by this method is relatively low, and although this crosslinking agent can be applied in thermoplastic polyurethane elastomers, it can only improve the mechanical properties of polyurethane, but cannot endow polyurethane with functions such as conductivity, heat conduction, and electromagnetic shielding, which limits its application scope.

[0004] In recent years, functional fillers with active hydroxyl groups on the surface such as MXene, graphene, hydroxylated carbon nanotubes, and hydroxylated boron nitride have been used for organic modification to prepare various functional polymer composites due to their large specific surface area, high electrical conductivity and thermal conductivity, excellent electromagnetic shielding effect, etc. If functional fillers with active hydroxyl groups on the surface and depolymerized monomers of waste PET can be organically-inorganically hybridized through a coupling agent isocyanatopropyltriethoxysilane to prepare a functionalized polyurethane crosslinking agent, it has an incomparable effect on enhancing the functionality of polyurethane. Summary of the Invention:

[0005] The purpose of the present invention is to provide a functionalized polyurethane crosslinking agent based on depolymerized monomers of waste PET, a preparation method thereof and an application, which solves the problem that the existing polyurethane crosslinking agent cannot endow polyurethane with functions such as conductivity, heat conduction, and electromagnetic shielding, and also solves the problem that waste PET in the prior art has no high-value utilization.

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

[0007] A functionalized polyurethane crosslinking agent based on depolymerized monomers of waste PET, and this crosslinking agent is prepared from the following raw materials in parts by weight:

[0008]

[0009] The functional filler is one or more of MXene, graphene oxide (GO), hydroxylated carbon nanotubes (CNT), and hydroxylated boron nitride (BN); the catalyst is one or more of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate.

[0010] The organic solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide, acetone, and methyl ethyl ketone.

[0011] The specific preparation method of the waste PET depolymerization monomer bis(2-hydroxyethyl) terephthalate includes the following steps: Under a protective atmosphere, waste PET and ethylene glycol are in a mass ratio of 1:(2 - 4), and react at 180 - 200 °C for 3 - 5 h under the action of the catalyst zinc acetate, and bis(2-hydroxyethyl) terephthalate (BHET) is obtained through filtration, rotary evaporation, cooling crystallization, centrifugal washing, and drying.

[0012] The preparation method of the functionalized polyurethane crosslinking agent includes the following steps:

[0013] 1) Under a protective atmosphere, dissolve the waste PET depolymerization monomer bis(2-hydroxyethyl) terephthalate in a mixture of an organic solvent and the coupling agent isocyanatopropyltriethoxysilane, and react at 60 - 80 °C for 1 - 3 h under the action of a catalyst to obtain isocyanatopropyltriethoxysilane-modified bis(2-hydroxyethyl) terephthalate;

[0014] 2) Add the dispersion of the functional filler with active hydroxyl groups to step 1), and react at 50 - 70 °C for 2 - 4 h under the action of a catalyst to obtain a crude product of the functionalized polyurethane crosslinking agent with the functional filler loaded on bis(2-hydroxyethyl) terephthalate;

[0015] 3) Centrifuge and wash the crude product of the functionalized polyurethane crosslinking agent, and vacuum dry it to obtain a purified functionalized polyurethane crosslinking agent.

[0016] Preferably, in step 1), the weight ratio of the organic solvent to bis(2-hydroxyethyl) terephthalate (BHET) is (5 - 15):(0.5 - 1.5), the molar ratio of bis(2-hydroxyethyl) terephthalate to the coupling agent isocyanatopropyltriethoxysilane is 1:1, the catalyst is one or more of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate; the dosage of the catalyst is 1 - 5% of the mass of the depolymerization monomer bis(2-hydroxyethyl) terephthalate.

[0017] Preferably, the functional filler with active hydroxyl groups in step 2) is one or more of MXene, graphene oxide (GO), hydroxylated carbon nanotubes, and hydroxylated boron nitride.

[0018] Preferably, the weight ratio of the organic solvent to the functional filler in step 2) is (5 - 15):(0.1 - 0.3), and the solvent used for the dispersion liquid in step 2) is one or more of N-methylpyrrolidone, N,N-dimethylformamide, acetone, and methyl ethyl ketone; the catalyst in step 2) is one or more of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate; the dosage of the catalyst is 1 - 5% of the mass of the functional filler.

[0019] The functional filler of the present invention has properties such as electrical conductivity, thermal conductivity, and electromagnetic shielding effect. The present invention utilizes the polyhydroxy structure of the functional filler to react with the depolymerization monomer of waste PET, bis(2-hydroxyethyl) terephthalate (BHET), through the coupling agent isocyanatopropyltriethoxysilane to form a functionalized crosslinking agent with BHET grafted on the surface of the functional filler. BHET has a rigid benzene ring structure and excellent mechanical properties; therefore, the functionalized polyurethane crosslinking agent prepared by the present invention has versatility, not only has excellent mechanical properties, but also has properties such as electrical conductivity, thermal conductivity, and electromagnetic shielding effect.

[0020] Moreover, the functionalized polyurethane crosslinking agent obtained by the present invention has a complete structure, a small particle size distribution, and excellent dispersion stability, can be used as a raw material for preparing functionalized polyurethane, and can further be used to prepare functionalized polyurethane composites with properties such as electrical conductivity, thermal conductivity, and electromagnetic shielding effect.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1) The functional filler of the present invention has properties such as electrical conductivity, thermal conductivity, and electromagnetic shielding effect. The present invention uses the coupling agent isocyanatopropyltriethoxysilane to carry out organic-inorganic hybridization of the depolymerization monomer of waste PET, bis(2-hydroxyethyl) terephthalate (BHET), and the functionalized filler with active hydroxyl groups to prepare a functionalized polyurethane crosslinking agent. The obtained functionalized polyurethane crosslinking agent has versatility, not only has excellent mechanical properties, but also has properties such as electrical conductivity, thermal conductivity, and electromagnetic shielding effect. Moreover, the obtained functionalized polyurethane crosslinking agent has a complete structure, a small particle size distribution, and excellent dispersion stability, and can further be used to prepare functionalized polyurethane composites with properties such as electrical conductivity, thermal conductivity, and electromagnetic shielding effect.

[0023] 2) The present invention realizes the high-value reuse of waste PET. The raw materials are cheap and rich in resources. At the same time, the dispersion of the functional filler with active hydroxyl groups in the organic solvent is improved, and the obtained functionalized polyurethane crosslinking agent can endow polyurethane with excellent functionality when applied to the field of preparing functionalized polyurethane materials. Description of the Drawings:

[0024] Figure 1 It is a flowchart for the preparation of the functionalized polyurethane crosslinking agent in Example 1.

[0025] Figure 2 Scanning electron microscope photos of MXene and the functionalized polyurethane crosslinker prepared in Example 2; among them, a is MXene; b is the functionalized polyurethane crosslinker prepared in Example 2;

[0026] Figure 3 Particle size distribution diagrams of MXene and the functionalized polyurethane crosslinker prepared in Example 2; among them, a is MXene; b is the functionalized polyurethane crosslinker prepared in Example 2;

[0027] Figure 4 Dispersion photos of MXene and the functionalized polyurethane crosslinker prepared in Example 2 in the organic solvent N,N-dimethylformamide; among them, the left figure is MXene; the right figure is the functionalized polyurethane crosslinker prepared in Example 2. Detailed implementation method:

[0028] The following is a further description of the present invention, rather than a limitation of the present invention.

[0029] Example 1:

[0030] (1) Waste PET and ethylene glycol were mixed in a mass ratio of 1:4 and 3 wt% of the catalyst zinc acetate (3% of the PET mass) and added to a reaction vessel, stirred and reacted at 190 °C for 3 h, and the product was filtered, rotary evaporated, cooled and crystallized, centrifugally washed, and dried to obtain the depolymerized monomer bis(2-hydroxyethyl) terephthalate (BHET).

[0031] (2) According to the molar ratio of bis(2-hydroxyethyl) terephthalate to the coupling agent isopropyltriethoxysilane of 1:1, 1 part by weight (1 gram) of bis(2-hydroxyethyl) terephthalate (BHET) was dissolved in 10 parts by weight of N,N-dimethylformamide, added to a reactor, and then 0.97 part by weight of the coupling agent isopropyltriethoxysilane (IPTS) and 0.03 part by weight of the catalyst dibutyltin dilaurate were added, and stirred at 70 °C at a speed of 150 rpm for 2 h to obtain isopropyltriethoxysilane-modified bis(2-hydroxyethyl) terephthalate.

[0032] (3) 10 mL of a 10 mg / mL (0.1 part by weight) MXene N,N-dimethylformamide dispersion was added to step (2), and then 0.003 part by weight of the catalyst dibutyltin dilaurate was added, and reacted at 60 °C for 3 h to obtain a crude product of the functionalized polyurethane crosslinker MXene-s-BHET loaded with functional fillers bis(2-hydroxyethyl) terephthalate;

[0033] (4) Centrifuge and wash the crude product of the functionalized polyurethane crosslinking agent in step (3), and vacuum dry it to obtain the purified functionalized polyurethane crosslinking agent MXene-s-BHET.

[0034] The preparation principle diagram of the functionalized polyurethane crosslinking agent prepared in this example is as Figure 1 shown. It can be seen from Figure 1 that the hydroxyl group of BHET and the isocyanate group on IPTS can react under anhydrous and nitrogen atmosphere to obtain the intermediate coupling agent-modified BHET (s-BHET). Then, under the action of a catalyst, the silicon-oxygen bond on s-BHET breaks and reacts with the hydroxyl group on MXene to generate the functionalized polyurethane crosslinking agent MXene-s-BHET.

[0035] Example 2

[0036] (1) The same as step (1) of Example 1.

[0037] (2) The same as step (2) of Example 1.

[0038] (3) Add 20 mL of a 10 mg / mL (0.2 parts by weight) MXene N,N-dimethylformamide dispersion to step (2), and then add 0.006 parts by weight of the catalyst dibutyltin dilaurate. React at 60 °C for 3 h to obtain the crude product of the functionalized polyurethane crosslinking agent MXene-s-BHET loaded with functional fillers of bis(2-hydroxyethyl) terephthalate;

[0039] (4) Centrifuge and wash the crude product of the functionalized polyurethane crosslinking agent in step (3), and vacuum dry it to obtain the purified functionalized polyurethane crosslinking agent MXene-s-BHET.

[0040] The scanning electron microscope photos of the functionalized polyurethane crosslinking agent prepared in this example are as Figure 2 shown. As can be seen from a in Figure 2 , the surface of unmodified MXene is relatively smooth and tidy, and there is a loose stacking structure between the lamellae (the interlayer spacing is small). However, the surface of the modified MXene is relatively rough, and the interlayer spacing increases ( Figure 2 b), which is attributed to the attachment of organic small molecule BHET particles on the surface of MXene. The particle size distribution of the functionalized polyurethane crosslinking agent prepared in this example is as Figure 3 shown. Figure 3 a and b in Figure 3 compare the particle size distributions of MXene and MXene-s-BHET. As shown in a in Figure 3In b). The dispersion photo of the functionalized polyurethane crosslinking agent prepared in this example in the organic solvent N,N-dimethylformamide is as Figure 4 shown. It can be seen from Figure 4 that, compared with MXene, MXene-s-BHET has long-term stable dispersion in the DMF solvent.

[0041] Example 3

[0042] (1) The same as step (1) of Example 1.

[0043] (2) The same as step (2) of Example 1.

[0044] (3) Add 30 mL of a 10 mg / mL (0.3 parts by weight) N,N-dimethylformamide dispersion of MXene to step (2), and then add 0.009 parts by weight of the catalyst dibutyltin dilaurate, and react at 60 °C for 3 h to obtain a crude product of the functionalized polyurethane crosslinking agent MXene-s-BHET loaded with functional fillers bis(2-hydroxyethyl) terephthalate;

[0045] (4) Centrifuge and wash the crude product of the functionalized polyurethane crosslinking agent in step (3), and vacuum dry to obtain the purified functionalized polyurethane crosslinking agent MXene-s-BHET.

[0046] Example 4

[0047] (1) The same as step (1) of Example 1.

[0048] (2) The same as step (2) of Example 1.

[0049] (3) Add 20 mL of a 10 mg / mL (0.2 parts by weight) N,N-dimethylformamide dispersion of graphene oxide (GO) to step (2), and then add 0.006 parts by weight of the catalyst dibutyltin dilaurate, and react at 60 °C for 3 h to obtain a crude product of the functionalized polyurethane crosslinking agent GO-s-BHET loaded with functional fillers bis(2-hydroxyethyl) terephthalate;

[0050] (4) Centrifuge and wash the crude product of the functionalized polyurethane crosslinking agent in step (3), and vacuum dry to obtain the purified functionalized polyurethane crosslinking agent GO-s-BHET.

[0051] Example 5

[0052] (1) The same as step (1) of Example 1.

[0053] (2) The same as step (2) of Example 1.

[0054] (3) Add 20 mL of a 10 mg / mL (0.2 parts by weight) N,N-dimethylformamide dispersion of hydroxylated carbon nanotubes to step (2), and then add 0.006 parts by weight of the catalyst dibutyltin dilaurate. React at 60 °C for 3 h to obtain a crude product of the functionalized polyurethane crosslinker CNT-s-BHET loaded with terephthalic acid bis(2-hydroxyethyl) ester as the functional filler;

[0055] (4) Centrifuge and wash the crude product of the functionalized polyurethane crosslinker in step (3), and then dry it under vacuum to obtain the purified functionalized polyurethane crosslinker CNT-s-BHET.

[0056] Example 6

[0057] (1) The same as step (1) of Example 1.

[0058] (2) The same as step (2) of Example 1.

[0059] (3) Add 20 mL of a 10 mg / mL (0.2 parts by weight) N,N-dimethylformamide dispersion of hydroxylated boron nitride to step (2), and then add 0.006 parts by weight of the catalyst dibutyltin dilaurate. React at 60 °C for 3 h to obtain a crude product of the functionalized polyurethane crosslinker BN-s-BHET loaded with terephthalic acid bis(2-hydroxyethyl) ester as the functional filler;

[0060] (4) Centrifuge and wash the crude product of the functionalized polyurethane crosslinker in step (3), and then dry it under vacuum to obtain the purified functionalized polyurethane crosslinker BN-s-BHET.

[0061] Example 7: Application

[0062] In a reactor, add 6 parts by weight of poly(butylene adipate), 4 parts by weight of hexamethylene diisocyanate, and 1 part by weight of the chain extender terephthalic acid bis(2-hydroxyethyl) ester. First, stir at 70 °C at a speed of 100 rpm for 30 min, then add 0.12 parts by weight of the catalyst dibutyltin dilaurate (2 wt% of the weight of poly(butylene adipate)), and stir and react for 2 h to prepare a polyurethane prepolymer for standby.

[0063] Add 0.2 parts by weight of the polyurethane crosslinker MXene-s-BHET prepared in Example 1 to the polyurethane prepolymer in step (3), stir at 60 °C at a speed of 150 rpm for 2 h, and add 4 parts by weight of methyl ethyl ketone for dilution during the reaction to prepare a functionalized polyurethane emulsion. Then spread it evenly on a dry and clean mold to form a liquid layer with uniform thickness and a smooth and flat surface, dry it in an oven at 70 °C for 10 h, and remove the film to obtain the functionalized polyurethane film.

Claims

1. A functionalized polyurethane crosslinking agent based on depolymerized monomers of waste PET, characterized in that, The crosslinking agent is prepared from the following raw materials in parts by weight: The functional filler is one or more of MXene, graphene oxide, hydroxylated carbon nanotubes, and hydroxylated boron nitride; the catalyst is one or more of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate.

2. The functionalized polyurethane crosslinking agent according to claim 1, wherein The organic solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide, acetone, and methyl ethyl ketone.

3. The functionalized polyurethane crosslinking agent according to claim 1, characterized in that, The specific preparation method of the waste PET depolymerization monomer bis(2-hydroxyethyl) terephthalate includes the following steps: Under a protective atmosphere, waste PET and ethylene glycol are in a mass ratio of 1:(2-4), and react at 180-200 °C for 3-5 h under the action of the catalyst zinc acetate, and bis(2-hydroxyethyl) terephthalate is obtained through filtration, rotary evaporation, cooling crystallization, centrifugal washing, and drying.

4. The preparation method of the functionalized polyurethane crosslinking agent according to claim 1, characterized in that, It includes the following steps: 1) Under a protective atmosphere, dissolve the waste PET depolymerization monomer bis(2-hydroxyethyl) terephthalate in a mixture of an organic solvent and the coupling agent isocyanatopropyltriethoxysilane, and react at 60-80 °C for 1-3 h under the action of a catalyst to obtain isocyanatopropyltriethoxysilane-modified bis(2-hydroxyethyl) terephthalate; 2) Add the dispersion liquid of the functional filler with active hydroxyl groups to step 1), and react at 50-70 °C for 2-4 h under the action of a catalyst to obtain a crude product of a functionalized polyurethane crosslinking agent with the functional filler loaded with bis(2-hydroxyethyl) terephthalate; 3) The crude product of the functionalized polyurethane crosslinking agent is centrifugally washed and vacuum dried to obtain a purified functionalized polyurethane crosslinking agent.

5. The preparation method of the functionalized polyurethane crosslinking agent according to claim 4, wherein In step 1), the weight ratio of the organic solvent to bis(2-hydroxyethyl) terephthalate (BHET) is (5-15):(0.5-1.5), the molar ratio of bis(2-hydroxyethyl) terephthalate to the coupling agent isocyanatopropyltriethoxysilane is 1:1, the catalyst is one or more of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate; the dosage of the catalyst is 1-5% of the mass of the depolymerization monomer bis(2-hydroxyethyl) terephthalate.

6. The preparation method of the functionalized polyurethane crosslinking agent according to claim 4, wherein, In step 2), the functional filler with active hydroxyl groups is one or more of MXene, graphene oxide, hydroxylated carbon nanotubes, and hydroxylated boron nitride.

7. The preparation method of the functionalized polyurethane crosslinking agent according to claim 4, characterized in that, In step 2), the weight ratio of the organic solvent to the functional filler is (5-15):(0.1-0.3).

8. The preparation method of the functionalized polyurethane crosslinking agent according to claim 4, characterized in that, In step 2), the solvent used for the dispersion liquid is one or more of N-methylpyrrolidone, N,N-dimethylformamide, acetone, and methyl ethyl ketone.

9. The preparation method of the functionalized polyurethane crosslinking agent according to claim 4, characterized in that, In step 2), the catalyst is one or more of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate; the dosage of the catalyst is 1-5% of the mass of the functional filler.

10. Use of the functionalized polyurethane crosslinking agent according to claim 1, characterized in that, It is used to prepare a functionalized polyurethane composite material with conductive and heat-conductive, electromagnetic shielding effect properties.

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