Polypropylene / polyester composite material recovery process

Abstract

The invention discloses a polypropylene / polyester composite material recovery process, belongs to the technical field of composite material recovery, and solves the problems of easy separation, good cycle performance and wide application range of composite polyester in the prior art. The preparation method comprises the following steps: putting polyethylene glycol terephthalate, a catalyst and dihydric alcohol into an alcoholysis kettle through a screw extruder for alcoholysis, evaporating dihydric alcohol alcoholysis liquid, purifying BHET, and grafting blended polypropylene. According to the invention, the dissolving characteristics of polypropylene and polyester are utilized, and polypropylene and polyester are respectively dissolved in different solvents in the composite solvent, so that the rapid treatment of waste polyester is realized, the purity of polypropylene is improved, and the treatment direction of waste polyester is expanded; the separated polyethylene glycol terephthalate is depolymerized, and the alcoholysis solution is evaporated during polymerization regeneration, so that low molecules in the dihydric alcohol alcoholysis solution are removed and then are used as alcoholysis raw materials for circular reaction again, and the cyclic utilization of steam is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material recycling, and in particular relates to a polypropylene / polyester composite material recycling process. Background Art

[0002] Regenerated polyester fibers are spun from polyester melts synthesized from textile waste (polyester-based clothing, scraps, etc.) and low-value, low-quality, used polyester bottles through alcoholysis and repolymerization. This represents a new method for high-value recycling of waste polyester materials. Polypropylene, a thermoplastic polymer derived from propylene monomer, boasts abundant and affordable raw materials. It also possesses high mechanical properties, including high tensile strength and rigidity, as well as excellent chemical resistance and stability in a wide range of chemical environments. These advantages have led to its widespread use in various fields. However, due to polypropylene's low melt strength and lack of strain hardening, it is difficult to maintain cell stability during the foaming process, resulting in cell breakage and merging, which affects foam quality. During extrusion molding, melt fracture is a common occurrence, affecting the surface quality and dimensional accuracy of the finished product. To mitigate these shortcomings, modifications to the original polypropylene and polyethylene materials are necessary. Existing methods use radiation or chemical methods to cross-link polypropylene to improve melt strength, but the degree of cross-linking is difficult to control, which can easily lead to excessive or insufficient cross-linking, affecting material properties. Among them, simple blending modification can improve certain properties of polypropylene to a certain extent, but the interfacial bonding strength is insufficient, limiting the overall performance improvement. The melt method in grafting modification is prone to side reactions, which makes the solution method have the disadvantages of solvent recovery and high cost. Summary of the Invention

[0003] The purpose of the present invention is to address the deficiencies in the prior art and provide a polypropylene / polyester composite material recycling process with easy separation of composite polyester, good recycling performance and wide application range.

[0004] In order to achieve the above technical objectives, the technical solution adopted by the polypropylene / polyester composite material recycling process of the present invention is: A polypropylene / polyester composite material recycling process comprises the following steps: S1: Add an appropriate amount of composite solvent to waste polyester material according to the weight ratio, dissolve at 80-120°C for 1-2 hours, filter and dry to obtain polypropylene and polyethylene terephthalate; S2: Put polyethylene terephthalate, catalyst and diol into the alcoholysis reactor through a screw extruder, heat it to a suitable temperature, stir and alcoholize for a period of time, and then cool the reaction solution to 80-160℃ and filter it while hot; S3: The diol alcoholysis liquid enters the evaporation chamber, and the diol alcoholysis liquid is evaporated by thin film, low molecular weight is evaporated off, and BHET is purified by sublimation. The low molecular weight vapor generated by the alcoholysis liquid is recycled as the alcoholysis raw material; S4: adding 100 parts of polypropylene, 2 to 5 parts of grafting monomer and 0.6 to 1.25 parts of initiator by weight into a high-speed mixer, and mixing at 600 to 800 r / min for 8 to 10 minutes to prepare a mixture; S5: adding the mixture to a twin-screw extruder, and performing a grafting reaction at a temperature of 160-180° C. and a screw speed of 280-300 r / min to obtain a grafted product; S6: In parts by weight, the grafted material, 8 to 12 parts of the copolymer mixture, and 5.4 to 10.9 parts of the anti-additive are added to a high-speed mixer, and mixed at 600 to 800 r / min for 8 to 10 minutes. After the mixing is completed, the materials are added to a twin-screw extruder, melt-extruded at 150 to 160°C and a screw speed of 180 to 230 r / min, and the extrudate is then fed into a pelletizer to obtain particles of uniform size.

[0005] In step S1, the composite solvent includes one or more of ethylene glycol, dimethylacetamide, and xylene.

[0006] In step S2, the catalyst includes zinc acetate or hydrated zinc acetate, the reaction temperature of the alcoholysis kettle is raised to 190-220° C., the temperature is maintained and the pressure is controlled to 0.01-1.0 MPa, and the reaction is stirred for 2-3 hours.

[0007] In step S4, the grafting monomer includes maleic anhydride, and the initiator includes dicumyl peroxide, di-tert-butyl peroxide and tert-butyl peroxide.

[0008] In the step S6, the copolymer mixture is ethylene-vinyl acetate copolymer.

[0009] In step S6, the auxiliary agents include an antioxidant, a lubricant and a toughening agent, the antioxidant is 1010, the lubricant is calcium stearate, and the toughening agent is a polyolefin elastomer.

[0010] Compared with the prior art, the present invention has the following beneficial effects: The present invention utilizes the solubility characteristics of polypropylene and polyester, dissolves them in different solvents in a composite solvent, realizes rapid processing of waste polyester, improves the purity of polypropylene, and expands the processing direction of waste polyester; depolymerizes the separated polyethylene terephthalate, evaporates the alcoholysis liquid during polymerization regeneration, removes low molecular weight diols from the alcoholysis liquid and recycles the diols as alcoholysis raw materials for reaction, solves the problem of difficult diol processing in conventional polyester alcoholysis reaction, and realizes the recycling of steam; grafts and blends the polypropylene after the waste polyester separation process, effectively improves the polarity of the polypropylene, enables the polypropylene to better adhere to polar materials, and is blended with inorganic materials and polar polymers, broadens the application range of the waste polyester, increases the melt strength of the polypropylene, and improves processing properties such as foaming, extrusion molding and blow molding. DETAILED DESCRIPTION

[0011] The invention is further described below in conjunction with specific embodiments: Example 1 A polypropylene / polyester composite material recycling process comprises the following steps: S1: Add appropriate amounts of ethylene glycol, dimethylacetamide and xylene composite solvent to waste polyester materials in proportion by weight, dissolve at 80-120°C for 1-2 hours, filter and dry the materials to obtain polypropylene and polyethylene terephthalate; S2: Polyethylene terephthalate, zinc acetate or hydrated zinc acetate and diol are put into an alcoholysis reactor through a screw extruder. The reaction temperature of the alcoholysis reactor is raised to 190-220°C, kept warm and the pressure is controlled at 0.01-1.0 MPa. The reaction is stirred for 2-3 hours. The reaction solution is cooled to 80-160°C and filtered while hot. S3: The diol alcoholysis liquid enters the evaporation chamber, and the diol alcoholysis liquid is evaporated by thin film, low molecular weight is evaporated off, and BHET is purified by sublimation. The low molecular weight vapor generated by the alcoholysis liquid is recycled as the alcoholysis raw material; S4: adding 100 parts by weight of polypropylene, 2 parts of maleic anhydride, and 0.6 parts of dicumyl peroxide, a mixed initiator of di-tert-butyl peroxide and tert-butyl peroxide into a high-speed mixer, and mixing at 600-800 r / min for 8-10 minutes to prepare a mixture; S5: adding the mixture to a twin-screw extruder, and performing a grafting reaction at a temperature of 160-180° C. and a screw speed of 280-300 r / min to obtain a grafted product; S6: In parts by weight, 10 parts of grafted material, 8 parts of ethylene-vinyl acetate copolymer, and 5.4 parts of anti-additive are added into a high-speed mixer, and mixed at 600-800r / min for 8-10 minutes. After mixing, the materials are added into a twin-screw extruder, and melt-extruded at 150-160°C and a screw speed of 180-230r / min. The extrudate is then put into a pelletizer to obtain particles of uniform size. The additives include antioxidants, lubricants, and toughening agents. The antioxidant is 1010, the lubricant is calcium stearate, and the toughening agent is polyolefin elastomer.

[0012] Example 2 A polypropylene / polyester composite material recycling process comprises the following steps: S1: Add appropriate amounts of ethylene glycol, dimethylacetamide and xylene composite solvent to waste polyester materials in proportion by weight, dissolve at 80-120°C for 1-2 hours, filter and dry the materials to obtain polypropylene and polyethylene terephthalate; S2: Polyethylene terephthalate, zinc acetate or hydrated zinc acetate and diol are put into an alcoholysis reactor through a screw extruder. The reaction temperature of the alcoholysis reactor is raised to 190-220°C, kept warm and the pressure is controlled at 0.01-1.0 MPa. The reaction is stirred for 2-3 hours. The reaction solution is cooled to 80-160°C and filtered while hot. S3: The diol alcoholysis liquid enters the evaporation chamber, and the diol alcoholysis liquid is evaporated by thin film, low molecular weight is evaporated off, and BHET is purified by sublimation. The low molecular weight vapor generated by the alcoholysis liquid is recycled as the alcoholysis raw material; S4: adding 100 parts by weight of polypropylene, 5 parts of maleic anhydride, and 1.25 parts of dicumyl peroxide, a mixed initiator of di-tert-butyl peroxide and tert-butyl peroxide into a high-speed mixer, and mixing at 600-800 r / min for 8-10 minutes to prepare a mixture; S5: adding the mixture to a twin-screw extruder, and performing a grafting reaction at a temperature of 160-180° C. and a screw speed of 280-300 r / min to obtain a grafted product; S6: In parts by weight, 10 parts of grafted material, 12 parts of ethylene-vinyl acetate copolymer, and 10.9 parts of anti-additive are added to a high-speed mixer, and mixed at 600-800r / min for 8-10 minutes. After mixing, the materials are added to a twin-screw extruder, melt-extruded at 150-160°C and a screw speed of 180-230r / min, and the extrudate is fed into a pelletizer to obtain particles of uniform size. The additives include antioxidants, lubricants, and toughening agents. The antioxidant is 1010, the lubricant is calcium stearate, and the toughening agent is polyolefin elastomer.

[0013] Example 3 A polypropylene / polyester composite material recycling process comprises the following steps: S1: Add appropriate amounts of ethylene glycol, dimethylacetamide and xylene composite solvent to waste polyester materials in proportion by weight, dissolve at 80-120°C for 1-2 hours, filter and dry the materials to obtain polypropylene and polyethylene terephthalate; S2: Polyethylene terephthalate, zinc acetate or hydrated zinc acetate and diol are put into an alcoholysis reactor through a screw extruder. The reaction temperature of the alcoholysis reactor is raised to 190-220°C, kept warm and the pressure is controlled at 0.01-1.0 MPa. The reaction is stirred for 2-3 hours. The reaction solution is cooled to 80-160°C and filtered while hot. S3: The diol alcoholysis liquid enters the evaporation chamber, and the diol alcoholysis liquid is evaporated by thin film, low molecular weight is evaporated off, and BHET is purified by sublimation. The low molecular weight vapor generated by the alcoholysis liquid is recycled as the alcoholysis raw material; S4: adding 100 parts by weight of polypropylene, 3.5 parts of maleic anhydride, 0.92 parts of dicumyl peroxide, and a mixed initiator of di-tert-butyl peroxide and tert-butyl peroxide into a high-speed mixer, and mixing at 600-800 r / min for 8-10 minutes to prepare a mixture; S5: adding the mixture to a twin-screw extruder, and performing a grafting reaction at a temperature of 160-180° C. and a screw speed of 280-300 r / min to obtain a grafted product; S6: In parts by weight, 10 parts of grafted material, 10 parts of ethylene-vinyl acetate copolymer, and 8.15 parts of anti-additive are added to a high-speed mixer, and mixed at 600-800r / min for 8-10 minutes. After mixing, the materials are added to a twin-screw extruder, melt-extruded at 150-160°C and a screw speed of 180-230r / min, and the extrudate is fed into a pelletizer to obtain particles of uniform size. The additives include an antioxidant, a lubricant, and a toughening agent. The antioxidant is 1010, the lubricant is calcium stearate, and the toughening agent is a polyolefin elastomer.

[0014] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. All equivalent changes and modifications in the shape, structure, characteristics and spirit of the claims of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A polypropylene / polyester composite material recycling process, characterized in that: The following steps are involved: S1: Add an appropriate amount of composite solvent to waste polyester material according to the weight ratio, dissolve at 80-120°C for 1-2 hours, filter and dry to obtain polypropylene and polyethylene terephthalate; S2: Put polyethylene terephthalate, catalyst and diol into the alcoholysis reactor through a screw extruder, heat it to a suitable temperature, stir and alcoholize for a period of time, and then cool the reaction solution to 80-160℃ and filter it while hot; S3: The diol alcoholysis liquid enters the evaporation chamber, and the diol alcoholysis liquid is evaporated by thin film, low molecular weight is evaporated off, and BHET is purified by sublimation. The low molecular weight vapor generated by the alcoholysis liquid is recycled as the alcoholysis raw material; S4: adding 100 parts of polypropylene, 2 to 5 parts of grafting monomer and 0.6 to 1.25 parts of initiator by weight into a high-speed mixer, and mixing at 600 to 800 r / min for 8 to 10 minutes to prepare a mixture; S5: adding the mixture to a twin-screw extruder, and performing a grafting reaction at a temperature of 160-180° C. and a screw speed of 280-300 r / min to obtain a grafted product; S6: In parts by weight, the grafted material, 8 to 12 parts of the copolymer mixture, and 5.4 to 10.9 parts of the anti-additive are added to a high-speed mixer, and mixed at 600 to 800 r / min for 8 to 10 minutes. After the mixing is completed, the materials are added to a twin-screw extruder, melt-extruded at 150 to 160°C and a screw speed of 180 to 230 r / min, and the extrudate is then fed into a pelletizer to obtain particles of uniform size.

2. The polypropylene / polyester composite material recycling process according to claim 1, characterized in that: In step S1, the composite solvent includes one or more of ethylene glycol, dimethylacetamide, and xylene.

3. The polypropylene / polyester composite material recycling process according to claim 1, characterized in that: In step S2, the catalyst includes zinc acetate or hydrated zinc acetate, the reaction temperature of the alcoholysis kettle is raised to 190-220° C., the temperature is maintained and the pressure is controlled to 0.01-1.0 MPa, and the reaction is stirred for 2-3 hours.

4. The polypropylene / polyester composite material recycling process according to claim 1, characterized in that: In step S4, the grafting monomer includes maleic anhydride, and the initiator includes dicumyl peroxide, di-tert-butyl peroxide and tert-butyl peroxide.

5. The polypropylene / polyester composite material recycling process according to claim 1, characterized in that: In the step S6, the copolymer mixture is ethylene-vinyl acetate copolymer.

6. The polypropylene / polyester composite material recycling process according to claim 1, characterized in that: In step S6, the auxiliary agents include an antioxidant, a lubricant and a toughening agent, the antioxidant is 1010, the lubricant is calcium stearate, and the toughening agent is a polyolefin elastomer.