Recycling method for thermosetting flame-retardant polyester composite material

Abstract

The invention belongs to the field of recycling of polyester materials, and particularly discloses a recycling method for a thermosetting flame-retardant polyester composite material, which comprises the following steps: S1, preparing a thermosetting phosphorus-containing flame-retardant polyester composite material; s2, degrading the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a degraded product of the thermosetting phosphorus-containing flame-retardant polyester composite material; s3, a product obtained after degradation of the thermosetting phosphorus-containing flame-retardant polyester composite material is separated and recycled, and a recycled product is obtained; and step S4, recycling the recovered product. According to the recycling and reusing method for the thermosetting flame-retardant polyester composite material, the thermosetting phosphorus-containing flame-retardant polyester composite material can be degraded, and the recycled product of the thermosetting phosphorus-containing flame-retardant polyester composite material can be reutilized.

Description

Technical Field

[0001] The present invention belongs to the field of recycling of polyester materials, and particularly relates to a method for recycling thermosetting flame-retardant polyester composites. Background Art

[0002] As one of the synthetic polymer materials with the largest global production, the applications of polyester materials have penetrated into many fields such as textiles, packaging, construction, and electronics. Thermoplastic polyesters represented by polyethylene terephthalate have an annual output of more than 80 million tons; while thermosetting polyesters (such as unsaturated polyester resins) have an annual consumption of more than 12 million tons in fields such as composites and automotive parts due to their excellent mechanical properties and corrosion resistance. Therefore, the development of efficient recycling technologies has become a key research focus in the global chemical industry. During the degradation process, the recycling of thermoplastic polyester materials such as polyethylene terephthalate is relatively easy, but for thermosetting materials such as unsaturated polyesters, the dense cross-linked network structure (cross-linking degree > 85%) formed after curing is difficult to be destroyed by conventional solvents or thermodynamic means, and the recycling and reuse are difficult. How to dispose of waste unsaturated polyesters that have reached the end of their service life has become an urgent problem to be solved.

[0003] At the same time, in the current research on the degradation and recycling of thermosetting polyester materials, the research objects often target pure polyester materials, ignoring the influence of additives, intrinsic functional structures, etc. in thermosetting polyester materials in actual applications. The actual waste often contains 30%-50% of additives such as glass fibers and flame retardants, or the molecular chains of thermosetting polyester materials contain intrinsic phosphorus-containing segments to achieve efficient flame retardancy of unsaturated polyester materials. The introduction of these additives and phosphorus-containing structures will affect the catalytic degradation efficiency of traditional hydrolysis, alcoholysis, aminolysis, and acidolysis systems. At the same time, phosphorus-containing flame-retardant unsaturated polyester materials have high value, and the development of degradation and recycling technologies for them is of great significance. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for recycling thermosetting flame-retardant polyester composites, which can degrade thermosetting phosphorus-containing flame-retardant polyester composites and reuse the recovered products.

[0005] To achieve the above purpose, the present invention provides a method for recycling thermosetting flame-retardant polyester composites, including the following steps: Step S1, preparing a thermosetting phosphorus-containing flame-retardant polyester composite; Step S2, degrading the thermosetting phosphorus-containing flame-retardant polyester composite to obtain the product after degradation of the thermosetting phosphorus-containing flame-retardant polyester composite; Step S3, separating and recovering the product after degradation of the thermosetting phosphorus-containing flame-retardant polyester composite to obtain the recovered product; Step S4: Reuse the recycled products.

[0006] Preferably, step S1 is specifically as follows: Step S11: Weigh maleic anhydride, phthalic anhydride, 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid containing a +1 phosphorus oxidation state structure, propylene glycol, and p-benzoquinone and mix them evenly; among them, the molar ratio of maleic anhydride, phthalic anhydride, 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid, propylene glycol, and p-benzoquinone is 1:(0 - 0.5):(0.5 - 1):(2 - 2.4):0.001; Step S12: Slowly raise the temperature of the reaction system to 170°C under a nitrogen atmosphere; Step S13: After two hours, raise the reaction temperature to 180°C and maintain it for 4 hours; when the acid value is lower than 40 mg KOH / g, terminate the reaction to obtain a thermosetting phosphorus-containing flame-retardant polyester prepolymer; Step S14: Weigh styrene and a zirconium phosphate inorganic lamellar filler loaded with phosphotungstic acid containing a +5 phosphorus oxidation state structure and mix them evenly, then add the thermosetting phosphorus-containing flame-retardant polyester prepolymer and mix evenly to obtain a mixed resin; among them, the mass ratio of styrene, the zirconium phosphate inorganic lamellar filler to the thermosetting phosphorus-containing flame-retardant polyester prepolymer is 1:(0.05 - 0.1):1.5; Step S15: Add benzoyl peroxide to the mixed resin and mix evenly, apply it on the surface of the fiberglass cloth, then stack several layers of fiberglass cloth neatly, and hot press it at 70 - 130°C and a pressure of 15 MPa until it is completely cured to obtain a thermosetting phosphorus-containing flame-retardant polyester composite material; among them, the mass ratio of the mixed resin to benzoyl peroxide is 1:(0.0015 - 0.003).

[0007] Preferably, step S2 is specifically as follows: Step S21: Place the thermosetting phosphorus-containing flame-retardant polyester composite material in a formic acid or glacial acetic acid solution dispersed with a 4 - 10 wt% acid catalyst to obtain a dispersion; Step S22: Pour the dispersion into a reaction kettle and react at a temperature of 80 - 160°C for a reaction time of 1 - 10 h to obtain the product after degradation of the thermosetting phosphorus-containing flame-retardant polyester composite material.

[0008] Preferably, in step S21, the addition ratio of the thermosetting phosphorus-containing flame-retardant polyester composite material to the formic acid or glacial acetic acid solution is 1 g:(5 - 20) mL; Among them, the acid catalyst includes but is not limited to phosphomolybdic acid and phosphotungstic acid.

[0009] Preferably, step S3 is specifically as follows: Step S31: Separate and purify the products obtained after the degradation of the thermosetting phosphorus-containing flame-retardant polyester composite material to recover the raw materials; Filter the products obtained after the degradation of the thermosetting phosphorus-containing flame-retardant polyester composite material to separate the parts soluble and insoluble in the degradation solution in the degradation system; Among them, the part insoluble in the degradation solution is zirconium phosphate lamellae and fiberglass cloth, and the zirconium phosphate lamellae and fiberglass cloth are separated by flushing with water; Step S32: Add an equal volume of water to the part soluble in the degradation solution, filter to obtain the remaining filtrate and the part insoluble in water, and collect the part insoluble in water to obtain styrene-maleic anhydride copolymer; Step S33: Separate the formic acid-aqueous solution or acetic acid-aqueous solution from the remaining filtrate by one separation method among rotary evaporation, evaporation, and distillation to obtain a mixture of phosphotungstic acid and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid.

[0010] Preferably, step S4 is specifically as follows: Step S41: Prepare a polymer material using the styrene-maleic anhydride copolymer recovered in step S32 and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid recovered in step S33; Step S42: Add the zirconium phosphate lamellae recovered in step S31 to the polymer material to prepare a phosphorus-containing flame-retardant polymer material again.

[0011] Preferably, in step S41, the preparation of the polymer material is specifically by subjecting the styrene-maleic anhydride copolymer and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid to an esterification reaction with polyether polyol and polyester polyol, or by subjecting the styrene-maleic anhydride copolymer and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid to a condensation reaction with isocyanate; Among them, the isocyanate includes but is not limited to 1,5-pentanediisocyanate and dimer diisocyanate.

[0012] Therefore, the present invention adopts the above-mentioned method for the recycling and reuse of thermosetting flame-retardant polyester composite materials. This method can degrade the thermosetting phosphorus-containing flame-retardant polyester composite material and reuse the recovered products.

[0013] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0014] Figure 1This is the flowchart of step S3 in the embodiment of the recycling method for a thermosetting flame-retardant polyester composite material of the present invention; Figure 2 This is the microscopic scanning electron microscope image of the fiberglass cloth in the embodiment of the recycling method for a thermosetting flame-retardant polyester composite material of the present invention, with a scale of 100 μM; Figure 3 This is the XRD pattern of the recovered zirconium phosphate lamella in the embodiment of the recycling method for a thermosetting flame-retardant polyester composite material of the present invention; Figure 4 This is the infrared spectrum of styrene-maleic anhydride copolymer in the embodiment of the recycling method for a thermosetting flame-retardant polyester composite material of the present invention; Figure 5 This is for solid 3 in the embodiment of the recycling method for a thermosetting flame-retardant polyester composite material of the present invention 31 P-NMR spectrum; Figure 6 This is the heat release rate curve of the recycled product for preparing a flame-retardant polymer material in the embodiment of the recycling method for a thermosetting flame-retardant polyester composite material of the present invention. Detailed implementation manners

[0015] The technical solutions of the present invention will be further described below through the accompanying drawings and embodiments.

[0016] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs.

[0017] A recycling method for a thermosetting flame-retardant polyester composite material includes the following steps: Step S1: Prepare a thermosetting phosphorus-containing flame-retardant polyester composite material; Step S2: Degrade the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain the degraded product of the thermosetting phosphorus-containing flame-retardant polyester composite material; Step S3: Separate and recover the degraded product of the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a recovered product; Step S4: Reuse the recovered product.

[0018] Embodiment A recycling method for a thermosetting flame-retardant polyester composite material includes the following steps: Step S1: Prepare a thermosetting phosphorus-containing flame-retardant polyester composite material.

[0019] Step S11: Weigh 16.1 g of maleic anhydride, 2.9 g of phthalic anhydride, 50.3 g of 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid with a +1 phosphorus oxidation state structure, 32.6 g of propylene glycol, and 0.015 g of p-benzoquinone, and mix them evenly.

[0020] Step S12: Slowly heat the reaction system to 170 °C under a nitrogen atmosphere.

[0021] Step S13: After two hours, raise the reaction temperature to 180 °C and maintain it for 4 hours. When the acid value is lower than 40 mg KOH / g, terminate the reaction to obtain a thermosetting phosphorus-containing flame-retardant polyester prepolymer.

[0022] Step S14: Weigh 60 g of styrene and 4.5 g of zirconium phosphate inorganic lamellar filler loaded with phosphotungstic acid with a +5 phosphorus oxidation state structure, mix them evenly, and then add the thermosetting phosphorus-containing flame-retardant polyester prepolymer and mix evenly to obtain a mixed resin.

[0023] Step S15: Add 3.0 g of benzoyl peroxide to the mixed resin and mix evenly. Apply it on the surface of a glass fiber cloth, then stack several layers of glass fiber cloth neatly, and hot press at 100 °C and a pressure of 15 MPa until it is completely cured to obtain a thermosetting phosphorus-containing flame-retardant polyester composite material.

[0024] Step S2: Degrade the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain the product after degradation of the thermosetting phosphorus-containing flame-retardant polyester composite material.

[0025] Step S21: Place 1 g of the thermosetting phosphorus-containing flame-retardant polyester composite material in 10 mL of a formic acid or glacial acetic acid solution containing 7 wt% phosphomolybdic acid to obtain a dispersion.

[0026] Step S22: Pour the dispersion into a reaction kettle, react at a temperature of 120 °C for 5 h to obtain the product after degradation of the thermosetting phosphorus-containing flame-retardant polyester composite material.

[0027] Step S3: As Figure 1 shown, separate and recover the product after degradation of the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a recovered product.

[0028] Step S31: Filter the product obtained after degradation of the thermosetting phosphorus-containing flame-retardant polyester composite material to separate the part soluble and insoluble in the degradation solution in the degradation system.

[0029] Among them, the part insoluble in the degradation solution (solid 1) is zirconium phosphate lamellae and glass fiber cloth, and the zirconium phosphate lamellae and glass fiber cloth are separated by washing with water.

[0030] As Figure 2As shown, after the degradation test, the fiberglass cloth in the composite material was degraded into single fiberglass.

[0031] As Figure 3 shown, there is only an obvious diffraction peak at 2θ = 11.7°, corresponding to the (002) crystal plane of zirconium phosphate, indicating that the original zirconium phosphate substance can be recovered through the degradation process in this embodiment.

[0032] Step S32: The part dissolved in the degradation solution (liquid 1) is a formic acid or glacial acetic acid filtrate. Add an equal volume of water to the formic acid or glacial acetic acid filtrate, filter to obtain the remaining filtrate (liquid 2) and the part insoluble in water, and collect the part insoluble in water to obtain styrene-maleic acid copolymer (solid 2).

[0033] As Figure 4 shown, through the infrared spectrum analysis of solid 2, it is shown that it is a styrene-maleic acid copolymer.

[0034] Step S33: The remaining filtrate (liquid 2) is separated by rotary evaporation of the formic acid-aqueous solution or acetic acid-aqueous solution to obtain a mixture of phosphotungstic acid and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid (solid 3), as Figure 5 shown.

[0035] Step S4: Reuse the recovered products.

[0036] Step S41: Prepare a polymer material from the styrene-maleic acid copolymer recovered in step S32 and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid recovered in step S33.

[0037] Specifically, the preparation of the polymer material is carried out by the esterification reaction of styrene-maleic acid copolymer with 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid and polyether polyol or polyester polyol, or by the condensation reaction between styrene-maleic acid copolymer and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid and isocyanate.

[0038] Step S42: Add the zirconium phosphate lamella recovered in step S31 to the polymer material to prepare a phosphorus-containing flame-retardant polymer material again. As Figure 6 shown, the recycled phosphorus-containing substances such as 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid and zirconium phosphate lamella make the phosphorus-containing flame-retardant polymer material have a lower peak value of heat release rate.

[0039] Therefore, the present invention adopts the above-mentioned method for recycling and reusing thermosetting flame-retardant polyester composites, which can degrade thermosetting phosphorus-containing flame-retardant polyester composites and reuse the recovered products thereof.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for recycling and reusing a thermosetting flame-retardant polyester composite material, characterized in that, It includes the following steps: Step S1: Prepare a thermosetting phosphorus-containing flame-retardant polyester composite material; Step S2: Degrade the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain the degraded product of the thermosetting phosphorus-containing flame-retardant polyester composite material; Step S3: Separate and recover the degraded product of the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a recovered product; Step S4: Reuse the recovered product.

2. The recycling method for a thermosetting flame-retardant polyester composite material according to claim 1, characterized in that, Specifically, step S1 is as follows: Step S11: Weigh maleic anhydride, phthalic anhydride, 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid with a +1 phosphorus oxidation state structure, propylene glycol, and p-benzoquinone and mix them evenly; among them, the molar ratio of maleic anhydride, phthalic anhydride, 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid, propylene glycol, and p-benzoquinone is 1:(0 - 0.5):(0.5 - 1):(2 - 2.4):0.001; Step S12: Slowly raise the temperature of the reaction system to 170 °C under a nitrogen atmosphere; Step S13: After two hours, raise the reaction temperature to 180 °C and maintain it for 4 hours; when the acid value is lower than 40 mg KOH / g, terminate the reaction to obtain a thermosetting phosphorus-containing flame-retardant polyester prepolymer; Step S14: Weigh styrene and a zirconium phosphate inorganic lamellar filler loaded with phosphotungstic acid with a +5 phosphorus oxidation state structure and mix them evenly, and then add the thermosetting phosphorus-containing flame-retardant polyester prepolymer and mix them evenly to obtain a mixed resin; among them, the mass ratio of styrene, zirconium phosphate inorganic lamellar filler to the thermosetting phosphorus-containing flame-retardant polyester prepolymer is 1:(0.05 - 0.1):1.5; Step S15: Add benzoyl peroxide to the mixed resin and mix it evenly, apply it on the surface of the glass fiber cloth, then stack several layers of glass fiber cloth neatly, and hot press it at 70 - 130 °C and a pressure of 15 MPa until it is completely cured to obtain a thermosetting phosphorus-containing flame-retardant polyester composite material; among them, the mass ratio of the mixed resin to benzoyl peroxide is 1:(0.0015 - 0.003).

3. A method for recycling and reusing a thermosetting flame-retardant polyester composite according to claim 1, characterized in that, Specifically, step S2 is as follows: Step S21: Place the thermosetting phosphorus-containing flame-retardant polyester composite material in a formic acid or glacial acetic acid solution dispersed with a 4 - 10 wt% acid catalyst to obtain a dispersion; Step S22: Pour the dispersion into a reaction kettle and react at a temperature of 80 - 160 °C for a reaction time of 1 - 10 h to obtain the degraded product of the thermosetting phosphorus-containing flame-retardant polyester composite material.

4. A method for recycling and reusing a thermosetting flame-retardant polyester composite according to claim 3, characterized in that: In step S21, the addition ratio of the thermosetting phosphorus-containing flame-retardant polyester composite material to the formic acid or glacial acetic acid solution is 1 g:(5 - 20) mL; Among them, the acid catalyst includes but is not limited to phosphomolybdic acid and phosphotungstic acid.

5. A method for recycling and reusing a thermosetting flame-retardant polyester composite according to claim 1, characterized in that, Specifically, step S3 is as follows: Step S31: Filter the obtained degraded product of the thermosetting phosphorus-containing flame-retardant polyester composite material to separate the part soluble and insoluble in the degradation solution in the degradation system; Among them, the part insoluble in the degradation solution is zirconium phosphate lamellae and glass fiber cloth, and the zirconium phosphate lamellae and glass fiber cloth are separated by washing with water; Step S32: Add an equal volume of water to the part dissolved in the degradation solution, filter to obtain the remaining filtrate and the part insoluble in water, and collect the part insoluble in water to obtain the styrene-maleic acid copolymer. Step S33: Separate the formic acid-aqueous solution or acetic acid-aqueous solution from the remaining filtrate by one of the separation methods of rotary evaporation, evaporation, and distillation to obtain a mixture of phosphotungstic acid and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid.

6. A method for recycling and reusing a thermosetting flame-retardant polyester composite according to claim 5, characterized in that, Step S4 specifically includes: Step S41: Prepare a polymer material using the styrene-maleic acid copolymer recovered in Step S32 and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid recovered in Step S33. Step S42: Add the zirconium phosphate lamella recovered in Step S31 to the polymer material to prepare a phosphorus-containing flame-retardant polymer material again.

7. A method for recycling and reusing a thermosetting flame-retardant polyester composite according to claim 6, characterized in that: In Step S41, the preparation of the polymer material specifically involves an esterification reaction of the styrene-maleic acid copolymer and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid with polyether polyol and polyester polyol, or a condensation reaction between the styrene-maleic acid copolymer and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid and isocyanate. Among them, the isocyanate includes but is not limited to 1,5-pentane diisocyanate and dimer diisocyanate.

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