A recycling method for thermosetting flame-retardant polyester composite materials

Abstract

The present invention belongs to the field of recycling and reuse of polyester materials, and specifically discloses a method for recycling and reuse of thermosetting flame-retardant polyester composite materials, comprising the following steps: Step S1, preparing a thermosetting phosphorus-containing flame-retardant polyester composite material; Step S2, degrading the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material; Step S3, separating and recovering the degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a recovered product; and Step S4, reusing the recovered product. The present invention adopts the above-mentioned method for recycling and reuse of thermosetting flame-retardant polyester composite materials, which can degrade the thermosetting phosphorus-containing flame-retardant polyester composite material and reuse the recovered product.

Description

Technical Field

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

[0002] As one of the world's most produced synthetic polymers, polyester has been widely used in a wide range of fields, including textiles, packaging, construction, and electronics. Thermoplastic polyesters, represented by polyethylene terephthalate (PET), have an annual production volume exceeding 80 million tons. Thermosetting polyesters (such as unsaturated polyester resins), due to their excellent mechanical properties and corrosion resistance, have an annual consumption of over 12 million tons in composite materials, automotive parts, and other fields. Therefore, the development of efficient recycling technologies has become a key research priority in the global chemical industry. While thermoplastic polyesters like PET are relatively easy to recycle during degradation, thermosetting materials like unsaturated polyesters, such as unsaturated polyesters, form a dense cross-linked network (cross-linking degree >85%) after curing, which is difficult to destroy with conventional solvents or thermodynamic methods. This makes recycling and reuse more challenging. Disposing of discarded unsaturated polyesters at the end of their useful life has become a pressing issue.

[0003] At the same time, current research on the degradation and recycling of thermosetting polyester materials often focuses on pure polyester materials, ignoring the impact of additives and intrinsic functional structures in thermosetting polyester materials in actual applications. Actual waste often contains 30%-50% additives such as glass fiber and flame retardants, or the thermosetting polyester material molecular chain contains intrinsic phosphorus-containing segments to achieve efficient flame retardancy in 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. Furthermore, the high value of phosphorus-containing flame-retardant unsaturated polyester materials makes the development of degradation and recycling technologies for them of great significance. Summary of the Invention

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

[0005] To achieve the above object, the present invention provides a method for recycling a thermosetting flame-retardant polyester composite material, comprising the following steps:

[0006] Step S1, preparing a thermosetting phosphorus-containing flame-retardant polyester composite material;

[0007] Step S2, degrading the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material;

[0008] Step S3, separating and recovering degradation products of the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a recovered product;

[0009] Step S4: Reusing the recovered product.

[0010] Preferably, step S1 is specifically as follows:

[0011] Step S11, weighing maleic anhydride, phthalic anhydride, 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid containing a +1 phosphorus oxidation state structure, propylene glycol, and p-benzoquinone and uniformly mixing; wherein the molar ratio of maleic anhydride, phthalic anhydride, 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid, propylene glycol, and p-benzoquinone is 1:(0-0.5):(0.5-1):(2-2.4):0.001;

[0012] Step S12, slowly heating the reaction system to 170° C. under a nitrogen atmosphere;

[0013] Step S13: After two hours, the reaction temperature is raised to 180° C. and maintained for 4 hours; when the acid value is lower than 40 mg KOH / g, the reaction is terminated to obtain a thermosetting phosphorus-containing flame-retardant polyester prepolymer;

[0014] Step S14, weighing styrene and a zirconium phosphate inorganic lamellar filler loaded with phosphotungstic acid containing a +5 phosphorus oxidation state structure, mixing them evenly, and then adding a thermosetting phosphorus-containing flame-retardant polyester prepolymer and mixing them evenly to obtain a mixed resin; wherein the mass ratio of styrene, zirconium phosphate inorganic lamellar filler to thermosetting phosphorus-containing flame-retardant polyester prepolymer is 1:(0.05-0.1):1.5;

[0015] Step S15: Add dibenzoyl peroxide to the mixed resin, mix evenly, and apply it on the surface of the glass fiber cloth. Then, stack several layers of glass fiber cloth neatly, and hot press at 70-130° C. and 15 MPa pressure until completely cured, thereby obtaining a thermosetting phosphorus-containing flame-retardant polyester composite material. The mass ratio of the mixed resin to dibenzoyl peroxide is 1:(0.0015-0.003).

[0016] Preferably, step S2 is specifically as follows:

[0017] Step S21, dispersing the thermosetting phosphorus-containing flame-retardant polyester composite material in a formic acid or glacial acetic acid solution containing 4-10 wt% of an acid catalyst to obtain a dispersion;

[0018] Step S22: pouring the dispersion into a reaction kettle, reacting at a temperature of 80-160° C. for 1-10 hours, thereby obtaining a degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material.

[0019] 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;

[0020] The acid catalyst includes but is not limited to phosphomolybdic acid and phosphotungstic acid.

[0021] Preferably, step S3 is specifically as follows:

[0022] Step S31, separating and purifying the degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material to recover the raw material;

[0023] filtering the degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material to separate the portion soluble in the degradation solution and the portion insoluble in the degradation solution;

[0024] The parts that are insoluble in the degradation solution are the zirconium phosphate sheet and the glass fiber cloth, which are separated by washing with water.

[0025] Step S32, adding an equal volume of water to the portion dissolved in the degradation solution, filtering to obtain the remaining filtrate and the water-insoluble portion, and collecting the water-insoluble portion to obtain a styrene-maleic acid copolymer;

[0026] Step S33: Separate the formic acid-water solution or the acetic acid-water solution from the remaining filtrate by rotary evaporation, evaporation, or distillation to obtain a mixture of phosphotungstic acid and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphine-6-yl)methyl]succinic acid.

[0027] Preferably, step S4 is specifically as follows:

[0028] Step S41, preparing a polymer material using the styrene-maleic acid copolymer recovered in step S32 and the 2-[(6-oxydibenzo[c,e][1,2]oxaphosphine-6-yl)methyl]succinic acid recovered in step S33;

[0029] Step S42: adding the zirconium phosphate flakes recovered in step S31 to the polymer material to prepare the phosphorus-containing flame-retardant polymer material again.

[0030] Preferably, in step S41, preparing the polymer material is specifically carried out by esterification reaction of styrene-maleic acid copolymer with 2-[(6-oxydibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid and polyether polyol or polyester polyol, or by condensation reaction of styrene-maleic acid copolymer with 2-[(6-oxydibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid and isocyanate;

[0031] The isocyanate includes but is not limited to 1,5-pentamethylene diisocyanate and dimer diisocyanate.

[0032] Therefore, the present invention adopts the above-mentioned method for recycling and reusing thermosetting flame-retardant polyester composite materials, which can degrade the thermosetting phosphorus-containing flame-retardant polyester composite materials and reuse the recovered products.

[0033] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of step S3 in an embodiment of a method for recycling and reusing a thermosetting flame-retardant polyester composite material of the present invention;

[0035] Figure 2 This is a microscopic scanning electron microscope image of a glass fiber cloth in an embodiment of a method for recycling and reusing a thermosetting flame-retardant polyester composite material of the present invention, with a scale of 100 μM;

[0036] Figure 3 This is an XRD pattern of the zirconium phosphate flakes recovered in an embodiment of a method for recycling and reusing a thermosetting flame-retardant polyester composite material of the present invention;

[0037] Figure 4 This is an infrared spectrum of a styrene-maleic acid copolymer in an embodiment of a method for recycling and reusing a thermosetting flame-retardant polyester composite material of the present invention;

[0038] Figure 5 The solid 3 in the embodiment of the method for recycling thermosetting flame retardant polyester composite material of the present invention is 31 P-NMR spectrum;

[0039] Figure 6 This is a heat release rate curve of a flame-retardant polymer material prepared from a recovered product in an embodiment of a method for recycling and reusing a thermosetting flame-retardant polyester composite material of the present invention. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0041] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0042] A method for recycling a thermosetting flame-retardant polyester composite material comprises the following steps:

[0043] Step S1, preparing a thermosetting phosphorus-containing flame-retardant polyester composite material;

[0044] Step S2, degrading the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material;

[0045] Step S3, separating and recovering degradation products of the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a recovered product;

[0046] Step S4: Reusing the recovered product.

[0047] Example

[0048] A method for recycling a thermosetting flame-retardant polyester composite material comprises the following steps:

[0049] Step S1: preparing a thermosetting phosphorus-containing flame-retardant polyester composite material.

[0050] Step S11, weighing 16.1 g of maleic anhydride, 2.9 g of phthalic anhydride, 50.3 g of 2-[(6-oxodibenzo[c,e][1,2]oxaphosphine-6-yl)methyl]butanedioic acid containing a +1 phosphorus oxidation state structure, 32.6 g of propylene glycol and 0.015 g of p-benzoquinone and mixing them evenly.

[0051] Step S12: slowly heating the reaction system to 170° C. under a nitrogen atmosphere.

[0052] Step S13: After two hours, the reaction temperature is raised to 180° C. and maintained for 4 hours. When the acid value is lower than 40 mg KOH / g, the reaction is terminated to obtain a thermosetting phosphorus-containing flame-retardant polyester prepolymer.

[0053] Step S14: Weigh 60 g of styrene and 4.5 g of zirconium phosphate inorganic lamellar filler loaded with phosphotungstic acid containing a +5 phosphorus oxidation state structure, mix them evenly, then add thermosetting phosphorus-containing flame-retardant polyester prepolymer and mix them evenly to obtain a mixed resin.

[0054] Step S15: Add 3.0 g of dibenzoyl peroxide to the mixed resin, mix evenly, and apply it on the surface of the 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 completely cured, thereby obtaining a thermosetting phosphorus-containing flame-retardant polyester composite material.

[0055] Step S2: Degrading the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material.

[0056] Step S21: 1 g of the thermosetting phosphorus-containing flame-retardant polyester composite material is dispersed in 10 mL of a formic acid or glacial acetic acid solution containing 7 wt % of phosphomolybdic acid to obtain a dispersion.

[0057] Step S22: pour the dispersion into a reactor and react at a temperature of 120° C. for 5 hours to obtain a degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material.

[0058] Step S3, as Figure 1 As shown, the degradation products of the thermosetting phosphorus-containing flame-retardant polyester composite material are separated and recovered to obtain a recycled product.

[0059] Step S31: filtering the degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material to separate the portion soluble in the degradation solution and the portion insoluble in the degradation solution.

[0060] The portion insoluble in the degradation solution (solid 1) is the zirconium phosphate sheet and the glass fiber cloth. The zirconium phosphate sheet and the glass fiber cloth are separated by washing with water.

[0061] like Figure 2 As shown in the figure, after the degradation test, the glass fiber cloth in the composite material was degraded into single glass fibers.

[0062] like Figure 3 As 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 material can be recovered through the degradation process in this example.

[0063] Step S32: The portion soluble in the degradation solution (liquid 1) is the formic acid or glacial acetic acid filtrate. An equal volume of water is added to the formic acid or glacial acetic acid filtrate, and the mixture is filtered to obtain the remaining filtrate (liquid 2) and the water-insoluble portion. The water-insoluble portion is collected to obtain the styrene-maleic acid copolymer (solid 2).

[0064] like Figure 4 As shown, the infrared spectrum analysis of solid 2 shows that it is a styrene-maleic acid copolymer.

[0065] Step S33: The remaining filtrate (liquid 2) is separated by rotary evaporation from formic acid-water solution or acetic acid-water solution to obtain a mixture of phosphotungstic acid and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphin-6-yl)methyl]butanedioic acid (solid 3). Figure 5 shown.

[0066] Step S4: Reusing the recovered product.

[0067] Step S41: preparing a polymer material by using the styrene-maleic acid copolymer recovered in step S32 and the 2-[(6-oxydibenzo[c,e][1,2]oxaphosphine-6-yl)methyl]succinic acid recovered in step S33.

[0068] The polymer material is prepared specifically by an esterification reaction between a styrene-maleic acid copolymer and 2-[(6-oxydibenzo[c,e][1,2]oxyphosphorin-6-yl)methyl]butanedioic acid and polyether polyol or polyester polyol, or by a condensation reaction between a styrene-maleic acid copolymer and 2-[(6-oxydibenzo[c,e][1,2]oxyphosphorin-6-yl)methyl]butanedioic acid and isocyanate.

[0069] Step S42: adding the zirconium phosphate flakes recovered in step S31 to the polymer material to prepare the phosphorus-containing flame-retardant polymer material again. Figure 6 As shown in the figure, the recycled phosphorus-containing substances such as 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid and zirconium phosphate sheets make the phosphorus-containing flame retardant polymer material have a lower peak heat release rate.

[0070] Therefore, the present invention adopts the above-mentioned method for recycling and reusing thermosetting flame-retardant polyester composite materials, which can degrade the thermosetting phosphorus-containing flame-retardant polyester composite materials and reuse the recovered products.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for recycling thermosetting flame-retardant polyester composite materials, characterized in that: The following steps are involved: Step S1, preparing a thermosetting phosphorus-containing flame-retardant polyester composite material; Step S11, weighing maleic anhydride, phthalic anhydride, 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid containing a +1 phosphorus oxidation state structure, propylene glycol, and p-benzoquinone and uniformly mixing; wherein the molar ratio of maleic anhydride, phthalic anhydride, 2-[(6-oxodibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid, propylene glycol, and p-benzoquinone is 1:(0-0.5):(0.5-1):(2-2.4):0.001; Step S12, slowly heating the reaction system to 170° C. under a nitrogen atmosphere; Step S13: After two hours, the reaction temperature is raised to 180° C. and maintained for 4 hours; when the acid value is lower than 40 mg KOH / g, the reaction is terminated to obtain a thermosetting phosphorus-containing flame-retardant polyester prepolymer; Step S14, weighing styrene and a zirconium phosphate inorganic lamellar filler loaded with phosphotungstic acid containing a +5 phosphorus oxidation state structure, mixing them evenly, and then adding a thermosetting phosphorus-containing flame-retardant polyester prepolymer and mixing them evenly to obtain a mixed resin; wherein the mass ratio of styrene, zirconium phosphate inorganic lamellar filler to thermosetting phosphorus-containing flame-retardant polyester prepolymer is 1:(0.05-0.1):1.5; Step S15: adding dibenzoyl peroxide to the mixed resin and mixing evenly, applying the mixture to the surface of the glass fiber cloth, then stacking several layers of the glass fiber cloth neatly, and hot pressing at 70-130° C. and a pressure of 15 MPa until the mixture is completely cured, thereby obtaining a thermosetting phosphorus-containing flame-retardant polyester composite material; wherein the mass ratio of the mixed resin to dibenzoyl peroxide is 1:(0.0015-0.003); Step S2, degrading the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material; Step S21, dispersing the thermosetting phosphorus-containing flame-retardant polyester composite material in a formic acid or glacial acetic acid solution containing 4-10 wt% of an acid catalyst to obtain a dispersion; The addition ratio of thermosetting phosphorus-containing flame-retardant polyester composite material to formic acid or glacial acetic acid solution is 1g: (5-20)mL; Wherein, the acid catalyst is phosphomolybdic acid or phosphotungstic acid; Step S22, pouring the dispersion into a reactor, reacting at a temperature of 80-160° C. for 1-10 hours, thereby obtaining a degradation product of a thermosetting phosphorus-containing flame-retardant polyester composite material; Step S3, separating and recovering degradation products of the thermosetting phosphorus-containing flame-retardant polyester composite material to obtain a recovered product; Step S4: Reusing the recovered product.

2. The method for recycling thermosetting flame-retardant polyester composite materials according to claim 1, characterized in that: Step S3 is specifically as follows: Step S31, filtering the degradation product of the thermosetting phosphorus-containing flame-retardant polyester composite material to separate the portion soluble in the degradation solution and the portion insoluble in the degradation solution; The parts that are insoluble in the degradation solution are the zirconium phosphate sheet and the glass fiber cloth, which are separated by washing with water. Step S32, adding an equal volume of water to the portion dissolved in the degradation solution, filtering to obtain the remaining filtrate and the water-insoluble portion, and collecting the water-insoluble portion to obtain a styrene-maleic acid copolymer; Step S33: removing the formic acid-water solution or the acetic acid-water solution from the remaining filtrate by rotary evaporation to obtain a mixture of phosphotungstic acid and 2-[(6-oxodibenzo[c,e][1,2]oxaphosphine-6-yl)methyl]succinic acid.

3. The method for recycling thermosetting flame-retardant polyester composite materials according to claim 2, characterized in that: Step S4 is specifically as follows: Step S41, preparing a polymer material using the styrene-maleic acid copolymer recovered in step S32 and the 2-[(6-oxydibenzo[c,e][1,2]oxaphosphine-6-yl)methyl]succinic acid recovered in step S33; Step S42: adding the zirconium phosphate flakes recovered in step S31 to the polymer material to prepare the phosphorus-containing flame-retardant polymer material again.

4. The method for recycling thermosetting flame-retardant polyester composite materials according to claim 3, characterized in that: In step S41, the polymer material is prepared by esterifying styrene-maleic acid copolymer, 2-[(6-oxydibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid with polyether polyol or polyester polyol, or condensing styrene-maleic acid copolymer, 2-[(6-oxydibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid with isocyanate; The isocyanate includes but is not limited to 1,5-pentamethylene diisocyanate and dimer diisocyanate.

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