Method for preparing photocurable 3D printing material from waste PETG and application of photocurable 3D printing material

Abstract

The invention relates to the technical field of waste polyester recovery and high value-added polyester synthesis, and discloses a method for preparing a photocurable 3D printing material from waste PETG and application, the method comprises the following steps: (1) adding an alcoholysis agent, ethylene glycol and 1, 4-cyclohexanedimethanol into waste PETG powder, introducing nitrogen, and carrying out an alcoholysis reaction to obtain an oligomer; (2) adding maleic acid or maleic anhydride into the oligomer, and carrying out esterification / ester exchange reaction; adding a polycondensation catalyst, a polymerization inhibitor and an auxiliary agent, and carrying out polycondensation reaction; after the reaction is finished, granulating and drying to obtain polyester chips; and (3) mixing the polyester chips with a lubricant and an ultraviolet light initiator, and then carrying out melt extrusion. The unsaturated monomer is introduced into a PETG system, so that regeneration and high-value utilization of PETG waste are realized, ultraviolet curing in the 3D printing process can be realized, and the problems that a printed piece is easy to warp and shrink and the like in the printing process are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of waste polyester recycling and high-value-added polyester synthesis, and in particular to a method for preparing a photocurable 3D printing material from waste PETG and its application. Background Art

[0002] Poly(ethylene terephthalate-1,4-cyclohexanedimethanol ester) (PETG) is a transparent material with low crystallinity, having excellent optical properties, good toughness and impact resistance, being environmentally friendly and easy to process and form, and being widely applied in fields such as transparent bottles, sheets, plates, pipes and films. However, with the wide use of PETG, hundreds of thousands of tons of PETG waste enter the environment every year, and the environmental protection situation is severe. Therefore, the related research work on the efficient and high-value recycling of waste PETG is extremely urgent.

[0003] PETG has good processability and a low heat distortion temperature, and has been applied as a 3D printing wire, which can make up for the problems of high shrinkage rate of ABS printing consumables and insufficient toughness of polylactic acid materials. However, during the printing process of PETG, due to its high viscosity, it is easy to adhere to the nozzle, and the material at the nozzle will be printed on the printed part along with the extruded material, easily causing wire drawing, faulting and misalignment of the printed part, seriously affecting the printing accuracy. In addition, PETG has a high melt strength, poor fluidity, and is not easy to crystallize, and the printed part is prone to warping, curling and deformation, and the shape of the printed part is not easy to be quickly fixed.

[0004] Chinese invention patent with the publication number of CN113929886A discloses a long-chain branched PETG copolyester and its preparation method, in which a multi-functional branching agent is added during the synthesis process to carry out copolymerization with PETG monomers, which can improve the melt strength of the PETG copolyester. However, the degree of crosslinking of the branching agent is uncontrollable, and it is extremely easy to form a gel-like crosslinked network, affecting the printing accuracy.

[0005] Chinese invention patent with the publication number of CN113773616A discloses a PETG-G material for high-strength and low-shrinkage 3D printer consumables and its preparation method, mainly by blending PETG with PBAT and ABS resins to improve the printing wire drawing property, printing accuracy and reduce the printing temperature. However, PBAT and ABS resins have good crystallinity, and the blended wire has a certain crystallinity, and the transparency of the printed part is relatively low.

[0006] Chinese invention patent with the publication number of CN104559088A discloses a modified composite material suitable for 3D printing and its preparation method, by adding a thermoplastic elastomer to blend with PETG, and maleic anhydride as a compatibilizer to improve the toughness of the blend. However, the addition of maleic anhydride easily causes a gel structure to appear in the system, and the melt fluidity becomes poor, affecting the printing accuracy. Summary of the Invention

[0007] In order to solve the technical problems of high-value recycling of PETG nozzle materials and easy warping and shrinkage of printed parts in the 3D printing process using PETG as the material, the present invention provides a method for preparing light-curable 3D printing materials from waste PETG and application thereof, wherein unsaturated monomers are introduced into the PETG system, and an inhibitor is added in the polycondensation stage to protect the unsaturated bonds, and an initiator and a lubricant are added in the wire forming stage, so that ultraviolet curing can be achieved in the 3D printing process, and problems such as easy warping and shrinkage of printed parts can be avoided, thereby realizing the preparation of light-curable 3D printing PETG wire from PETG nozzle materials.

[0008] The purpose of the present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing a photocurable 3D printing material from waste PETG, comprising the following steps: (1) adding an alcoholysis agent, ethylene glycol, and 1,4-cyclohexanedimethanol to waste PETG powder, passing nitrogen gas, and performing alcoholysis reaction to obtain oligomers; (2) adding maleic acid or maleic anhydride to the oligomer to carry out esterification / ester exchange reaction; then adding a polycondensation catalyst, an inhibitor and an auxiliary agent to carry out a polycondensation reaction; after the reaction is completed, pelletizing and drying to obtain polyester chips; (3) The polyester chips are mixed with a lubricant and an ultraviolet light initiator, and then melt-extruded to obtain a photocurable 3D printing material.

[0009] Preferably, in step (1), the mass ratio of ethylene glycol to waste PETG powder is 1-3:1; the mass ratio of 1,4-cyclohexanedimethanol to waste PETG powder is 10-15:100.

[0010] Preferably, in step (1), the alcoholysis agent is one or more of titanium glycolate, cobalt acetate, cobalt acetate tetrahydrate, zinc acetate and zinc acetate dihydrate; and the amount of the alcoholysis agent added is 200-5000ppm based on the mass of the waste PETG powder.

[0011] Preferably, in step (1), the temperature of the alcoholysis reaction is 170-280° C., the nitrogen pressure condition is 50-150 kPa, and the reaction time is 1-8 h.

[0012] The invention accelerates the alcoholysis rate, reduces the reaction time and reduces the energy consumption by performing alcoholysis on ethylene glycol and CHDM in waste PETG powder under the protection condition of high-pressure nitrogen.

[0013] Preferably, in step (2), the mass ratio of maleic acid or maleic anhydride to waste PETG powder is 5-25:100; more preferably, the mass ratio of maleic acid or maleic anhydride to waste PETG powder is 10-25:100.

[0014] Preferably, in step (2), the temperature of the esterification / transesterification reaction is 200-240 °C, the nitrogen pressure condition is 50-150 kPa, the reaction time is 1-6 h, and part of ethylene glycol or water is fractionated out during the reaction.

[0015] Preferably, in step (2), the polycondensation catalyst includes one or more of antimony trioxide, antimony glycolate, tetrabutyl titanate, tetraisopropyl titanate, titanium glycolate, titanium diglycolate, titanium citrate, and titanium lactate; the addition amount of titanium or antimony element in the polycondensation catalyst is 4-200 ppm based on the mass of the waste PETG powder.

[0016] Preferably, in step (2), the polymerization inhibitor includes one or more of tert-butylhydroquinone and hydroquinone; the addition amount of the polymerization inhibitor is 50-150 ppm based on the mass of the waste PETG powder.

[0017] Preferably, in step (2), the additives include stabilizers, antioxidants, and colorants.

[0018] Preferably, the stabilizer includes one or more of hypophosphorous acid, phosphorous acid, phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, trimethyl phosphite, triphenyl phosphite, and triethyl phosphonoacetate; the addition amount of phosphorus element in the stabilizer is 4-50 ppm based on the mass of the waste PETG powder.

[0019] Preferably, the antioxidant includes one or more of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphite, distearyl pentaerythritol diphosphite, and N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hexanediamine; the addition amount of the antioxidant is 20-1500 ppm based on the mass of the waste PETG powder.

[0020] Preferably, the colorant includes organic anthraquinone colorants; the addition amount of the colorant is 0.2-20 ppm based on the mass of the waste PETG powder.

[0021] Preferably, in step (2), the polycondensation reaction is as follows: first, react at 240-260 °C and 1-10 kPa in a low vacuum environment for 1 h; then, react at 260-290 °C and 10-100 Pa in a high vacuum environment for 1-4 h.

[0022] Preferably, in step (3), the polyester chips are dried to a water content of less than 500 ppm.

[0023] Preferably, in step (3), the lubricant includes one or more of stearic acid, sodium stearate, calcium stearate, potassium stearate, magnesium stearate, zinc stearate, aluminum stearate, and barium stearate; the addition amount of the lubricant is 100 - 3000 ppm of the mass of the waste PETG powder.

[0024] Preferably, in step (3), the ultraviolet light initiator includes one or more of benzophenone, 1 - hydroxycyclohexyl phenyl ketone, and 2,2 - dimethoxy - 2 - phenylacetophenone; the addition amount of the ultraviolet light initiator is 500 - 3000 ppm of the mass of the waste PETG powder.

[0025] Preferably, in step (3), the mixing time is 10 - 30 min.

[0026] Preferably, in step (3), the temperature of the melt extrusion is 180 - 230 °C.

[0027] In a second aspect, the present invention also provides an application of a photocurable 3D printing material in 3D printing. When using the photocurable 3D printing material for 3D printing, ultraviolet light irradiation is performed at the printing nozzle and on the printed part after printing is completed.

[0028] The ultraviolet light irradiation at the printing nozzle plays a role in preliminary shaping, preventing the deformation of the printed part caused by untimely cooling during printing or the adhesion of the nozzle material; the subsequent irradiation of the printed part in the ultraviolet light box is to crosslink all the crosslinking sites in the printed part to complete curing and improve the mechanical strength of the object.

[0029] Preferably, the temperature of the printing nozzle is controlled at 250 - 260 °C, the temperature of the heated base plate is controlled at 75 - 90 °C, and the printing speed is 30 - 60 mm / s.

[0030] Preferably, an ultraviolet light source is equipped at the printing nozzle for ultraviolet light irradiation, the power density of the ultraviolet light source is 100 - 120 W / cm 2 , the main wavelength is 365 nm; the printed part after printing is further irradiated with ultraviolet light in an ultraviolet light irradiation device, the ultraviolet lamp power of the ultraviolet light irradiation device is 1 - 3 kw, the power density is 120 - 140 W / cm 2 , the main wavelength is 365 nm, and the irradiation time is 2 - 4 min.

[0031] Compared with the prior art, the present invention has the following beneficial effects: (1) In the present invention, the raw materials are derived from waste PETG runner materials in a PETG molding factory, realizing the regeneration and high-value utilization of PETG waste and reducing carbon emissions.

[0032] (2) In the alcoholysis process of waste PETG in the present invention, CHDM is added. The highly active CHDM can increase the alcoholysis rate and make up for the reduction of CHDM units in PETG caused by the subsequent addition of unsaturated dibasic acids / anhydrides, avoiding the weakening of the properties of recycled PETG.

[0033] (3) In the present invention, unsaturated monomers are introduced into the PETG system. By adding a polymerization inhibitor to protect the unsaturated bonds during the polycondensation stage and adding a UV initiator and a lubricant during the wire forming stage, UV curing can be achieved during the 3D printing process, accelerating the forming speed of 3D printed parts, weakening the problems of easy warping, shrinkage, and adhesion of 3D printed parts, and at the same time, the introduction of a crosslinked structure further enhances the mechanical strength of 3D printed parts.

[0034] (4) The difference between the present invention and the related patents that directly add a branching agent during the polymerization stage is that unsaturated double bond dibasic acids / anhydrides are introduced during the PETG polymerization stage, and a UV initiator is introduced during the wire forming stage, which can effectively reduce the formation of crosslinking points during high-temperature polymerization and low-temperature processing, reduce the number of crosslinking points in PETG wire before 3D printing, and improve the melt fluidity. Specific Embodiments

[0035] The following specific examples are used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto.

[0036] Example 1 (1) Alcoholysis of waste PETG: Weigh 1500 g of waste PETG runner material powder after crushing, washing, and drying, and add it to a 5 L stainless steel reaction kettle. Then, add 500 ppm of zinc acetate dihydrate, 1500 g of ethylene glycol (100% of the mass of the waste PETG runner material powder), and 150 g of CHDM (10% of the mass of the waste PETG runner material powder) to the reaction kettle. Introduce nitrogen and heat, and react at 240 °C for 2 h under a nitrogen pressure condition of 100 kPa to obtain an alcoholysis solution.

[0037] (2) Esterification / transesterification reaction: After depressurization, add 375 g of maleic acid (25% of the mass of the waste PETG runner material powder) to the reaction kettle, stir evenly, and use a nitrogen three-way valve to release gas three times. Carry out the esterification / transesterification reaction at 240 °C and a nitrogen pressure condition of 150 kPa. Part of the ethylene glycol is fractionated out by the esterification tower, and the reaction time is 4 h.

[0038] (3) Polycondensation reaction: Add titanium glycol (Ti added in an amount of 20 ppm), triphenyl phosphate (P added in an amount of 15 ppm), 800 ppm antioxidant 1010, 400 ppm antioxidant 168, 5 ppm red and blue colorant, and 100 ppm hydroquinone, and first react in a low vacuum environment of 265°C and 8 kPa for 1 hour to remove excess ethylene glycol; then react in a high vacuum environment of 275°C and 30 Pa for 1.5 hours; after the polycondensation reaction is completed, break the vacuum with nitrogen, pressurize the material, cut into pellets underwater, and dry to obtain polyester chips.

[0039] (4) Wire forming: The polyester chips were dried at 70°C until the water content was less than 500 ppm, and then cooled to room temperature; 1500 ppm calcium stearate and 1000 ppm benzophenone were added to the dried polyester chips, mixed in a high-speed mixer for 20 min, and then added to a single-screw extruder for extrusion, wherein the temperature of each heating zone of the single-screw extruder was set to: 185°C for zone 1, 215°C for zone 2, 225°C for zone 3, 225°C for zone 4, and 225°C for zone 5, and the circulating cooling water temperature was 25°C, to obtain a PETG wire with a diameter of 1.75 mm±0.05 mm.

[0040] Example 2 (1) Alcoholysis of waste PETG: 1500 g of the waste PETG nozzle material powder after crushing, washing and drying was weighed and added into a 5L stainless steel reactor, and then 500 ppm of zinc acetate dihydrate, 1500 g of ethylene glycol (accounting for 100% of the mass of the waste PETG nozzle material powder), and 150 g of CHDM (accounting for 10% of the mass of the waste PETG nozzle material powder) were added into the reactor, and nitrogen was introduced and heated. The reaction was carried out at 240° C. under a nitrogen pressure of 100 kPa for 2 h to obtain an alcoholysis solution.

[0041] (2) Esterification / ester exchange reaction: After depressurization, 375 g of maleic acid (accounting for 25% of the mass of the waste PETG nozzle material powder) was added to the reactor and stirred evenly. The esterification / ester exchange reaction occurred at 240°C and 150 kPa nitrogen pressure using a three-way nitrogen release. Part of the ethylene glycol was distilled out of the esterification tower. The reaction time was 4 h.

[0042] (3) Polycondensation reaction: Add titanium glycol (Ti added in an amount of 20 ppm), triphenyl phosphate (P added in an amount of 15 ppm), 800 ppm antioxidant 1010, 400 ppm antioxidant 168, 5 ppm red and blue colorant, and 100 ppm hydroquinone, and first react in a low vacuum environment of 265°C and 8 kPa for 1 hour to remove excess ethylene glycol; then react in a high vacuum environment of 275°C and 30 Pa for 1.5 hours; after the polycondensation reaction is completed, break the vacuum with nitrogen, pressurize the material, cut into pellets underwater, and dry to obtain polyester chips.

[0043] (4) Wire forming: The polyester chips were dried at 70° C. until the water content was less than 500 ppm, and then cooled to room temperature; 2500 ppm calcium stearate and 1000 ppm 1-hydroxycyclohexyl ketone were added to the dried polyester chips, mixed in a high-speed mixer for 20 min, and then added to a single-screw extruder for extrusion, wherein the temperature of each heating zone of the single-screw extruder was set to: 185° C. for zone 1, 215° C. for zone 2, 225° C. for zone 3, 225° C. for zone 4, and 225° C. for zone 5, and the circulating cooling water temperature was 25° C., to obtain a PETG wire with a diameter of 1.75 mm±0.05 mm.

[0044] Example 3 (1) Alcoholysis of waste PETG: 1500 g of the waste PETG nozzle material powder after crushing, washing and drying was weighed and added into a 5L stainless steel reactor, and then 500 ppm of zinc acetate dihydrate, 1500 g of ethylene glycol (accounting for 100% of the mass of the waste PETG nozzle material powder), and 150 g of CHDM (accounting for 10% of the mass of the waste PETG nozzle material powder) were added into the reactor, and nitrogen was introduced and heated. The reaction was carried out at 240° C. under a nitrogen pressure of 100 kPa for 2 h to obtain an alcoholysis solution.

[0045] (2) Esterification / ester exchange reaction: After the pressure is released, 375 g of maleic anhydride (accounting for 25% of the mass of the waste PETG nozzle material powder) is added to the reactor and stirred evenly. The esterification / ester exchange reaction occurs at 240°C and 150 kPa nitrogen pressure using a three-way nitrogen release. Part of the ethylene glycol is distilled out of the esterification tower. The reaction time is 4 h.

[0046] (3) Polycondensation reaction: Add titanium glycol (Ti added in an amount of 20 ppm), triphenyl phosphate (P added in an amount of 15 ppm), 800 ppm antioxidant 1010, 400 ppm antioxidant 168, 5 ppm red and blue colorant, and 100 ppm hydroquinone, and first react in a low vacuum environment of 265°C and 8 kPa for 1 hour to remove excess ethylene glycol; then react in a high vacuum environment of 275°C and 30 Pa for 1.5 hours; after the polycondensation reaction is completed, break the vacuum with nitrogen, pressurize the material, cut into pellets underwater, and dry to obtain polyester chips.

[0047] (4) Wire forming: The polyester chips were dried at 70°C until the water content was less than 500 ppm, and then cooled to room temperature; 1500 ppm calcium stearate and 1000 ppm benzophenone were added to the dried polyester chips, mixed in a high-speed mixer for 20 min, and then added to a single-screw extruder for extrusion, wherein the temperature of each heating zone of the single-screw extruder was set to: 185°C for zone 1, 215°C for zone 2, 225°C for zone 3, 225°C for zone 4, and 225°C for zone 5, and the circulating cooling water temperature was 25°C, to obtain a PETG wire with a diameter of 1.75 mm±0.05 mm.

[0048] Example 4 (1) Alcoholysis of waste PETG: 1500 g of the waste PETG nozzle material powder after crushing, washing and drying was weighed and added into a 5L stainless steel reactor, and then 500 ppm of zinc acetate dihydrate, 1500 g of ethylene glycol (accounting for 100% of the mass of the waste PETG nozzle material powder), and 150 g of CHDM (accounting for 10% of the mass of the waste PETG nozzle material powder) were added into the reactor, and nitrogen was introduced and heated. The reaction was carried out at 240° C. under a nitrogen pressure of 100 kPa for 2 h to obtain an alcoholysis solution.

[0049] (2) Esterification / ester exchange reaction: After the pressure is released, 225 g of maleic acid (accounting for 15% of the mass of the waste PETG nozzle material powder) is added to the reactor and stirred evenly. The esterification / ester exchange reaction occurs at 240°C and 150 kPa nitrogen pressure using a three-way nitrogen release. Part of the ethylene glycol is distilled out of the esterification tower. The reaction time is 4 h.

[0050] (3) Polycondensation reaction: Add titanium glycol (Ti added in an amount of 20 ppm), triphenyl phosphate (P added in an amount of 15 ppm), 800 ppm antioxidant 1010, 400 ppm antioxidant 168, 5 ppm red and blue colorant, and 100 ppm hydroquinone, and first react in a low vacuum environment of 265°C and 8 kPa for 1 hour to remove excess ethylene glycol; then react in a high vacuum environment of 275°C and 30 Pa for 1.5 hours; after the polycondensation reaction is completed, break the vacuum with nitrogen, pressurize the material, cut into pellets underwater, and dry to obtain polyester chips.

[0051] (4) Wire forming: The polyester chips were dried at 70°C until the water content was less than 500 ppm, and then cooled to room temperature; 1500 ppm calcium stearate and 1000 ppm benzophenone were added to the dried polyester chips, mixed in a high-speed mixer for 20 min, and then added to a single-screw extruder for extrusion, wherein the temperature of each heating zone of the single-screw extruder was set to: 185°C for zone 1, 215°C for zone 2, 225°C for zone 3, 225°C for zone 4, and 225°C for zone 5, and the circulating cooling water temperature was 25°C, to obtain a PETG wire with a diameter of 1.75 mm±0.05 mm.

[0052] Example 5 (1) Alcoholysis of waste PETG: 1500 g of the waste PETG nozzle material powder after crushing, washing and drying was weighed and added into a 5L stainless steel reactor, and then 500 ppm of zinc acetate dihydrate, 1500 g of ethylene glycol (accounting for 100% of the mass of the waste PETG nozzle material powder), and 225 g of CHDM (accounting for 15% of the mass of the waste PETG nozzle material powder) were added into the reactor, and nitrogen was introduced and heated. The reaction was carried out at 240° C. under a nitrogen pressure of 100 kPa for 2 h to obtain an alcoholysis solution.

[0053] (2) Esterification / ester exchange reaction: After depressurization, 370 g of maleic acid (accounting for 25% of the mass of the waste PETG nozzle material powder) was added to the reactor and stirred evenly. The esterification / ester exchange reaction occurred at 240°C and 150 kPa nitrogen pressure using a three-way nitrogen release. Part of the ethylene glycol was distilled out of the esterification tower. The reaction time was 4 h.

[0054] (3) Polycondensation reaction: Add titanium glycol (Ti added in an amount of 20 ppm), triphenyl phosphate (P added in an amount of 15 ppm), 800 ppm antioxidant 1010, 400 ppm antioxidant 168, 5 ppm red and blue colorant, and 100 ppm hydroquinone, and first react in a low vacuum environment of 265°C and 8 kPa for 1 hour to remove excess ethylene glycol; then react in a high vacuum environment of 275°C and 30 Pa for 1.5 hours; after the polycondensation reaction is completed, break the vacuum with nitrogen, pressurize the material, cut into pellets underwater, and dry to obtain polyester chips.

[0055] (4) Wire forming: The polyester chips were dried at 70°C until the water content was less than 500 ppm, and then cooled to room temperature; 1500 ppm calcium stearate and 1000 ppm benzophenone were added to the dried polyester chips, mixed in a high-speed mixer for 20 min, and then added to a single-screw extruder for extrusion, wherein the temperature of each heating zone of the single-screw extruder was set to: 185°C for zone 1, 215°C for zone 2, 225°C for zone 3, 225°C for zone 4, and 225°C for zone 5, and the circulating cooling water temperature was 25°C, to obtain a PETG wire with a diameter of 1.75 mm±0.05 mm.

[0056] Comparative Example 1 The method of this comparative example is substantially the same as that of Example 1, except that CHDM is not added.

[0057] (1) Alcoholysis of waste PETG: 1500 g of the waste PETG nozzle material powder after crushing, washing and drying was weighed and added into a 5L stainless steel reactor, and then 500 ppm of zinc acetate dihydrate and 1500 g of ethylene glycol (accounting for 100% of the mass of the waste PETG nozzle material powder) were added into the reactor, and nitrogen was introduced and heated. The reaction was carried out at 240° C. under a nitrogen pressure of 100 kPa for 2 h to obtain an alcoholysis solution.

[0058] (2) Esterification / ester exchange reaction: After depressurization, 375 g of maleic acid (accounting for 25% of the mass of the waste PETG nozzle material powder) was added to the reactor and stirred evenly. The esterification / ester exchange reaction occurred at 240°C and 150 kPa nitrogen pressure using a three-way nitrogen release. Part of the ethylene glycol was distilled out of the esterification tower. The reaction time was 4 h.

[0059] (3) Polycondensation reaction: Add titanium glycol (Ti added in an amount of 20 ppm), triphenyl phosphate (P added in an amount of 15 ppm), 800 ppm antioxidant 1010, 400 ppm antioxidant 168, 5 ppm red and blue colorant, and 100 ppm hydroquinone, and first react in a low vacuum environment of 265°C and 8 kPa for 1 hour to remove excess ethylene glycol; then react in a high vacuum environment of 275°C and 30 Pa for 1.5 hours; after the polycondensation reaction is completed, break the vacuum with nitrogen, pressurize the material, cut into pellets underwater, and dry to obtain polyester chips.

[0060] (4) Wire forming: The polyester chips were dried at 70°C until the water content was less than 500 ppm, and then cooled to room temperature; 1500 ppm calcium stearate and 1000 ppm benzophenone were added to the dried polyester chips, mixed in a high-speed mixer for 20 min, and then added to a single-screw extruder for extrusion, wherein the temperature of each heating zone of the single-screw extruder was set to: 185°C for zone 1, 215°C for zone 2, 225°C for zone 3, 225°C for zone 4, and 225°C for zone 5, and the circulating cooling water temperature was 25°C, to obtain a PETG wire with a diameter of 1.75 mm±0.05 mm.

[0061] Comparative Example 2 The method of this comparative example is basically the same as that of Example 1, except that too much maleic acid is added.

[0062] (1) Alcoholysis of waste PETG: 1500 g of the waste PETG nozzle material powder after crushing, washing and drying was weighed and added into a 5L stainless steel reactor, and then 500 ppm of zinc acetate dihydrate, 1500 g of ethylene glycol (accounting for 100% of the mass of the waste PETG nozzle material powder), and 150 g of CHDM (accounting for 10% of the mass of the waste PETG nozzle material powder) were added into the reactor, and nitrogen was introduced and heated. The reaction was carried out at 240° C. under a nitrogen pressure of 100 kPa for 2 h to obtain an alcoholysis solution.

[0063] (2) Esterification / transesterification reaction: After pressure relief, 525 g of maleic acid (35% of the mass of the waste PETG regrind powder) was added into the reaction kettle, stirred evenly, and esterification / transesterification reaction occurred under the nitrogen pressure condition of 240 °C and 150 kPa by using a nitrogen three-way valve for three releases. Part of ethylene glycol was fractionated out by the esterification tower, and the reaction time was 4 h.

[0064] (3) Polycondensation reaction: Ethylene glycol titanate (Ti addition amount is 20 ppm), triphenyl phosphate (P addition amount is 15 ppm), 800 ppm antioxidant 1010, 400 ppm antioxidant 168, 5 ppm red and blue toner, and 100 ppm hydroquinone were added. First, the reaction was carried out under a low vacuum environment of 265 °C and 8 kPa for 1 h to remove excess ethylene glycol; then the reaction was carried out under a high vacuum environment of 275 °C and 30 Pa for 1.5 h. After the polycondensation reaction was completed, the vacuum was broken with nitrogen, pressurized for discharging, underwater pelletized and dried to obtain polyester chips.

[0065] (4) Wire forming: The polyester chips were dried at 70 °C until the water content was less than 500 ppm and cooled to room temperature; 1500 ppm of calcium stearate and 1000 ppm of benzophenone were added to the dried polyester chips, mixed in a high-speed mixer for 20 min, and then extruded into a single-screw extruder. The temperature settings of each heating zone of the single-screw extruder were: zone 1 at 185 °C, zone 2 at 215 °C, zone 3 at 225 °C, zone 4 at 225 °C, zone 5 at 225 °C, and the circulating cooling water temperature was 25 °C to obtain PETG wire with a diameter of 1.75 mm ± 0.05 mm.

[0066] Comparative Example 3 The method of this comparative example was basically the same as that of Example 1, except that no ultraviolet initiator was added in the wire forming stage.

[0067] (1) Alcoholysis of waste PETG: 1500 g of the waste PETG regrind powder after being crushed, washed and dried was added into a 5 L stainless steel reaction kettle, and then 500 ppm of zinc acetate dihydrate, 1500 g of ethylene glycol (100% of the mass of the waste PETG regrind powder), and 150 g of CHDM (10% of the mass of the waste PETG regrind powder) were added into the reaction kettle. Nitrogen was introduced and heated, and the reaction was carried out at 240 °C under the nitrogen pressure condition of 100 kPa for 2 h to obtain an alcoholysis solution.

[0068] (2) Esterification / transesterification reaction: After pressure relief, 375 g of maleic acid (25% of the mass of the waste PETG regrind powder) was added into the reaction kettle, stirred evenly, and esterification / transesterification reaction occurred under the nitrogen pressure condition of 240 °C and 150 kPa by using a nitrogen three-way valve for three releases. Part of ethylene glycol was fractionated out by the esterification tower, and the reaction time was 4 h.

[0069] (3) Polycondensation reaction: Add titanium glycol (Ti added in an amount of 20 ppm), triphenyl phosphate (P added in an amount of 15 ppm), 800 ppm antioxidant 1010, 400 ppm antioxidant 168, 5 ppm red and blue colorant, and 100 ppm hydroquinone, and first react in a low vacuum environment of 265°C and 8 kPa for 1 hour to remove excess ethylene glycol; then react in a high vacuum environment of 275°C and 30 Pa for 1.5 hours; after the polycondensation reaction is completed, break the vacuum with nitrogen, pressurize the material, cut into pellets underwater, and dry to obtain polyester chips.

[0070] (4) Wire forming: The polyester chips were dried at 70°C until the water content was less than 500 ppm, and then cooled to room temperature; 1500 ppm calcium stearate was added to the dried polyester chips, mixed in a high-speed mixer for 20 min, and then added to a single-screw extruder for extrusion, wherein the temperature of each heating zone of the single-screw extruder was set to: 185°C for zone 1, 215°C for zone 2, 225°C for zone 3, 225°C for zone 4, and 225°C for zone 5, and the circulating cooling water temperature was 25°C, to obtain a PETG wire with a diameter of 1.75 mm±0.05 mm.

[0071] Comparative Example 4 The method of this comparative example is basically the same as that of Example 1, except that no lubricant is added during the wire forming stage.

[0072] (1) Alcoholysis of waste PETG: 1500 g of the waste PETG nozzle material powder after crushing, washing and drying was weighed and added into a 5L stainless steel reactor, and then 500 ppm of zinc acetate dihydrate, 1500 g of ethylene glycol (accounting for 100% of the mass of the waste PETG nozzle material powder), and 150 g of CHDM (accounting for 10% of the mass of the waste PETG nozzle material powder) were added into the reactor, and nitrogen was introduced and heated. The reaction was carried out at 240° C. under a nitrogen pressure of 100 kPa for 2 h to obtain an alcoholysis solution.

[0073] (2) Esterification / ester exchange reaction: After depressurization, 375 g of maleic acid (accounting for 25% of the mass of the waste PETG nozzle material powder) was added to the reactor and stirred evenly. The esterification / ester exchange reaction occurred at 240°C and 150 kPa nitrogen pressure using a three-way nitrogen release. Part of the ethylene glycol was distilled out of the esterification tower. The reaction time was 4 h.

[0074] (3) Polycondensation reaction: Add titanium glycolate (the addition amount of Ti is 20 ppm), triphenyl phosphate (the addition amount of P is 15 ppm), 800 ppm antioxidant 1010, 400 ppm antioxidant 168, 5 ppm red and blue toner, and 100 ppm hydroquinone. First, react for 1 h under a low vacuum environment of 265 °C and 8 kPa to remove excess ethylene glycol; then react for 1.5 h under a high vacuum environment of 275 °C and 30 Pa. After the polycondensation reaction is completed, break the vacuum with nitrogen, pressurize and discharge the material, cut into pellets underwater, and dry to obtain polyester chips.

[0075] (4) Wire forming: Dry the polyester chips at 70 °C until the water content is less than 500 ppm, and cool to room temperature; add 1000 ppm benzophenone to the dried polyester chips, mix in a high-speed mixer for 20 min, and then extrude into a single-screw extruder. The temperature settings of each heating zone of the single-screw extruder are: zone 1 at 185 °C, zone 2 at 215 °C, zone 3 at 225 °C, zone 4 at 225 °C, zone 5 at 225 °C, and the circulating cooling water temperature is 25 °C to obtain PETG wire with a diameter of 1.75 mm ± 0.05 mm.

[0076] Comparative Example 5 The method of this comparative example is the same as that of Example 1, except that ultraviolet light irradiation is not performed in the 3D printing stage.

[0077] Print and conduct relevant tests on the PETG wire in Example 1 using a PDM type 3D printer. Printing conditions: The printing nozzle temperature is controlled at 250 °C, the heated bed temperature is controlled at 80 °C, and the printing speed is 40 mm / s.

[0078] Comparative Example 6 The method of this comparative example is the same as that of Example 1, except that ultraviolet light irradiation is not performed at the printing nozzle in the 3D printing stage.

[0079] Print and conduct relevant tests on the PETG wire in Example 1 using a PDM type 3D printer. Printing conditions: The printing nozzle temperature is controlled at 250 °C, the heated bed temperature is controlled at 80 °C, the printing speed is 40 mm / s, and the printed part after printing is further irradiated in an ultraviolet light irradiation device (ultraviolet lamp power 2 kw, power density 120 W / cm 2 , main wavelength 365 nm) for 2 min.

[0080] Print and conduct relevant tests on the wires of Examples 1-5 and Comparative Examples 1-4 using a PDM type 3D printer. Printing conditions: The printing nozzle temperature is controlled at 250 °C, the heated bed temperature is controlled at 80 °C, the printing speed is 40 mm / s, and an ultraviolet light source (power density 100 W / cm 2, with a main wavelength of 365 nm), and the printed piece after printing is irradiated in an ultraviolet light irradiation device (ultraviolet lamp power 2 kw, power density 120 W / cm 2 for 2 min at a main wavelength of 365 nm).

[0081] The mechanical properties of the test specimens were tested according to GB / T 1040.1-2018. The specimens were 1A dumbbell-shaped specimens (thickness 4 mm, gauge length 50 mm, initial distance between clamps 115 mm).

[0082] The impact properties of the test specimens were tested according to ISO 179. The specimens were notched specimens (type A notch) with dimensions of 80 mm * 10 mm * 4 mm.

[0083] The transparency of the printed pieces was tested according to GB / T 2410-2008. The specimens were circular discs with a radius of 30 mm and a thickness of 1 mm.

[0084] A 10 mm * 10 mm * 2 mm grid specimen was printed, and the accuracy of the microscopic printing process was observed by SEM.

[0085] The printer was used to print 1A dumbbell-shaped specimens, and the surface pit conditions were observed. The test results are shown in Table 1.

[0086] Table 1 From the comparison of the data parameters of the examples and comparative examples in Table 1, it can be seen that: (1) Comparison between Examples 1-5 and Comparative Examples 1-6: The specimens cured by ultraviolet light all showed improved tensile properties and impact resistance, and well achieved that the material did not stick to the nozzle, the printed pieces did not warp, and the surface was smooth.

[0087] (2) Comparison between Examples 1 and 5 and Comparative Example 1: Only ethylene glycol was added during the alcoholysis process of waste PETG, and CHDM was not added. Since unsaturated dibasic acids / dianhydrides were also added for copolymerization during the subsequent polymerization process, the proportion of CHDM in the resulting recycled PETG would be reduced, which would affect the light transmittance and toughness of the recycled PETG. However, if the addition amount of CHDM is too much, the proportion of CHDM in the resulting recycled PETG will be too high, making its chemical structure closer to that of PCTG, which will also affect the transparency.

[0088] (3) Comparison between Examples 1, 4 and Comparative Example 2: By introducing unsaturated monomers into the PETG system, ultraviolet curing can be achieved during the 3D printing process, reducing the problems of warping, shrinkage, and adhesion of 3D printed parts. However, if there is too much unsaturated dibasic acid / dianhydride, the softening temperature of the recycled PETG will decrease, the tensile strength will decrease, the mechanical strength of the material will decline, and the printing accuracy will also be affected.

[0089] (4) Comparison between Example 1 and Comparative Examples 3 and 5: In the ultraviolet initiator-free system and the ultraviolet treatment-free system, there are fewer crosslinking sites, the mechanical properties of the specimens decrease significantly, and the printed parts are prone to deformation and have low printing accuracy.

[0090] (5) Comparison between Example 1 and Comparative Example 4: In the wire forming stage, the addition of lubricant is lacking, the melt fluidity at the nozzle is slightly poor, and it is easy to stick to the nozzle, resulting in a few pits on the surface of the specimen and low printing accuracy.

[0091] (4) Comparison between Example 1 and Comparative Example 6: There is no ultraviolet light irradiation at the nozzle, the material is easy to stick to the nozzle, resulting in a few pits on the surface of the specimen and low printing accuracy.

[0092] By using the method of the present invention, unsaturated monomers are introduced into the PETG system. By adding a polymerization inhibitor to protect the unsaturated bonds during the polycondensation stage and adding an initiator and a lubricant during the wire forming stage, ultraviolet curing can be achieved during the 3D printing process, solving the technical problems such as warping and shrinkage of 3D printed parts made of PETG, and realizing the preparation of photocurable 3D printing PETG wire from PETG regrind.

[0093] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A method for preparing a photocurable 3D printing material from waste PETG, characterized in that, It includes the following steps: (1) Add an alcoholysis agent, ethylene glycol, and 1,4-cyclohexanedimethanol to the waste PETG powder, introduce nitrogen, and carry out an alcoholysis reaction to obtain an oligomer; (2) Add maleic acid or maleic anhydride to the oligomer to carry out an esterification / transesterification reaction; then add a polycondensation catalyst, a polymerization inhibitor, and an auxiliary agent to carry out a polycondensation reaction; after the reaction is completed, pelletize and dry to obtain polyester chips; (3) Mix the polyester chips with a lubricant and a UV initiator, and then melt and extrude to obtain a photocurable 3D printing material.

2. The method for preparing a photocurable 3D printing material from waste PETG according to claim 1, wherein In step (1), the mass ratio of the ethylene glycol to the waste PETG powder is 1-3:1; the mass ratio of the 1,4-cyclohexanedimethanol to the waste PETG powder is 10-15:

100.

3. The method for preparing a photocurable 3D printing material from waste PETG according to claim 1, wherein, In step (1), the alcoholysis agent is one or more of titanium glycolate, cobalt acetate, cobalt acetate tetrahydrate, zinc acetate, and zinc acetate dihydrate; the addition amount of the alcoholysis agent is 200-5000 ppm of the mass of the waste PETG powder.

4. The method for preparing a photocurable 3D printing material from waste PETG according to claim 1 or 2 or 3, characterized in that, In step (1), the temperature of the alcoholysis reaction is 170-280 °C, the nitrogen pressure condition is 50-150 kPa, and the reaction time is 1-8 h.

5. The method for preparing a photocurable 3D printing material from waste PETG according to claim 1, characterized in that, In step (2), the mass ratio of the maleic acid or maleic anhydride to the waste PETG powder is 5-25:100; the temperature of the esterification / transesterification reaction is 200-240 °C, the nitrogen pressure condition is 50-150 kPa, and the reaction time is 1-6 h.

6. The method for preparing a photocurable 3D printing material from waste PETG according to claim 1, wherein In step (2), the addition amount of titanium or antimony element in the polycondensation catalyst is 4-200 ppm of the mass of the waste PETG powder; the addition amount of the polymerization inhibitor is 50-150 ppm of the mass of the waste PETG powder; the auxiliary agent includes a stabilizer, an antioxidant, and a color toner.

7. The method for preparing a photocurable 3D printing material from waste PETG according to claim 1 or 5 or 6, characterized in that, In step (2), the polycondensation reaction is as follows: first react in a low vacuum environment of 240-260 °C and 1-10 kPa for 1 h; then react in a high vacuum environment of 260-290 °C and 10-100 Pa for 1-4 h.

8. The method for preparing a photocurable 3D printing material from waste PETG according to claim 1, wherein In step (3), the addition amount of the lubricant is 100-3000 ppm of the mass of the waste PETG powder; the addition amount of the UV initiator is 500-3000 ppm of the mass of the waste PETG powder.

9. The method for preparing a photocurable 3D printing material from waste PETG according to claim 1 or 8, characterized in that In step (3), the temperature of the melt extrusion is 180-230 °C.

10. Use of a photocurable 3D printing material obtained by the method according to any one of claims 1-9 in 3D printing, characterized in that, Use the photocurable 3D printing material for 3D printing, and irradiate with ultraviolet light at the printing nozzle and on the printed part after printing is completed.

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