Method for preparing chain-extended polyurethane adhesive by using waste PET (Polyethylene Terephthalate) degradation product

Abstract

The invention discloses a method for preparing a chain extension polyurethane adhesive by using a waste PET degradation product, and the method specifically comprises the following steps: dissolving a pretreated waste PET plastic sheet in a mixed solution of 1, 4-butynediol and 1, 4-cyclohexanediol, carrying out alcoholysis reaction, adding zinc oxide, and continuing the reaction to obtain a waste PET alcoholysis solution; the preparation method comprises the following steps: carrying out a reaction on PPG and IPDI to prepare an NCO-terminated polyurethane prepolymer; and adding the waste PET alcoholysis solution serving as a chain extender into the polyurethane prepolymer to generate the polyurethane adhesive. The polyurethane adhesive prepared by the invention is excellent in performance, and has the advantages that rigid benzene rings and strong polar ester groups in a PET molecular chain are successfully introduced into a polyurethane system, so that the cohesive force and interface adhesive force of a product are remarkably enhanced, and the polyurethane adhesive is endowed with excellent bonding strength; meanwhile, the crosslinking density and the microphase separation degree are improved, and excellent mechanical strength and heat resistance are brought.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of adhesive preparation, and particularly relates to a method for preparing a chain-extended polyurethane adhesive by using waste PET degradation products. BACKGROUND

[0002] Polyurethane (PU) is one of the most widely used polymers, which has been widely used in the fields of construction, machinery, furniture, clothing, textiles, packaging and biological medicine. Polyurethane is a block polymer made of long-chain and short-chain raw materials. Long-chain polyols form soft segments, while hard segments are composed of short-chain polyisocyanate.

[0003] Polyethylene terephthalate (PET) is a semi-crystalline thermoplastic polyester with high strength, high transparency and safety performance, which is usually used for storing products such as plastic bottles. However, PET is a non-degradable plastic under normal circumstances, and the durability of this material will cause serious environmental pollution. In this case, it is very important to reduce the number of plastic garbage and recycle PET from low-cost sources to produce valuable materials. Fermentation is a reaction that converts a heterogeneous system into a single phase. The alcoholysis reaction of waste PET bottles degrades into oligomers, and carboxyl and hydroxyl end groups are used as building blocks to produce new polyesters. Therefore, it is of great significance to extract value-added monomers from waste polymers as raw materials to prepare polyurethane materials. SUMMARY

[0004] The purpose of the present application is to provide a method for preparing a chain-extended polyurethane adhesive by using waste PET degradation products, which has good adhesion.

[0005] The technical solution adopted by the present application is a method for preparing a chain-extended polyurethane adhesive by using waste PET degradation products, which is implemented according to the following steps: Step 1, preparing a waste PET alcoholysis solution; Step 2, preparing an NCO-terminated polyurethane prepolymer by reacting PPG and IPDI; Step 3, adding the waste PET alcoholysis solution prepared in step 1 as a chain extender to the polyurethane prepolymer to generate a polyurethane adhesive.

[0006] The present application is also characterized in that, In step 1, specifically: Step 1.1, pretreating the waste PET plastic: The waste PET plastic is cut into pieces, the PET plastic pieces are soaked in an HCl solution, stirred for 10-12 min, and then filtered out, and washed with deionized water; then the PET plastic pieces are soaked in a NaOH solution, stirred for 10-12 min, filtered out, and washed with deionized water again; finally, the pieces are dried in a blast drying oven at 50-55°C to obtain pretreated waste PET plastic pieces. In step 1.2, the pretreated waste PET plastic pieces are dissolved in a mixture of 1,4-butynediol and 1,4-cyclohexanediol, and an alcoholysis reaction is carried out under oil bath stirring, and the reaction is continued after the addition of zinc oxide, and then frozen recrystallization, boiling water extraction, and hot filtration of the residue are carried out to obtain a waste PET alcoholysis solution.

[0007] In step 1.2, the mass ratio of the waste PET plastic pieces, 1,4-butynediol, and 1,4-cyclohexanediol is 1-1.1:1:1, and the mass of zinc oxide is 1-1.5% of the mass of the waste PET plastic pieces.

[0008] In step 1.2, the reaction process is as follows: first, adjust the oil bath temperature to 160-165°C, and the stirring speed to 250-255 r / min, and react for 1-1.5 h; then, after the addition of zinc oxide, adjust the oil bath temperature to 180-185°C, and the stirring speed to 400-405 r / min, and react for 3.5-4 h; then, keep the oil bath temperature unchanged, and adjust the stirring speed to 500-505 r / min, and continue to react for 35-40 min.

[0009] In step 1.2, the frozen recrystallization temperature is -10~0°C, and the time is 24-25 h.

[0010] In step 2, the specific process is as follows: The PPG is placed in a vacuum drying oven, then IPDI is added, and the mixture is placed in a water bath for condensation reflux stirring reaction, the reaction temperature is 80-85°C, the reaction time is 1-1.5 h, and the stirring speed is 250-255 r / min; then, the catalyst dibutyltin dilaurate is added, and the reaction is continued for 2-2.5 h to generate a polyurethane prepolymer.

[0011] The molar ratio of the isocyanate group of IPDI to the hydroxyl group of PPG is 2 / 3-2 / 5, and the amount of dibutyltin dilaurate added is 0.5-1% of the mass of PPG.

[0012] In step 3, the specific process is as follows: The waste PET alcoholysis solution and the polyurethane prepolymer are mixed and subjected to chain extension stirring reaction, the reaction temperature is 80-85°C, the reaction time is 2-2.5 h, the stirring speed is 300-305 r / min, and the mixture is dried at 60°C for 24 h to obtain a polyurethane adhesive.

[0013] The mass ratio of the waste PET alcoholysis solution to the polyurethane prepolymer is 0.5-1:20-25.

[0014] The method of the application realizes high-value utilization of waste by preparing the polyurethane adhesive using the waste PET alcoholysis product. The prepared polyurethane adhesive has excellent performance, and the advantage is that the rigid benzene ring and strong polar ester group in the PET molecular chain are successfully introduced into the polyurethane system. This significantly enhances the internal cohesion and interfacial adhesion of the product, giving it excellent bonding strength; at the same time, the crosslinking density and microphase separation degree are improved, bringing outstanding mechanical strength and heat resistance. At the same time, the method is not only low in cost and green in environment, but also creates a high-quality adhesive with better comprehensive performance than traditional products. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is the Fourier infrared test (FTIR) diagram of the PET alcoholysis product and the polyurethane adhesive of the application; Figure 2 is a viscosity change curve graph of the polyurethane adhesive of the application for dynamic rheological property testing with temperature change; Figure 3 is a curve graph of storage modulus and loss modulus with strain change of the polyurethane adhesive of the application for dynamic rheological property testing; Figure 4 is a thermogravimetric (TG) and TG first derivative (DTG) curve graph of the polyurethane adhesive of the application; Figure 5 is a differential scanning calorimetry (DSC) curve graph of the polyurethane adhesive of the application; Figure 6 is a lap shear strength graph of the polyurethane adhesive of the application on different substrates. DETAILED DESCRIPTION

[0016] The application will be described in detail below in combination with the drawings and specific embodiments.

[0017] The method for preparing the chain-extended polyurethane adhesive using the waste PET degradation product of the application is implemented according to the following steps: Step 1, preparing a waste PET alcoholysis solution; specifically: Step 1.1, pretreating the waste PET plastic, specifically: The waste PET plastic is cut into 1cm*1cm pieces, the PET plastic pieces are soaked in an HCl solution, stirred for 10-12min, and then filtered out, and washed with deionized water for 3-4 times; then the PET plastic pieces are soaked in a NaOH solution, stirred for 10-12min, and then filtered out, and washed with deionized water for 3-4 times; finally, the waste PET plastic pieces are dried in a blast drying oven at 50-55℃, to obtain pretreated waste PET plastic pieces; The concentration of the HCl solution is 5-5.1mol / L; the concentration of the NaOH solution is 5-5.1mol / L; Step 1.2, the pretreated waste PET plastic pieces are dissolved in a mixture of 1,4-butynediol and 1,4-cyclohexanediol, and alcoholysis reaction is carried out under oil bath stirring, and then zinc oxide is added to continue the alcoholysis reaction, and then frozen recrystallization, boiling water extraction, and hot filtration of the residue are carried out, to obtain waste PET alcoholysis solution (GOP); The mass ratio of the waste PET plastic pieces, 1,4-butynediol and 1,4-cyclohexanediol is 1-1.1:1:1; The oil bath temperature is 160-165℃, and the stirring time is 1-1.5h; the stirring speed is 250-255r / min; The mass of zinc oxide is 1-1.5% of the mass of the waste PET plastic pieces; After adding zinc oxide, the oil bath temperature is adjusted to 180-185℃, the stirring speed is adjusted to 400-405r / min, and the reaction time is 3.5-4h; then the oil bath temperature is kept unchanged, and the stirring speed is adjusted to 500-505r / min, and the reaction is continued for 35-40min.

[0018] The frozen recrystallization temperature is -10~0℃, and the time is 24-25h; The boiling water extraction process is: deionized water is added and heated to 100℃, and the undegraded residue is hot filtered out, and the process is repeated three times; the filtrate is collected, and then rotary evaporation is carried out at 40-45℃ for 30-35min, the rotary speed is 65rpm, and the vacuum degree is 160hpa.

[0019] Step 2, NCO-terminated polyurethane prepolymer is prepared by reacting polypropylene glycol 2000 (PPG) and isophorone diisocyanate (IPDI); The PPG is vacuum dried in a vacuum drying oven at 110℃ for 2h, then IPDI is added, and the condensation reflux stirring reaction is carried out in a water bath, then the catalyst dibutyltin dilaurate is added, and the reaction is continued for 2-2.5h, to obtain polyurethane prepolymer generated by PPG and IPDI; The index of isocyanate in the preparation process of the polyurethane prepolymer is 1.5-2.5, that is, the molar ratio of isocyanate groups (NCO) of IPDI to hydroxyl groups (OH) of PPG is 2 / 3-2 / 5; The stirring reaction temperature is 80-85 DEG C, the stirring reaction time is 1-1.5 h, and the stirring speed is 250-255 r / min; The adding amount of dibutyltin dilaurate is 0.5-1% of the mass of PPG; Step 3, the waste PET alcoholysis solution prepared in step 1 is added into the polyurethane prepolymer as a chain extender to generate a polyurethane adhesive (PU-GOP); specifically: The waste PET alcoholysis solution is mixed with the polyurethane prepolymer, chain extension stirring reaction is carried out, drying is carried out at 60 DEG C for 24 h, and a polyurethane adhesive is obtained; The mass ratio of the waste PET alcoholysis solution to the polyurethane prepolymer is 0.5-1:20-25; The reaction temperature is 80-85 DEG C, the reaction time is 2-2.5 h, and the stirring speed is 300-305 r / min.

[0020] The method of the application comprises two steps of alcoholysis reaction of waste PET bottles and polyurethane synthesis, the PET degradation product contains a large amount of hydroxyl groups, can replace the polyurethane chain extender component, completes the chain extension reaction of the polyurethane prepolymer, and the reaction product has good adhesion.

[0021] Example 1 The method for preparing the chain extension polyurethane adhesive by using the waste PET degradation product according to the application is implemented according to the following steps: Step 1, preparing a waste PET alcoholysis solution: The waste PET plastic is cut into 1cm*1cm fragments, the PET plastic fragments are soaked in a 5mol / L HCl solution, stirred for 10 min, and then the PET plastic fragments are filtered out and washed with deionized water for 3 times; then the PET plastic fragments are soaked in a 5mol / L NaOH solution, stirred for 10 min, filtered out, and washed with deionized water for 3 times; finally, the pretreated waste PET plastic fragments are placed in a blast drying oven and dried at 50 DEG C, to obtain the pretreated waste PET plastic fragments; Take 30.032 g of clean PET chips, 30.790 g of 1,4-butynediol and 30.246 g of 1,4-cyclohexanediol, and put them into a 500 ml round-bottom three-neck flask, one of which is equipped with a stirring head, one is connected with a condensation reflux device, and the third is used as a feeding port, and is placed in a 160℃ oil bath, and is mechanically stirred at a speed of 250 r / min for 1 h. During the reaction, the three ports are sealed with sealing paper to prevent water vapor from entering the reaction system. Then add 3 drops of zinc oxide, adjust the oil bath temperature to 180℃, and the stirring speed to 400 r / min, and react for 3.5 h. Then adjust the stirring speed to 500 r / min, and react for 35 min after stopping stirring. Take the three-neck flask out of the oil bath, and let it stand at room temperature for 20 min. Collect the sample in a flask, and freeze recrystallize in a refrigerator at -10℃ for 24 h. Then add 5 ml of deionized water, heat to 100℃ for boiling water extraction, and filter the undegraded residue, repeat three times; collect the filtrate, and then perform rotary evaporation for 30 min at a temperature of 40℃ and a rotation speed of 65 rpm, and a vacuum degree of 160 hpa. Finally, collect the PET degradation liquid GOP.

[0022] Step 2, pretreatment of PPG 2000: take 20.101 g of PPG 2000 and put it into a 250 ml three-neck round-bottom flask, and dry it in a vacuum drying box at 110℃ for 2 h to remove water before use. Then take it out and plug the bottle mouth with a bottle plug, and then add 5.612 g of IPDI (isocyanate index R = 2.5), one of which is equipped with a stirring head, one is connected with a condensation reflux device, and the third is used as a feeding port, and is placed in an 80℃ oil bath, and is mechanically stirred at a speed of 250 r / min for 1 h. Then add 3 drops of dibutyltin dilaurate, and react for 2 h. Then the PPG and IPDI form a polyurethane prepolymer.

[0023] Step 3, take 0.4 ml of the extracted PET degradation liquid prepared in step 1 as a chain extender and add it to the polyurethane prepolymer reaction system, adjust the stirring speed to 300 r / min, and react for 2 h to perform chain extension reaction, and finally react in an oven at 60℃ for 24 h to generate polyurethane PU-GOP 2.5.

[0024] Example 2 The method for preparing a chain-extended polyurethane adhesive using waste PET degradation products according to the present application is implemented according to the following steps: Step 1, preparation of waste PET alcoholysis liquid; specifically: The waste PET plastic is cut into 1 cm*1 cm pieces, the PET plastic pieces are soaked in a 5.1 mol / L HCl solution, stirred for 12 min, then the PET plastic pieces are filtered out, washed with deionized water for 4 times; then the PET plastic pieces are soaked in a 5.1 mol / L NaOH solution, stirred for 12 min, the PET plastic pieces are filtered out, washed with deionized water for 4 times; finally, the pre-processed waste PET plastic pieces are dried in a forced air drying oven at 55°C to obtain the pre-processed waste PET plastic pieces; 30.0920g of clean PET pieces, 30.090g of 1,4-butynediol and 30.151g of 1,4-cyclohexanediol are weighed into a 500ml round-bottom three-necked flask, one of which is equipped with a stirring head, one is connected with a condensation reflux device, and the third is used as a feeding port, which is placed in an oil bath at 161°C, and mechanical stirring is carried out at a speed of 253r / min for 1.2h, and during the reaction, the three bottle openings are sealed with sealing paper to prevent water vapor from entering the reaction system; then 2-3 drops of zinc oxide are added, the oil bath temperature is adjusted to 180°C, and the stirring speed is 400r / min, and the reaction is carried out for 3.5h; then the stirring speed is adjusted to 502r / min, and after 37min of reaction, the stirring is stopped, the three-necked flask is taken out of the oil bath, and it is placed at room temperature for 21min. Collect the sample into a flask and place it in a refrigerator at-9°C for 24.5h. Then, 7ml of deionized water is added, and the temperature is heated to 100°C for boiling water extraction. Heat and filter the undegraded residue, repeat three times; collect the filtrate, then perform rotary evaporation for 33min at a temperature of 45°C and a rotation speed of 65rpm, and a vacuum degree of 160hpa. Finally, collect the PET degradation liquid GOP.

[0025] Step 2, pretreatment of PPG 2000: weigh PPG 2000=20.004g into a 250ml three-necked round-bottom flask, and before use, vacuum dry for 2.1h at 110°C in a vacuum drying oven to remove water. Then take out and plug the bottle opening with a bottle plug, then add 4.441g of IPDI (isocyanate index R=2), one of which is equipped with a stirring head, one is connected with a condensation reflux device, and the third is used as a feeding port, which is placed in an oil bath at 80°C, and mechanical stirring is carried out at a speed of 250r / min for 1h. Then add 2-3 drops of dibutyltin dilaurate, and react for 2h. Then the PPG and IPDI form a polyurethane prepolymer.

[0026] Step 3, 0.4ml of the extracted PET degradation liquid prepared in step 1 is added as a chain extender to the polyurethane prepolymer reaction system, the stirring speed is adjusted to 301r / min, and the chain extension reaction is carried out for 2.2h, and finally the oven is reacted at 60°C for 24h to generate polyurethane PU-GOP 2.

[0027] Example 3 The application utilizes waste PET degradation product to prepare a chain-extended polyurethane adhesive, and is specifically implemented according to the following steps: Step 1, preparing waste PET alcoholysis solution; specifically: The waste PET plastic is cut into 1cm*1cm fragments, the PET plastic fragments are soaked in a 5mol / L HCl solution, stirred for 12min, and then the PET plastic fragments are filtered out and washed with deionized water for 3 times; then the PET plastic fragments are soaked in a 5mol / L NaOH solution, stirred for 10min, and then the PET plastic fragments are filtered out and washed with deionized water for 3 times; finally, the pre-processed waste PET plastic fragments are dried in a blast drying oven at 50°C, and the pre-processed waste PET plastic fragments are obtained. 31.2690g of the cleaned PET fragments, 30.418g of 1,4-butynediol and 30.083g of 1,4-cyclohexanediol are weighed into a 500ml round-bottom three-neck flask, one of which is provided with a stirring head, one is connected with a condensation reflux device, and the third is used as a feeding port, which is placed in an oil bath at 160°C, and mechanical stirring is carried out at a speed of 250r / min for 1.1h, and during the reaction, the three bottle openings are sealed with sealing paper to prevent water vapor from entering the reaction system; then 2-3 drops of zinc oxide are added, the oil bath temperature is adjusted to 180°C, the stirring speed is 403r / min, and the reaction is carried out for 3.5h; then the stirring speed is adjusted to 502r / min, and after 37min of reaction, the stirring is stopped, the three-neck flask is taken out of the oil bath, and it is left to stand at room temperature for 21min. The sample is collected in a glass tube, and placed in a refrigerator at-10°C for 24.5h. Then, 6ml of deionized water is added, and the temperature is heated to 100°C for boiling water extraction. The undegraded residue is filtered hot and repeated three times. The filtrate is collected and then rotary evaporated for 35min at a temperature of 43°C, a rotary speed of 65rpm and a vacuum degree of 160hpa. Finally, the PET degradation solution GOP is collected.

[0028] Step 2, pretreatment of PPG 2000: 20.143g of PPG 2000 is weighed into a 250ml three-neck round-bottom flask, and before use, it is dried in a vacuum drying oven at 110°C for 2.2h to remove water. Then the bottle opening is plugged with a bottle plug, and 3.33g of IPDI (isocyanate index R=2) is added. One of the openings is provided with a stirring head, one is connected with a condensation reflux device, and the third is used as a feeding port, which is placed in an oil bath at 80°C, and mechanical stirring is carried out at a speed of 250r / min for 1.2h. Then 2-3 drops of dibutyltin dilaurate are added, and the reaction is carried out for 2.3h. Then the PPG and IPDI generate a polyurethane prepolymer.

[0029] Step 3, 0.4ml of the prepared extraction of PET degradation solution in step 1 is added as a chain extender to the polyurethane prepolymer reaction system, the rotating speed is adjusted to 302 r / min, the chain extension reaction is carried out for 2.1h, and finally the oven is reacted at 60℃ for 24h to generate polyurethane PU-GOP 1.5.

[0030] Example 4 The method for preparing a chain-extended polyurethane adhesive by using waste PET degradation products according to the present application is implemented according to the following steps: Step 1, preparation of waste PET alcoholysis solution; specifically: Step 1.1, pretreatment of waste PET plastic: The waste PET plastic is cut into 1cm*1cm pieces, the PET plastic pieces are soaked in 5mol / L HCl solution, stirred for 12min, and then filtered out, washed with deionized water for 3 times; then the PET plastic pieces are soaked in 5mol / L NaOH solution, stirred for 10min, filtered out, and washed with deionized water for 4 times; finally, put into a forced air drying oven and dried at 55℃ to obtain pretreated waste PET plastic pieces; Step 1.2, dissolve the pretreated waste PET plastic pieces in a mixture of 1,4-butynediol and 1,4-cyclohexanediol, stir under oil bath conditions for alcoholysis reaction, continue the alcoholysis reaction after adding catalyst zinc oxide, and then perform freeze recrystallization, boiling water extraction, and hot filtration to obtain waste PET alcoholysis solution (GOP); The mass ratio of waste PET plastic pieces, 1,4-butynediol and 1,4-cyclohexanediol is 1:1:1; The oil bath temperature is 165℃, the stirring time is 1.5h, and the stirring speed is 255r / min; The mass of zinc oxide is 1.5% of the mass of waste PET plastic pieces; After adding zinc oxide, the oil bath temperature is adjusted to 185℃, the stirring speed is adjusted to 400 r / min, and the reaction time is 3.5h; then the oil bath temperature is kept unchanged, the stirring speed is adjusted to 500 r / min, and the reaction is continued for 40min.

[0031] The freeze recrystallization temperature is-10℃, and the time is 24h; The boiling water extraction process is: deionized water is added to 100℃, the undegraded residue is hot filtered, and the process is repeated three times; the filtrate is collected, and then rotary evaporation is carried out at 45℃ for 35min, the rotary speed is 65 rpm, and the vacuum degree is 160 hpa.

[0032] Step 2, NCO-terminated polyurethane prepolymer is prepared by reacting polypropylene glycol 2000 (PPG) and isophorone diisocyanate (IPDI); PPG is vacuum dried in a vacuum drying oven at 110 DEG C for 2h, then IPDI is added, and the reaction is carried out under condensation reflux stirring in a water bath, then the catalyst dibutyltin dilaurate is added, and the reaction is continued for 2.5h, and the polyurethane prepolymer is prepared by using PPG and IPDI; The isocyanate index of the polyurethane prepolymer preparation process is 2.5, that is, the molar ratio of the isocyanate group (NCO) of IPDI to the hydroxyl group (OH) of PPG is 2 / 3; The stirring reaction temperature is 80 DEG C, the stirring reaction time is 1h, and the stirring speed is 255r / min; The amount of dibutyltin dilaurate added is 1% of the mass of PPG; Step 3, the waste PET alcoholysis solution prepared in step 1 is added to the polyurethane prepolymer as a chain extender to generate a polyurethane adhesive (PU-GOP); specifically: The waste PET alcoholysis solution is mixed with the polyurethane prepolymer, and chain extension stirring reaction is carried out, and then the mixture is dried at 60 DEG C for 24h to obtain the polyurethane adhesive; The mass ratio of the waste PET alcoholysis solution to the polyurethane prepolymer is 0.5:20; The reaction temperature is 80 DEG C, the reaction time is 2h, and the stirring speed is 300r / min.

[0033] In the preparation method, the waste PET alcoholysis product is used to synthesize the polyurethane adhesive, the overall system temperature of the reaction is low, and the operability is good.

[0034] Example 5 By Figure 1 It can be known from infrared spectrum detection and analysis that the PET alcoholysis product has transmission peaks at 3300-3550cm -1 and 1030 cm -1 , the peak value is the characteristic peak of hydroxyl group (—OH), and the characteristic peak intensity is high, which represents that the alcoholysis product contains a large amount of hydroxyl group. It can be seen from the infrared spectrum of PU-GOP that PU-GOP has transmission peaks at N-H 3328-3354 cm -1 and 1544 cm -1 , the peak value is the characteristic peak of amino group (—NH—), which represents the stretching vibration of —NH—, and the transmission peak observed in the range of 1695-1730 cm -1 corresponds to the stretching vibration of C=O, which indicates that the isocyanate group (—NCO—) of IPDI reacts with —OH of PPG to generate the amino acid ester group NHCOO—. In addition, the polyurethane infrared spectrum has a transmission peak at 2270 cm -1No characteristic peaks of -NCO were found nearby, indicating that -NCO had completely reacted with the -OH in the degradation products of the chain extender PET. In summary, polyurethane was successfully prepared.

[0035] from Figure 2 The viscosity curve of PU-GOP dynamic rheological testing as a function of temperature shows that the adhesive has the highest viscosity at 0℃, and the viscosity decreases as the temperature increases. Simultaneously, the overall viscosity of the polyurethane adhesive increases with increasing R value, indicating that the increased hard segment content affects the adhesive system. At room temperature (around 25℃), the viscosity of polyurethane can reach... . Figure 3 The storage modulus and loss modulus curves as a function of strain show that polyurethane exhibits high energy density under strain conditions. The energy storage modulus and loss modulus are both in a stable state, representing that the ability to store elastic deformation energy and the ability of the material to dissipate deformation energy are stable.

[0036] Combination Figure 4 Analysis of the TG and DTG curves of PU-GOP thermal decomposition performance shows that as the temperature increases, the thermal decomposition of PU-GOP can be divided into two stages: the first stage is 253-329 °C; the second stage is 329-412 °C. Figure 5 The DSC curves show that the glass transition temperature (Tg) increases with increasing R value, reaching 24.3 °C, 30.3 °C, and 33.1 °C respectively. This indicates that increasing the R value affects the polyurethane hard segment.

[0037] Example 6 Figure 6is the lap shear strength diagram of the polyurethane adhesive of the present application on different substrates. Wood, glass, paper, plastic and steel are selected as the adhesive substrate to carry out lap shear strength bonding test. PU-GOP shows stronger adhesion to cellulose-based materials such as wood and paper. The polar group urethane group in PU-GOP can react with the hydroxyl group in the cellulose molecule to form hydrogen bond, which is the main reason for its excellent adhesion performance. In addition, the porous structure of wood can make the flexibility of PU-GOP molecular chain so that it can fully penetrate and form mechanical interlocking effect, thus improving the interfacial bonding strength. For inorganic substrates such as glass and steel, the adhesion of PU-GOP is mainly formed by van der Waals force or dipole-dipole interaction. Although the strength of these interactions is lower than that of hydrogen bond, the benzene ring structure in PU-GOP molecule can produce π-π stacking effect with the substrate surface, thereby improving the adhesion performance. It is worth noting that the adhesion on plastic substrate is relatively low, which may be due to the low surface energy and non-polar characteristics of plastic surface limiting the interfacial interaction. The lap shear strength of PU-GOP on different substrates will increase with the increase of isocyanate index (R). With the increase of the value, the content of isocyanate group in the system increases, which not only increases the reaction site with the hydroxyl group in the chain extender GLP, promotes the formation of more dense crosslinked network, but also produces more urethane groups, promotes the interfacial interaction between the adhesive and the substrate surface. R is the lap shear strength diagram of the polyurethane adhesive of the present application on different substrates. Wood, glass, paper, plastic and steel are selected as the adhesive substrate to carry out lap shear strength bonding test. PU-GOP shows stronger adhesion to cellulose-based materials such as wood and paper. The polar group urethane group in PU-GOP can react with the hydroxyl group in the cellulose molecule to form hydrogen bond, which is the main reason for its excellent adhesion performance. In addition, the porous structure of wood can make the flexibility of PU-GOP molecular chain so that it can fully penetrate and form mechanical interlocking effect, thus improving the interfacial bonding strength. For inorganic substrates such as glass and steel, the adhesion of PU-GOP is mainly formed by van der Waals force or dipole-dipole interaction. Although the strength of these interactions is lower than that of hydrogen bond, the benzene ring structure in PU-GOP molecule can produce π-π stacking effect with the substrate surface, thereby improving the adhesion performance. It is worth noting that the adhesion on plastic substrate is relatively low, which may be due to the low surface energy and non-polar characteristics of plastic surface limiting the interfacial interaction. The lap shear strength of PU-GOP on different substrates will increase with the increase of isocyanate index (R). With the increase of the value, the content of isocyanate group in the system increases, which not only increases the reaction site with the hydroxyl group in the chain extender GLP, promotes the formation of more dense crosslinked network, but also produces more urethane groups, promotes the interfacial interaction between the adhesive and the substrate surface. R is the lap shear strength diagram of the polyurethane adhesive of the present application on different substrates. Wood, glass, paper, plastic and steel are selected as the adhesive substrate to carry out lap shear strength bonding test. PU-GOP shows stronger adhesion to cellulose-based materials such as wood and paper. The polar group urethane group in PU-GOP can react with the hydroxyl group in the cellulose molecule to form hydrogen bond, which is the main reason for its excellent adhesion performance. In addition, the porous structure of wood can make the flexibility of PU-GOP molecular chain so that it can fully penetrate and form mechanical interlocking effect, thus improving the interfacial

Claims

1. A method for preparing chain-extended polyurethane adhesives using waste PET degradation products, characterized in that, The specific steps are as follows: Step 1: Prepare waste PET alcoholysis solution; Step 2: Prepare NCO-terminated polyurethane prepolymer by reacting PPG and IPDI; Step 3: The waste PET alcoholysis liquid prepared in Step 1 is added to the polyurethane prepolymer as a chain extender to generate polyurethane adhesive.

2. The method for preparing chain-extended polyurethane adhesives using waste PET degradation products as described in claim 1, characterized in that, In step 1, specifically: Step 1.1: Pre-treat the waste PET plastic: Waste PET plastic is cut into fragments, soaked in HCl solution and stirred for 10-12 minutes, then filtered out and rinsed with deionized water; then soaked in NaOH solution and stirred for 10-12 minutes, filtered out and rinsed with deionized water; finally, placed in a forced-air drying oven and dried at 50-55℃ to obtain pretreated waste PET plastic sheets. Step 1.2: Dissolve the pretreated waste PET plastic sheets in a mixture of 1,4-butynediol and 1,4-cyclohexanediol, stir in an oil bath to carry out alcoholysis reaction, add zinc oxide and continue the reaction, then freeze recrystallize, extract with boiling water, and filter out the residue to obtain waste PET alcoholysis solution.

3. The method for preparing chain-extended polyurethane adhesives using waste PET degradation products as described in claim 2, characterized in that, In step 1.2, the mass ratio of waste PET plastic sheet, 1,4-butynediol, and 1,4-cyclohexanediol is 1-1.1:1:1; the mass of zinc oxide is 1-1.5% of the mass of waste PET plastic sheet.

4. The method for preparing chain-extended polyurethane adhesives using waste PET degradation products as described in claim 2, characterized in that, In step 1.2, the reaction process is as follows: first, adjust the oil bath temperature to 160-165℃ and the stirring speed to 250-255 r / min, and react for 1-1.5 h. After adding zinc oxide, adjust the oil bath temperature to 180-185℃ and the stirring speed to 400-405 r / min, and react for 3.5-4 h. Then, keep the oil bath temperature constant and adjust the stirring speed to 500-505 r / min, and continue the reaction for 35-40 min.

5. The method for preparing chain-extended polyurethane adhesives using waste PET degradation products as described in claim 2, characterized in that, In step 1.2, the freezing recrystallization temperature is -10~0℃, and the time is 24-25h.

6. The method for preparing chain-extended polyurethane adhesives using waste PET degradation products as described in claim 1, characterized in that, Step 2 specifically involves: PPG was vacuum dried in a vacuum drying oven, then IPDI was added, and the mixture was placed in a water bath for reflux and stirring. The reaction temperature was 80-85℃, the reaction time was 1-1.5h, and the stirring speed was 250-255r / min. Then, dibutyltin dilaurate was added as a catalyst, and the reaction was continued for 2-2.5h to generate a polyurethane prepolymer from PPG and IPDI.

7. The method for preparing chain-extended polyurethane adhesives using waste PET degradation products as described in claim 6, characterized in that, The molar ratio of isocyanate groups to hydroxyl groups in IPDI is 2 / 3 to 2 / 5; the amount of dibutyltin dilaurate added is 0.5-1% of the mass of PPG.

8. The method for preparing chain-extended polyurethane adhesives using waste PET degradation products as described in claim 1, characterized in that, Step 3 specifically involves: Waste PET alcoholysis liquid was mixed with polyurethane prepolymer and subjected to chain extension stirring reaction at a temperature of 80-85℃ for 2-2.5h and a stirring speed of 300-305r / min. The mixture was then dried at 60℃ for 24h to obtain polyurethane adhesive.

9. The method for preparing chain-extended polyurethane adhesives using waste PET degradation products as described in claim 8, characterized in that, The mass ratio of waste PET alcoholysis liquid to polyurethane prepolymer is 0.5-1:20-25.

10. The polyurethane adhesive prepared by the method according to any one of claims 1-9.

Images