A catalyst-activated degradable thermosetting polyurethane and a synthesis method thereof

Abstract

A degradable thermosetting polyurethane with a catalyst and a synthesis method thereof belong to the technical field of polymer materials. The present invention provides a degradable thermosetting polyurethane with a catalyst, and also provides a synthesis method thereof, which comprises the following steps: (1) adding polyisocyanate and a catalyst into a container, stirring evenly, and then adding polyol, stirring evenly and pre-curing; (2) pouring into an internal mixer and stirring after a gel state appears; (3) after the reaction is completed, cooling to room temperature, and crushing with a pulverizer to obtain white thermosetting polyurethane powder; (4) spraying a release agent into a square mold, after the release agent is dried, spreading the thermosetting polyurethane powder in the mold, transferring it to a hot press for hot pressing, cooling to room temperature after completion, and taking out the mold to obtain a sheet-like thermosetting polyurethane material. The thermosetting polyurethane of the present invention has higher fracture strength, lower activation energy, can relax in a short time, and has more efficient degradation ability.

Description

Technical Field

[0001] The present application belongs to the technical field of polymer materials, and specifically relates to a degradable thermosetting polyurethane with a catalyst and a synthesis method thereof. Background Art

[0002] Thermosetting polymers are widely used in aerospace, construction and various fields of daily life due to their excellent mechanical properties, stability and strong load-bearing capacity. The stable chemical cross-linking structure in traditional thermosetting polymers makes them difficult to degrade and recycle, which limits the service life of the material and causes certain environmental pollution and waste of resources. Thermoplastic polymers are usually linear polymer chains with limited molecular weight bound together by non-covalent intermolecular forces. Their essentially reversible properties make them recyclable and reprocessable. However, thermoplastic polymers have poor mechanical properties and stability. The emergence of dynamic covalent bonds shortens the boundary between thermosetting polymers and thermoplastic polymers and brings opportunities for the development of a new generation of smart polymers, including ester exchange, disulfide bonds, large hindered urea bonds, thiourethane bonds, etc. Thermosetting polymers based on dynamic covalent bonds retain the advantages of thermosetting materials themselves and make them recyclable and reprocessable like thermoplastic polymers. Under external stimuli (light, heat, pH, force, etc.), the dynamic covalent bonds in thermosetting polymers break and reorganize, causing the topological network structure to rearrange, ultimately giving the material new properties, such as degradation and recycling, reprocessing, multiple shape memory, self-healing, etc. When the external stimuli are eliminated, this type of polymer exhibits the stability of traditional thermosetting polymers.

[0003] Thermosetting polyurethane is a widely used polymer material. However, the dynamics of the carbamate bond itself is poor, which makes it difficult to degrade and recycle the polyurethane material. Especially for aliphatic thermosetting polyurethane materials, the temperature required for dynamic exchange is relatively high (>220℃), which limits its wider application. At present, there are several methods to improve the dynamics of polyurethane: introducing different substituents, free hydroxyl groups and other dynamic covalent bonds with strong dynamics (such as large hindered urea bonds, Diels-Alder reactions, etc.) into the polyurethane system; or converting the carbamate bond into an oxime urethane bond with strong dynamics to reduce the stability of the chemical bond. However, none of the above methods can fundamentally solve the problem of poor dynamics of polyurethane materials.

[0004] In order to recycle and degrade polyurethane materials on a large scale, regulating the dynamics of the carbamate bond itself is a more direct method. The introduction of catalysts provides an effective method for controlling the rate of dynamic exchange reactions, which has the universality of controlling topological structures. Based on this, we use different catalysts to regulate the rate of carbamate dynamic exchange reactions, essentially improving the poor dynamics of thermosetting polyurethane materials and the difficulty in degradation and recycling. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to design and provide a degradable thermosetting polyurethane with a catalyst and a synthesis method thereof. The present invention utilizes a catalyst to essentially regulate the dynamics of the thermosetting polyurethane and improve the degradation ability of the material.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0007] A catalyst-activated degradable thermosetting polyurethane, characterized in that it is prepared from polyisocyanate, catalyst and polyol;

[0008] The molar ratio of the polyisocyanate: catalyst: polyol is 78.15-117.23: 3.00-5.00: 78.15-117.23, wherein the molar ratio of the isocyanate group in the polyisocyanate to the hydroxyl group in the polyol is 1:1.

[0009] The catalyst-activated degradable thermosetting polyurethane is characterized in that the polyisocyanate comprises a mixture of any one or more of hexamethylene diisocyanate trimer, toluene diisocyanate trimer, hexamethylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4-diisocyanate, L-lysine diisocyanate, and toluene diisocyanate.

[0010] The degradable thermosetting polyurethane with a catalyst is characterized in that the catalyst includes a mixture of any one or more of N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N',N'-tetramethylalkylenediamine, triethylamine, N,N-dimethylbenzylamine, solid amine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, triethanolamine, DMEA, pyridine, N,N'-dimethylpyridine, 1 5 7-triazidobicyclo(4.4.0)dec-5-ene, 1,8-diazabicycloundec-7-ene, dibutyltin dilaurate, stannous octoate, bismuth diethylhexanoate, zinc isooctanoate, bismuth isooctanoate, lead isooctanoate, mercury isooctanoate, bismuth neodecanoate, zinc neodecanoate, zirconium isooctanoate, and phenylmercury neodecanoate.

[0011] The degradable thermosetting polyurethane with a catalyst is characterized in that the polyol includes a mixture of any one or more of pentaerythritol, glycerol, trimethylolethane, xylitol, sorbitol, trimethylolpropane, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, and dipropylene glycol.

[0012] A method for synthesizing a degradable thermosetting polyurethane with a catalyst, characterized by comprising the following steps:

[0013] (1) Add polyisocyanate and catalyst into a container, stir evenly, then add polyol, stir evenly, and place in an oven at 60-120° C. for pre-curing;

[0014] (2) After the mixed system becomes gradually clear and transparent and hardens, pour it into a 60-120°C internal mixer and stir for 3-8 hours;

[0015] (3) After the reaction is completed, the temperature is lowered to room temperature, the product is taken out, and crushed using a crusher to obtain a white thermosetting polyurethane powder;

[0016] (4) Spray a release agent evenly onto the square mold. After the release agent is dry, weigh the thermosetting polyurethane powder obtained in step (3) and spread it evenly on the mold, and transfer it to a hot press for hot pressing. After the hot pressing is completed, turn on the cooling water button, and take out the mold after cooling to room temperature to obtain a sheet of thermosetting polyurethane material.

[0017] The synthesis method is characterized in that in the step (1), the molar ratio of polyisocyanate: catalyst: polyol is 78.15-117.23: 3.00-5.00: 78.15-117.23, wherein the molar ratio of isocyanate groups in the polyisocyanate to hydroxyl groups in the polyol is 1:1.

[0018] The synthesis method is characterized in that the polyisocyanate in step (1) includes a mixture of any one or more of hexamethylene diisocyanate trimer, toluene diisocyanate trimer, hexamethylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4-diisocyanate, L-lysine diisocyanate, and toluene diisocyanate.

[0019] The synthesis method is characterized in that the catalyst in step (1) comprises a mixture of any one or more of N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N',N'-tetramethylalkylenediamine, triethylamine, N,N-dimethylbenzylamine, solid amine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, triethanolamine, DMEA, pyridine, N,N'-dimethylpyridine, 1 5 7-triazidobicyclo(4.4.0)dec-5-ene, 1,8-diazabicycloundec-7-ene, dibutyltin dilaurate, stannous octoate, bismuth diethylhexanoate, zinc isooctanoate, bismuth isooctanoate, lead isooctanoate, mercury isooctanoate, bismuth neodecanoate, zinc neodecanoate, zirconium isooctanoate, and phenylmercury neodecanoate.

[0020] The synthesis method is characterized in that the polyol in step (1) includes a mixture of any one or more of pentaerythritol, glycerol, trimethylolethane, xylitol, sorbitol, trimethylolpropane, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, and dipropylene glycol.

[0021] The synthesis method is characterized in that the operation method of hot pressing in step (4) is specifically: preheating at 190°C for 20 minutes, increasing the pressure to 3MPa and hot pressing for 0.5h, continuing to increase the pressure to 4MPa and hot pressing for 0.5h, increasing the pressure to 5MPa and hot pressing for 0.5h, hot pressing at 6MPa for 1.5h, and ending the hot pressing.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The thermosetting polyurethane synthesized by the present invention has higher breaking strength than the thermosetting polyurethane without catalyst without affecting the breaking elongation of the material.

[0024] (2) The thermosetting polyurethane synthesized by the present invention has lower activation energy than thermosetting polyurethane without a catalyst and can relax in a short time.

[0025] (3) The thermosetting polyurethane synthesized by the present invention has more efficient degradation ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The stress-strain curve of the thermosetting polyurethane film of the product prepared in Examples 1-4;

[0027] Figure 2 The stress relaxation diagram and activation energy linear fitting curve of the thermosetting polyurethane film of the product prepared in Examples 1-4;

[0028] Figure 3This is a degradation diagram of the thermosetting polyurethane film of the product prepared in Example 1-4 (degradation conditions: catalyst in ethylene glycol N-methylpyrrolidone solution, catalyst concentration is 5 wt %, reaction at 120° C. for 24 h). DETAILED DESCRIPTION

[0029] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. According to these detailed descriptions, those skilled in the art can clearly understand the present invention and can implement the present invention. Without violating the principles of the present invention, the features in different embodiments can be combined to obtain new implementations, or certain features in certain embodiments can be replaced to obtain other preferred implementations.

[0030] The present invention will be further described in the following examples, which are intended only to provide a better understanding of the purpose of the present invention rather than to limit the scope of protection of the present invention.

[0031] Embodiment 1:

[0032] A method for synthesizing a degradable thermosetting polyurethane with a catalyst comprises the following steps:

[0033] (1) Add (39.51 g, 78.15 mmol) hexamethylene diisocyanate trimer (THDI) and (4.69 mmol, 2 mol%) 1,5,7-triazidobicyclo (4.4.0) dec-5-ene to a 50 mL beaker and stir evenly with a glass rod. Weigh (10.49 g, 78.15 mmol) trimethylolpropane (TMP) into a beaker, stir evenly, and place in a 90°C oven for pre-curing.

[0034] (2) After the mixed system in step (1) gradually becomes clear and transparent and hardens, pour it into a 90°C internal mixer and stir for 6 hours.

[0035] (3) After the reaction in step (2) is completed, the temperature is lowered to room temperature, the product is taken out, and pulverized using a pulverizer to obtain a white powder of thermosetting polyurethane.

[0036] (4) Spray the release agent evenly on the square mold. After the release agent is dry, weigh 4.00g of thermosetting polyurethane powder and spread it flat in the mold. Transfer it to a hot press and preheat it at 190°C for 20 minutes. Increase the pressure to 3MPa and press for 0.5h. Continue to increase the pressure to 4MPa and press for 0.5h. Increase the pressure to 5MPa and press for 0.5h. Then, press at 6MPa for 1.5h. After the hot press is completed, turn on the cooling water button, and remove the mold after cooling to room temperature to obtain a thermosetting polyurethane sheet material.

[0037] Embodiment 2:

[0038] A method for synthesizing a degradable thermosetting polyurethane with a catalyst comprises the following steps:

[0039] (1) Add (39.51 g, 78.15 mmol) of hexamethylene diisocyanate trimer (THDI) and (4.69 mmol, 2 mol%) of 1,8-diazabicycloundec-7-ene to a 50 mL beaker and stir evenly with a glass rod. Weigh (10.49 g, 78.15 mmol) of trimethylolpropane (TMP) into a beaker, stir evenly, and place in a 90°C oven for pre-curing.

[0040] (2) After the mixed system in step 1 gradually becomes clear and transparent and hardens, pour it into a 90°C internal mixer and stir for 6 hours.

[0041] (3) After the reaction in step (2) is completed, the temperature is lowered to room temperature, the product is taken out, and pulverized using a pulverizer to obtain a white powder of thermosetting polyurethane.

[0042] (4) Spray the release agent evenly on the square mold. After the release agent is dry, weigh 4.00g of thermosetting polyurethane powder and spread it flat in the mold. Transfer it to a hot press and preheat it at 190°C for 20 minutes. Increase the pressure to 3MPa and press for 0.5h. Continue to increase the pressure to 4MPa and press for 0.5h. Increase the pressure to 5MPa and press for 0.5h. Then, press at 6MPa for 1.5h. After the hot press is completed, turn on the cooling water button, and remove the mold after cooling to room temperature to obtain a thermosetting polyurethane sheet material.

[0043] Embodiment 3:

[0044] A method for synthesizing a degradable thermosetting polyurethane with a catalyst comprises the following steps:

[0045] (1) Add (39.51 g, 78.15 mmol) of hexamethylene diisocyanate trimer (THDI) and (4.69 mmol, 2 mol%) of dibutyltin dilaurate into a 50 mL beaker and stir evenly with a glass rod. Weigh (10.49 g, 78.15 mmol) of trimethylolpropane (TMP) into a beaker, stir evenly, and place in a 90°C oven for pre-curing.

[0046] (2) After the mixed system in step (1) gradually becomes clear and transparent and hardens, pour it into a 90°C internal mixer and stir for 6 hours.

[0047] (3) After the above reaction is completed, the temperature is lowered to room temperature, the product is taken out, and pulverized using a pulverizer to obtain a white powder of thermosetting polyurethane.

[0048] (4) Spray the release agent evenly on the square mold. After the release agent is dry, weigh 4.00g of thermosetting polyurethane powder and spread it flat in the mold. Transfer it to a hot press and preheat it at 190°C for 20 minutes. Increase the pressure to 3MPa and press for 0.5h. Continue to increase the pressure to 4MPa and press for 0.5h. Increase the pressure to 5MPa and press for 0.5h. Then, press at 6MPa for 1.5h. After the hot press is completed, turn on the cooling water button, and remove the mold after cooling to room temperature to obtain a thermosetting polyurethane sheet material.

[0049] Embodiment 4:

[0050] The conventional method for synthesizing thermosetting polyurethane without catalyst comprises the following steps:

[0051] (1) In a 50 mL beaker, add (39.51 g, 78.15 mmol) of hexamethylene diisocyanate trimer (THDI) and (10.49 g, 78.15 mmol) of trimethylolpropane (TMP) into the beaker, stir evenly with a glass rod, and place in a 90° C. oven for pre-curing.

[0052] (2) After the mixed system in step (1) gradually becomes clear and transparent and hardens, pour it into a 90°C internal mixer and stir for 6 hours.

[0053] (3) After the above reaction is completed, the temperature is lowered to room temperature, the product is taken out, and pulverized using a pulverizer to obtain a white powder of thermosetting polyurethane.

[0054] (4) Spray the release agent evenly on the square mold. After the release agent is dry, weigh 4.00g of thermosetting polyurethane powder and spread it flat in the mold. Transfer it to a hot press and preheat it at 190°C for 20 minutes. Increase the pressure to 3MPa and press for 0.5h. Continue to increase the pressure to 4MPa and press for 0.5h. Increase the pressure to 5MPa and press for 0.5h. Then, press at 6MPa for 1.5h. After the hot press is completed, turn on the cooling water button, and remove the mold after cooling to room temperature to obtain a thermosetting polyurethane sheet material.

[0055] like Figure 1 As shown, the stress-strain curves of the thermosetting polyurethane films of the products prepared in Examples 1-4 illustrate that the synthesized thermosetting polyurethanes all exhibit strong and hard characteristics, and their elongation at break is about 13%. Compared with the system without catalyst action, the introduction of catalyst can greatly improve the fracture strength of the material while keeping the elongation at break of the material basically unchanged. Among them, the thermosetting polyurethane synthesized in Example 1 has the highest fracture strength of 87.7MPa, and the thermosetting polyurethane without catalyst action (Example 4) has the lowest fracture strength of 62.6MPa.

[0056] like Figure 2As shown in the figure, the stress relaxation diagrams and activation energy linear fitting curves of the thermosetting polyurethane films of the products prepared in Examples 1-4 show that at 200°C, the thermosetting polyurethanes synthesized in Examples 1, 2 and 3 can relax to the characteristic relaxation time within 120 seconds, while the thermosetting polyurethane synthesized without a catalyst (Example 4) requires 3200 seconds. The above results show that the addition of a catalyst can effectively increase the dynamic exchange rate of urethane bonds.

[0057] Degradation test conditions: catalyst concentration is 5wt% in N-methylpyrrolidone solution of ethylene glycol, reaction time is 24h at 120℃. Figure 3 As shown in the figure, the degradation diagrams of the thermosetting polyurethane films of the products prepared in Examples 1-4 show that the thermosetting polyurethanes synthesized in Examples 1 and 2 are completely degraded into clear and transparent solutions, while the degradation solution of the thermosetting polyurethane synthesized in Example 3 becomes turbid after heating for 24 hours, and the film still exists. The thermosetting polyurethane without the action of the catalyst (Example 4) did not degrade after 24 hours, indicating that the introduction of the catalyst can effectively improve the degradation ability of the thermosetting polyurethane.

[0058] Table 1 shows the mechanical data and activation energy of thermoplastic polyurethane films of Examples 1-4, which shows that the activation energy of thermosetting polyurethane without catalyst (Example 4) is 246.1 kJ·mol -1 , while the activation energy of the thermosetting polyurethanes (Examples 1 to 3) under the action of the catalyst can be reduced to below 180 kJ / mol. And the thermosetting polyurethane synthesized in Example 2 has the lowest activation energy, which is 159.0 kJ·mol -1 , indicating that the catalyst can effectively improve the dynamics of the carbamate bond and effectively reduce the activation energy of the carbamate bond.

[0059] Table 1 Mechanical parameters of thermoplastic polyurethane films

[0060]

[0061] Although the present application is described above with reference to specific embodiments, it should be understood by those skilled in the art that many modifications may be made to the configurations and details disclosed in the present application within the principles and scope disclosed in the present application. The scope of protection of the present application is determined by the appended claims, and the claims are intended to cover all modifications included in the equivalent literal meaning or scope of the technical features in the claims.

Claims

1. A degradable thermosetting polyurethane with a catalyst, characterized in that Prepared from polyisocyanate, catalyst and polyol; The molar ratio of the polyisocyanate: catalyst: polyol is 78.15-117.23: 3.00-5.00: 78.15-117.23, wherein the molar ratio of the isocyanate group in the polyisocyanate to the hydroxyl group in the polyol is 1:1; The catalyst is a mixture of any one or more of N,N'-dimethylpyridine, 1,5,7-triazidobicyclo (4.4.0) dec-5-ene, 1,8-diazabicycloundec-7-ene, dibutyltin dilaurate, stannous octoate, bismuth isooctanoate or lead isooctanoate; The polyisocyanate is any one or more of hexamethylene diisocyanate trimer, toluene diisocyanate trimer or hexamethylene diisocyanate; The polyol is a mixture of any one or more of pentaerythritol, trimethylolethane, sorbitol, trimethylolpropane or glycerol.

2. The method for synthesizing a degradable thermosetting polyurethane with a catalyst as claimed in claim 1, characterized in that The following steps are involved: (1) Add polyisocyanate and catalyst into a container, stir evenly, then add polyol, stir evenly, and place in an oven at 60-120° C. for pre-curing; (2) After the mixed system becomes gradually clear and transparent and hardens, pour it into a 60-120°C internal mixer and stir for 3-8 hours; (3) After the reaction is completed, the temperature is lowered to room temperature, the product is taken out, and crushed using a crusher to obtain a white thermosetting polyurethane powder; (4) Spray a release agent evenly onto the square mold. After the release agent is dry, weigh the thermosetting polyurethane powder obtained in step (3) and spread it evenly on the mold, and transfer it to a hot press for hot pressing. After the hot pressing is completed, turn on the cooling water button, and take out the mold after cooling to room temperature to obtain a sheet of thermosetting polyurethane material.

3. The synthesis method as claimed in claim 2, characterized in that The specific operation method of hot pressing in step (4) is: preheating at 190°C for 20 minutes, increasing the pressure to 3MPa and hot pressing for 0.5h, continuing to increase the pressure to 4MPa and hot pressing for 0.5h, increasing the pressure to 5MPa and hot pressing for 0.5h, hot pressing at 6MPa for 1.5h, and ending the hot pressing.

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