Polyurethane with double dynamic bonds as well as preparation method and application thereof

Abstract

The invention provides polyurethane with double dynamic bonds as well as a preparation method and application thereof, and relates to the technical field of high-molecular polymer materials. The invention provides a preparation method of polyurethane with double dynamic bonds, which comprises the following steps: reacting diisocyanate with oligomer diol to synthesize a prepolymer, adding micromolecular diol and micromolecular dihydrazine as chain extenders, and reacting to obtain the polyurethane with double dynamic bonds. And reacting to form polyurethane with double dynamic bonds of semicarbazide bonds and phenolic hydroxyl carbamate bonds. The prepared polyurethane can passivate cracks, and due to the existence of dynamic bonds in the polyurethane, the polyurethane is endowed with good fatigue performance and excellent recycling capacity. The polyurethane prepared by the invention has excellent mechanical property, ultrahigh fracture energy and excellent fatigue property, and compared with a traditional polyurethane material, the polyurethane with ultrahigh fracture energy has a wide prospect in the engineering application fields such as sealing rings and the like.

Description

Technical Field

[0001] The invention relates to the technical field of high molecular polymer materials, and in particular to a polyurethane with double dynamic bonds and a preparation method and application thereof. Background Art

[0002] As a high-performance elastomer, polyurethane materials are widely used as dynamic sealing materials in the fields of aerospace, ocean, etc. However, existing polyurethane dynamic sealing materials generally have the problem of poor fracture energy. In engineering applications, notches are easily formed due to friction and wear, resulting in poor mechanical properties of the product, which seriously shortens the service life of the product. This is a technical problem that needs to be solved in the construction of high-performance polyurethane materials. Summary of the invention

[0003] In view of this, the object of the present invention is to provide a polyurethane with double dynamic bonds and a preparation method and application thereof. The polyurethane with double dynamic bonds provided by the present invention has excellent mechanical properties, ultra-high fracture energy and excellent fatigue performance.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a polyurethane having a double dynamic bond, comprising the following steps:

[0006] The oligomer diol is mixed with diisocyanate to carry out prepolymerization reaction to obtain an isocyanate-terminated polyurethane prepolymer;

[0007] The isocyanate-terminated polyurethane prepolymer is mixed with a small molecule diol, a small molecule dihydrazine and an organic solvent to carry out a chain extension reaction to obtain the polyurethane with double dynamic bonds; the small molecule diol includes 4,4'-dihydroxybiphenyl.

[0008] Preferably, the oligomer diol includes polytetramethylene glycol and / or polycarbonate diol, and the number average molecular weight of the oligomer diol is 1000-2000.

[0009] Preferably, the diisocyanate includes one or more of toluene diisocyanate, diphenylmethane diisocyanate and hexamethylene diisocyanate.

[0010] Preferably, the molar ratio of the oligomer diol to the diisocyanate is 1:(1.5-3.5).

[0011] Preferably, the prepolymerization reaction is carried out at a temperature of 60 to 80° C. and for a time of 1 to 3 hours.

[0012] Preferably, the small molecule dihydrazine comprises isophthalic acid dihydrazide.

[0013] Preferably, the molar ratio of the small molecule diol to the small molecule dihydrazine is 1:3; and the ratio of the total molar amount of the small molecule diol and the small molecule dihydrazine to the molar amount of the diisocyanate is 1:2.

[0014] Preferably, the chain extension reaction is carried out at a temperature of 60 to 80° C. and for a time of 4 to 12 hours.

[0015] The present invention provides a polyurethane having double dynamic bonds prepared by the preparation method described in the above technical solution, wherein the double dynamic bonds include a semicarbazide bond and a phenolic hydroxyl carbamate bond.

[0016] The present invention provides the use of the polyurethane with double dynamic bonds described in the above technical solution in the preparation of dynamic sealing materials.

[0017] The invention provides a method for preparing polyurethane with dual dynamic bonds. The method firstly reacts diisocyanate and oligomer diol to synthesize prepolymer, then adds small molecule diol and small molecule dihydrazine as chain extenders, and reacts to form polyurethane with dual dynamic bonds of semicarbazide bond and phenolic hydroxyl carbamate bond. The polyurethane prepared by the invention can passivate cracks, and due to the presence of dynamic bonds, it is endowed with good fatigue performance and excellent recycling ability (such as re-filming after dissolving with organic solvents such as DMF). The polyurethane prepared by the invention has excellent mechanical properties, ultra-high fracture energy and excellent fatigue performance. Compared with traditional polyurethane materials, the polyurethane with ultra-high fracture energy has broad prospects in engineering application fields such as sealing rings.

[0018] The results of the examples show that the fracture energy of the polyurethane with double dynamic bonds prepared by the present invention is as high as 519.3 kJ·m -2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The mechanical properties of polyurethane products with different chain extender contents prepared in Example 1 and Comparative Examples 1 to 4;

[0020] Figure 2 The mechanical properties of polyurethane products with different isocyanates prepared in Examples 1 to 3;

[0021] Figure 3 This is the fracture energy diagram of the polyurethane product of Example 1;

[0022] Figure 4 This is the fracture energy diagram of the polyurethane product of Example 2;

[0023] Figure 5 The stress-strain curve of Example 2 after 100 cycles of 200%;

[0024] Figure 6The maximum stress of Example 2 after 100 cycles of 200%;

[0025] Figure 7 The invention discloses a process for preparing a polyurethane having double dynamic bonds and the reactions involved. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a polyurethane having a double dynamic bond, comprising the following steps:

[0027] The oligomer diol is mixed with diisocyanate to carry out prepolymerization reaction to obtain an isocyanate-terminated polyurethane prepolymer;

[0028] The isocyanate-terminated polyurethane prepolymer is mixed with a small molecule diol, a small molecule dihydrazine and an organic solvent to carry out a chain extension reaction to obtain the polyurethane with double dynamic bonds; the small molecule diol includes 4,4'-dihydroxybiphenyl.

[0029] In the present invention, unless otherwise specified, the raw materials involved are commercially available products well known in the art.

[0030] The present invention mixes oligomer diol and diisocyanate for prepolymerization to obtain an isocyanate-terminated polyurethane prepolymer. In the present invention, the oligomer diol preferably includes polytetrahydrofuran diol and / or polycarbonate diol, and the number average molecular weight of the oligomer diol is preferably 1000-2000. In the present invention, the diisocyanate preferably includes one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI). In the present invention, the molar ratio of the oligomer diol to the diisocyanate is preferably 1: (1.5-3.5), which can be 1: 1.5, 1: 2, 1: 2.5, 1: 3 or 1: 3.5. The present invention preferably adds diisocyanate to the oligomer diol.

[0031] In the present invention, the temperature of the prepolymerization reaction is preferably 60-80°C, which may be 60°C, 70°C or 80°C, and the time is preferably 1-3h, which may be 1h, 2h or 3h; the prepolymerization reaction is preferably carried out under a nitrogen atmosphere. In the present invention, -NCO in the diisocyanate reacts with -OH in the oligomer diol to form a polyurethane prepolymer, wherein the long-chain oligomer diol will bring better flexibility to the polyurethane.

[0032] After obtaining the isocyanate-terminated polyurethane prepolymer, the present invention mixes the isocyanate-terminated polyurethane prepolymer with small molecule diol, small molecule dihydrazine and organic solvent to carry out chain extension reaction to obtain the polyurethane with double dynamic bonds.

[0033] In the present invention, the organic solvent is preferably DMF. The present invention has no special requirements on the amount of the organic solvent, as long as the raw materials are fully dissolved.

[0034] In the present invention, the small molecule diol is preferably 4,4'-dihydroxybiphenyl (PPDP); the small molecule dihydrazine preferably includes isophthalic acid dihydrazide (IPDH); the molar ratio of the small molecule diol to the small molecule dihydrazine is preferably 1:3; the ratio of the total molar amount of the small molecule diol and the small molecule dihydrazine to the molar amount of diisocyanate is preferably 1:2.

[0035] In the present invention, the method of mixing the isocyanate-terminated polyurethane prepolymer with a small molecule diol, a small molecule dihydrazine and an organic solvent is preferably:

[0036] The isocyanate-terminated polyurethane prepolymer is dissolved in an organic solvent to obtain a dissolved isocyanate-terminated polyurethane prepolymer:

[0037] dissolving the small molecule diol in an organic solvent to obtain a small molecule diol solution;

[0038] Dissolving the small molecule dihydrazine in an organic solvent to obtain a small molecule dihydrazine solution;

[0039] At a temperature of 60 to 80° C., the small molecule diol solution is dripped into the dissolved isocyanate-terminated polyurethane prepolymer, and after the dripping is completed, the small molecule dihydrazine solution is added thereto; the dripping time is within 30 minutes.

[0040] In the present invention, the temperature of the chain extension reaction is preferably 60 to 80°C, which may be 60°C, 70°C or 80°C, and the time is preferably 4 to 12 hours, which may be 4 hours, 5 hours, 6 hours, 10 hours or 12 hours; the chain extension reaction is preferably carried out in a nitrogen atmosphere. During the chain extension reaction, the viscosity of the reaction system is preferably adjusted by adding DMF to prevent explosion. During the chain extension reaction, small molecule dihydrazine and small molecule diol react with isocyanate groups to generate semicarbazide bonds and phenolic hydroxyl carbamate bonds, respectively, introduce double dynamic bonds into the polyurethane structure, and form rigid segments of polyurethane.

[0041] After the chain extension reaction, the present invention also preferably degasses and heat cures the obtained reaction system in sequence to obtain the molded polyurethane with dual dynamic bonds. In the present invention, the degassing is preferably carried out under heating conditions, the heating temperature is preferably 80°C, and the degassing is preferably carried out in an oven. The present invention preferably pours the polyurethane solution obtained after the degassing into a hot mold, and then places it in an oven for heat curing, the temperature of the heat curing is preferably 80°C, and the time is preferably 48 to 72 hours; the solvent is removed simultaneously during the heat curing process.

[0042] Taking the oligomer diol as polytetrahydrofuran diol, the small molecule diol as 4,4'-dihydroxybiphenyl, and the small molecule dihydrazine as isophthalic acid dihydrazide as an example, the reaction involved in preparing the polyurethane with double dynamic bonds in the embodiment of the present invention is as follows: Figure 7 shown.

[0043] The present invention provides a polyurethane with dual dynamic bonds prepared by the preparation method described in the above technical solution, wherein the dual dynamic bonds include a semicarbazide bond and a phenolic hydroxyl carbamate bond. Generally, polyurethane, as a kind of elastomer, will greatly affect its service life once cracks occur, while the polyurethane with dual dynamic bonds provided by the present invention has the ability to passivate the notch, has excellent mechanical properties, and thus has superb performance in use.

[0044] Dynamic bonds can make materials have better performance. On the one hand, the cross-linked network formed can give the polymer excellent mechanical properties. On the other hand, the characteristics of dynamic bonds make it self-repairing, recyclable, and able to reconstruct the original performance. Therefore, the study of shape memory polyurethane materials containing dynamic bonds is expected to provide a high-performance dynamic sealing material. In addition, the characteristics of dynamic bonds enable further regulation of the mechanical properties and shape memory properties of shape memory polymers, providing a possibility for realizing adaptive sealing materials with self-recoverable sealing properties. The present invention studies shape memory polyurethanes with dynamic covalent bonds and dynamic non-covalent bonds with different activation energies, constructs the correlation between chemical bonds and the mechanical properties, shape memory properties, and sealing properties of polyurethane, reveals the mechanism of self-repairing of the sealing properties of intelligent sealing materials, and designs new methods for establishing dynamic sealing material systems suitable for high-end fields such as aerospace.

[0045] The present invention provides the use of the polyurethane with double dynamic bonds described in the above technical solution in the preparation of dynamic sealing materials. The present invention introduces two dynamic bonds, aminourea and phenolic hydroxycarbamate, into the polyurethane chain segment through reasonable molecular design, so that the polyurethane has ultra-high fracture energy and strong fatigue resistance and mechanical properties, which can solve the problem that the mechanical properties of the polyurethane dynamic sealing materials at this stage deteriorate due to friction and wear during use, resulting in notches.

[0046] In order to further illustrate the present invention, the polyurethane with double dynamic bonds provided by the present invention and its preparation method and application are described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present invention.

[0047] Example 1

[0048] A polyurethane with double dynamic bonds, the preparation steps are as follows:

[0049] Weigh 20 g of oligomer diol polytetrahydrofuran diol (Mn=2000) into a 500 mL three-necked flask with mechanical stirring, add 3.48 g of 2,4-diisocyanato-1-methylbenzene (TDI), and react at 80° C. under N2 protection for 2 h to obtain an -NCO-terminated polyurethane prepolymer;

[0050] Subsequently, 50 mL of DMF was added to a three-necked flask at 80° C. After the polyurethane prepolymer was fully dissolved, a small molecule diol, 4,4'-dihydroxybiphenyl (PPDP, 0.47 g), dissolved in 30 mL of DMF, was added dropwise within 30 min, and then a small molecule dihydrazine, isophthalic acid dihydrazide (IPDH, 1.46 g), dissolved in 30 mL of DMF was added, and the reaction was maintained at 80° C. The chain extension reaction was carried out under a nitrogen atmosphere for 10 h, and then the reaction was stopped. During this period, DMF (70 mL) was added to adjust the viscosity of the system to obtain a polyurethane solution;

[0051] The polyurethane solution was heated in an oven at 80°C to remove bubbles and poured into a hot mold, and then placed in an 80°C forced air oven to dry for 2 days for thermal curing, while removing the solvent DMF to obtain a polyurethane with dual dynamic bonds.

[0052] Example 2

[0053] Weigh 20 g of oligomer diol polytetrahydrofuran diol (Mn=2000) into a 500 mL three-necked flask with mechanical stirring, add 5.01 g of diphenylmethane diisocyanate (MDI), and react at 80° C. under N2 protection for 2 h to obtain an -NCO-terminated polyurethane prepolymer;

[0054] Subsequently, 50 mL of DMF was added to a three-necked flask at 80° C. After the polyurethane prepolymer was fully dissolved, PPDP (0.47 g) dissolved in 30 mL of DMF, a small molecule diol, was added dropwise within 30 min, and then IPDH (1.46 g) dissolved in 30 mL of DMF, a small molecule dihydrazine, was added. The reaction was maintained at 80° C. and the chain extension reaction was carried out under a nitrogen atmosphere for 10 h, and then the reaction was stopped. During this period, DMF (70 mL) was added to adjust the viscosity of the system to obtain a polyurethane solution.

[0055] The polyurethane solution was heated in an oven at 80°C to remove bubbles and poured into a hot mold, which was then placed in an air-blast oven at 80°C to dry for 2 days for thermal curing while removing the solvent DMF to obtain a polyurethane with dual dynamic bonds.

[0056] Example 3

[0057] Weigh 20 g of oligomer diol polytetrahydrofuran diol (Mn=2000) into a 500 mL three-necked flask with mechanical stirring, add 3.36 g of hexamethylene diisocyanate (HDI), and react at 80° C. under N2 protection for 2 h to obtain an -NCO-terminated polyurethane prepolymer;

[0058] Subsequently, 50 mL of DMF was added to a three-necked flask at 80° C. After the polyurethane prepolymer was fully dissolved, PPDP (0.47 g) dissolved in 30 mL of DMF, a small molecule diol, was added dropwise within 30 min, and then IPDH (1.46 g) dissolved in 30 mL of DMF, a small molecule dihydrazine, was added. The reaction was maintained at 80° C. and the chain extension reaction was carried out under a nitrogen atmosphere for 10 h, and then the reaction was stopped. During this period, DMF (70 mL) was added to adjust the viscosity of the system to obtain a polyurethane solution.

[0059] The polyurethane solution was heated in an oven at 80°C to remove bubbles and poured into a hot mold, which was then placed in an 80°C forced air oven to dry for 2 days for thermal curing while removing the solvent DMF to obtain a polyurethane with dual dynamic bonds.

[0060] Comparative Example 1

[0061] Weigh 20 g of oligomer diol polytetrahydrofuran diol (Mn=2000) into a 500 mL three-necked flask with mechanical stirring, add 3.48 g of TDI, and react at 80° C. under N2 protection for 2 h to obtain an -NCO-terminated polyurethane prepolymer;

[0062] Subsequently, 50 mL of DMF was added to a three-necked flask at 80° C. After the polyurethane prepolymer was fully dissolved, PPDP (1.86 g) dissolved in 60 mL of DMF was added and the addition was completed within 30 min. The reaction was maintained at 80° C. and the chain extension reaction was carried out under a nitrogen atmosphere for 10 h. The reaction was stopped and DMF (70 mL) was added during this period to adjust the viscosity of the system to obtain a polyurethane solution.

[0063] The polyurethane solution was heated in an oven at 80°C to remove bubbles and poured into a hot mold, which was then placed in an air-blast oven at 80°C to dry for 2 days for thermal curing while removing the solvent DMF to obtain a polyurethane product.

[0064] Comparative Example 2

[0065] Weigh 20 g of oligomer diol polytetrahydrofuran diol (Mn=2000) into a 500 mL three-necked flask with mechanical stirring, add 3.48 g of TDI, and react at 80° C. under N2 protection for 2 h to obtain an -NCO-terminated polyurethane prepolymer;

[0066] Subsequently, 50 mL of DMF was added to a three-necked flask at 80° C. After the polyurethane prepolymer was fully dissolved, PPDP (1.40 g) dissolved in 30 mL of DMF was added and the addition was completed within 30 min. Subsequently, IPDH (0.49 g) dissolved in 30 mL of DMF was added, and the reaction was maintained at 80° C. Under a nitrogen atmosphere, the chain extension reaction was carried out for 10 h, and then the reaction was stopped. During this period, DMF (70 mL) was added to adjust the viscosity of the system to obtain a polyurethane solution;

[0067] The polyurethane solution was heated in an oven at 80°C to remove bubbles and poured into a hot mold, which was then placed in an air-blast oven at 80°C to dry for 2 days for thermal curing while removing the solvent DMF to obtain a polyurethane product.

[0068] Comparative Example 3

[0069] Weigh 20 g of oligomer diol polytetrahydrofuran diol (Mn=2000) into a 500 mL three-necked flask with mechanical stirring, add 3.48 g of TDI, and react at 80° C. under N2 protection for 2 h to obtain an -NCO-terminated polyurethane prepolymer;

[0070] Subsequently, 50 mL of DMF was added to a three-necked flask at 80° C. After the polyurethane prepolymer was fully dissolved, PPDP (0.93 g) dissolved in 30 mL of DMF was added and the addition was completed within 30 min. Subsequently, IPDH (0.97 g) dissolved in 30 mL of DMF was added, and the reaction was maintained at 80° C. Under a nitrogen atmosphere, the chain extension reaction was carried out for 10 h, and then the reaction was stopped. During this period, DMF (70 mL) was added to adjust the viscosity of the system to obtain a polyurethane solution;

[0071] The polyurethane solution was heated in an oven at 80°C to remove bubbles and poured into a hot mold, which was then placed in an air-blast oven at 80°C to dry for 2 days for thermal curing while removing the solvent DMF to obtain a polyurethane product.

[0072] Comparative Example 4

[0073] Weigh 20 g of oligomer diol polytetrahydrofuran diol (Mn=2000) into a 500 mL three-necked flask with mechanical stirring, add 3.48 g of TDI, and react at 80° C. under N2 protection for 2 h to obtain an -NCO-terminated polyurethane prepolymer;

[0074] Subsequently, 50 mL of DMF was added to a three-necked flask at 80° C. After the polyurethane prepolymer was fully dissolved, IPDH (1.94 g) dissolved in 30 mL of DMF was added, and the reaction was maintained at 80° C. Under a nitrogen atmosphere, the chain extension reaction was carried out for 10 h, and then the reaction was stopped. During this period, DMF (70 mL) was added to adjust the viscosity of the system to obtain a polyurethane solution;

[0075] The polyurethane solution was heated in an oven at 80°C to remove bubbles and poured into a hot mold, which was then placed in an air-blast oven at 80°C to dry for 2 days for thermal curing while removing the solvent DMF to obtain a polyurethane product.

[0076] The polyurethane products prepared in the examples and comparative examples were tested for performance:

[0077] The mechanical properties of the polyurethane products prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were tested using an electronic universal testing machine at a tensile speed of 50 mm / min. The results are as follows: Figure 1 and Figure 2 The test data are shown in Table 1. Figure 1 and Figure 2 It can be seen that the tensile strength of Example 2 is the highest, and its toughness can be calculated and is also the highest among Examples 1 to 3, indicating that it has the best mechanical properties.

[0078] Table 1 Mechanical properties of polyurethane products prepared in Examples 1 to 3 and Comparative Examples 1 to 4

[0079]

[0080]

[0081] The fracture energy of the polyurethane products obtained in Examples 1 and 2 was tested at a tensile speed of 50 mm / min. The results are as follows: Figure 3 and Figure 4 shown. Figure 3 The fracture energy of the polyurethane product of Example 1 was calculated to be 185.6 kJ·m -2 ; Figure 4 The fracture energy of the polyurethane product of Example 2 was calculated to be 519.3 kJ·m -2 , which has the highest fracture energy among all polyurethane samples, indicating that it has a strong notch passivation ability.

[0082] The fatigue performance test of the polyurethane product prepared in Example 2 was carried out by stretching for 100 times at a stretching speed of 50 mm / min. Figure 5 and Figure 6 As shown, Figure 5 The stress-strain curve of Example 2 after 100 cycles of 200% (i.e., the sample length increases by 2 times) is shown below: Figure 6 The maximum stress of Example 2 after 100 cycles of 200% is Figure 5 and Figure 6 It can be seen that Example 2 has very good fatigue performance, so that its maximum stress does not change substantially starting from the 10th cycle.

[0083] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a polyurethane having a double dynamic bond, characterized in that: The following steps are involved: The oligomer diol is mixed with diisocyanate to carry out prepolymerization reaction to obtain an isocyanate-terminated polyurethane prepolymer; The isocyanate-terminated polyurethane prepolymer is mixed with a small molecule diol, a small molecule dihydrazine and an organic solvent to carry out a chain extension reaction to obtain the polyurethane with double dynamic bonds; the small molecule diol includes 4,4'-dihydroxybiphenyl.

2. The preparation method according to claim 1, characterized in that: The oligomer diol includes polytetramethylene glycol and / or polycarbonate diol, and the number average molecular weight of the oligomer diol is 1000-2000.

3. The preparation method according to claim 1, characterized in that: The diisocyanate includes one or more of toluene diisocyanate, diphenylmethane diisocyanate and hexamethylene diisocyanate.

4. The preparation method according to claim 1, 2 or 3, characterized in that: The molar ratio of the oligomer diol to the diisocyanate is 1:(1.5-3.5).

5. The preparation method according to claim 1, 2 or 3, characterized in that: The prepolymerization reaction temperature is 60-80° C. and the reaction time is 1-3 hours.

6. The preparation method according to claim 1, characterized in that: The small molecule dihydrazine includes isophthalic acid dihydrazide.

7. The preparation method according to claim 1 or 6, characterized in that: The molar ratio of the small molecule diol to the small molecule dihydrazine is 1:3; the ratio of the total molar amount of the small molecule diol and the small molecule dihydrazine to the molar amount of the diisocyanate is 1:

2.

8. The preparation method according to claim 1 or 6, characterized in that: The temperature of the chain extension reaction is 60-80° C. and the time is 4-12 hours.

9. The polyurethane having double dynamic bonds prepared by the preparation method according to any one of claims 1 to 8, wherein the double dynamic bonds include semicarbazide bonds and phenolic hydroxyl carbamate bonds.

10. Use of the polyurethane with double dynamic bonds according to claim 9 in the preparation of dynamic sealing materials.

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