High-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic disulfide acetal bond and method for preparing the same

Abstract

The application provides a high-strength high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing a dynamic dithio acetal bond and a preparation method thereof. The application uses a macromolecular polydimethylsiloxane as a soft segment, a diisocyanate and a 1,3-bis(hydroxypropyl)-tetramethyldisiloxane copolymer as a hard segment, and a multi-hydroxyl compound containing a dynamic dithio acetal bond as a crosslinking agent. The prepared elastomer has good mechanical properties and a high thermoplastic temperature and can be repeatedly processed. The preparation process is simple and feasible, the product has stable performance and good reproducibility, and is suitable for popularization and application.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic disulfide acetal bond and a preparation method thereof, and belongs to the technical field of high polymer material synthesis. BACKGROUND

[0002] Polyurethane elastomer is a kind of elastic polymer material containing more urethane units in the molecular chain, which is usually prepared by polymerization reaction of low polymer polyol, polyisocyanate, chain extender and crosslinking agent. It has high elasticity and strength, outstanding wear resistance, and good oil resistance, chemical resistance and impact resistance. Among them, thermoplastic polyurethane elastomer (TPU) is a kind of block linear polymer, which is composed of short-chain low molecular weight diol as soft segment and dense urethane structure formed by diisocyanate and diol chain extender as hard segment. There is only physical crosslinking or light chemical crosslinking between molecular chains. This crosslinking method has reversibility, the intermolecular interaction is weakened during thermal processing, and the modulus is reduced, thereby giving the material the property of thermoplastic forming, making it suitable for the same mass production equipment and process as thermoplastic plastics. Due to its excellent comprehensive performance and green and environmentally friendly processing and molding method, thermoplastic polyurethane elastomer is widely used in many fields such as automobiles, cables, clothing, films and pipes, wires and other fields. However, the traditional thermoplastic polyurethane elastomer has some shortcomings that limit its application, such as containing toxic small molecules with odor, poor surface performance, poor weather resistance and yellowing resistance, general high temperature resistance, and general use temperature not exceeding 120℃. In order to overcome these shortcomings, people try to introduce polysiloxane with ideal weather resistance, high and low temperature resistance, chemical inertness and low surface tension into the molecular chain of thermoplastic polyurethane in a block polymerization manner to improve its performance. This kind of material is also called polysiloxane polyurethane thermoplastic elastomer.

[0003] In the above polysiloxane-modified polyurethane elastomers, the polysiloxane segments of the soft segments and the polyurethane of the hard segments will each form independent microdomains, where the soft segment microdomains provide flexibility and elasticity to the material, while the hard segment microdomains act as physical crosslinking points to provide strength and hardness to the material, and their phase transition temperature directly affects the thermoplastic temperature of the material. Due to the large difference in solubility parameter between the polysiloxane segments and the polyurethane, the soft and hard microdomains have poor compatibility and tend to further segregate to form macroscopic phase separation, making the mechanical properties of silicone-modified polyurethane with polysiloxane as the soft segment generally low, and it is difficult to exert the performance advantages of polyurethane materials. In order to solve the compatibility problem, one method is to introduce a second macromolecular diol such as polyether, polyester, polybutadiene, etc. as a transition segment in the soft segment to improve the phase separation phenomenon between polysiloxane and polyurethane. For example, Chinese patent document CN117603427A obtains wear-resistant and toughened silicone polyurethane by simultaneously introducing polylactic acid polyol and polysiloxane into the polyurethane; patent CN118930873A prepares a polyurethane elastomer with good low-temperature resilience and aging resistance by reacting carboxyl-terminated polybutadiene with polysiloxane diol, followed by preparing a block copolymer as a macromolecular diol; patent CN114891184A uses polytetrahydrofuran diol and hydroxyl-terminated polysiloxane as mixed soft segments, and adds a flame retardant to prepare a silicone polyurethane with flame retardant properties. But this way needs to add a lot of carbon chain macromolecular diol, often more than the content of polysiloxane in the soft segment, which also makes it difficult to reflect the advantages of polysiloxane in the material, and these studies do not focus on the thermoplastic temperature of the material. Another solution is to introduce disiloxane small molecules into the hard segment to improve compatibility by reducing the solubility parameter of the hard segment. In the document "Eur. Polym. J., 198 (2023), 112416", bis(hydroxyethyl sulfide ethyl)-tetramethyl disiloxane and 4,4'-methylene diphenyl diisocyanate (MDI) are used as raw materials to synthesize a hard segment with a crystallization temperature of 60°C, which effectively improves the compatibility of the soft and hard segments and improves the mechanical properties. However, such materials are subject to the structure of the hard segment, and it is difficult to form a tightly arranged hard segment microdomain, and the thermoplastic temperature is difficult to improve.

[0004] With the increasing requirements for material performance in industrial production and social development, there is an urgent need to develop a silicone polyurethane thermoplastic elastomer with excellent mechanical properties, high service temperature, and repeatable processing. This requires the material to maintain good dimensional stability at high working temperatures, i.e., high plasticization temperature. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithio acetal bond and a preparation method thereof. The present application uses macromolecular polydimethylsiloxane as the soft segment, diisocyanate and 1,3-bis(hydroxypropyl)-tetramethyldisiloxane copolymer as the hard segment, and a multi-hydroxyl compound containing dynamic dithio acetal bond as the crosslinking agent. The prepared elastomer has good mechanical properties and high thermoplastic temperature, and can be repeatedly processed. The preparation process is simple and feasible, the product performance is stable, the reproducibility is good, and the present application is suitable for popularization and application.

[0006] The technical scheme of the present application is as follows:

[0007] A preparation method of a high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithio acetal bond, comprising the following steps:

[0008] (1) 1,2-dibromoethane and p-hydroxybenzaldehyde are reacted in a mixed solvent of anhydrous ethanol and water in the presence of sodium hydroxide to obtain 1,2-bis(4-aldehyde phenoxy)ethane; 1,2-bis(4-aldehyde phenoxy)ethane and 2-mercaptoethanol are reacted in tetrahydrofuran in the presence of zirconium chloride to obtain a multi-hydroxyl compound containing dithio acetal bond;

[0009] (2) Diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane are reacted in solvent A to obtain a solution of isocyanate-terminated prepolymer X; 1,3-bis(hydroxypropyl)-tetramethyldisiloxane and stannous isooctoate are dispersed in solvent B to obtain solution Y; the solution of isocyanate-terminated prepolymer X is mixed with solution Y, and reacted to obtain a solution of polysiloxane polyurethane polymer Z;

[0010] (3) The multi-hydroxyl compound containing dithio acetal bond and the solution of polysiloxane polyurethane polymer Z are mixed, reacted, and solidified to obtain a high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithio acetal bond.

[0011] According to the present application, in step (1), the molar ratio of 1,2-dibromoethane to p-hydroxybenzaldehyde is 1:(2-2.3); the volume ratio of water to anhydrous ethanol is 1:(0.6-4); the mass ratio of p-hydroxybenzaldehyde to the mixed solvent is 1g:(3-8)ml; and the molar ratio of p-hydroxybenzaldehyde to sodium hydroxide is 1:(1-1.2).

[0012] According to the present application, in step (1), 1,2-dibromoethane is added to the reaction system in a dropwise manner.

[0013] According to the application, preferably, in step (1), the reaction temperature of 1,2-dibromoethane and p-hydroxybenzaldehyde is 55-85℃, the reaction time is 16-24h, and the reaction is carried out under the protection of protective gas and stirring.

[0014] According to the application, preferably, in step (1), the reaction liquid obtained by the reaction of 1,2-dibromoethane and p-hydroxybenzaldehyde is treated as follows: the reaction liquid is cooled to 0℃, the precipitate is filtered and washed with ethanol to obtain 1,2-bis(4-formylphenoxy)ethane.

[0015] According to the application, preferably, in step (1), the molar ratio of 1,2-bis(4-formylphenoxy)ethane to 2-mercaptoethanol is 1:(2-2.3), the mass of 1,2-bis(4-formylphenoxy)ethane to the volume of tetrahydrofuran is 1g:(5-20)ml, and the mass ratio of 1,2-bis(4-formylphenoxy)ethane to zirconium chloride is 1:(0.01-0.05).

[0016] According to the application, preferably, in step (1), the reaction temperature of 1,2-bis(4-formylphenoxy)ethane and 2-mercaptoethanol is 15-60℃, and the reaction time is 2-8h, and the reaction is carried out under stirring.

[0017] According to the application, preferably, in step (1), the reaction liquid obtained by the reaction of 1,2-bis(4-formylphenoxy)ethane and 2-mercaptoethanol is treated as follows: dichloromethane is added to the reaction liquid to precipitate, the precipitate is filtered; the precipitate is dissolved in tetrahydrofuran, dichloromethane is added, the precipitate is filtered and dried to obtain a polyhydroxyl compound containing a dithioacetal bond.

[0018] According to the application, preferably, in step (1), the polyhydroxyl compound containing a dithioacetal bond (crosslinking agent C) has the structure shown in formula (I):

[0019]

[0020] According to the application, preferably, in step (2), the solvent A is selected from one of toluene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, methyl isobutyl ketone, γ-butyrolactone, dimethyl sulfoxide, acetonitrile, dioxane, xylene, isopropyl alcohol, dichloromethane, acetone, ethyl acetate or n-hexane. The volume ratio of the total mass of diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane to the solvent A is 1g:0.5-30ml, preferably 1g:0.5-18ml.

[0021] According to the application, preferably, in step (2), the diisocyanate is one or a combination of two or more of toluene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, methylcyclohexyl diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, p-phenylene diisocyanate, p-xylylene diisocyanate or tetramethylxylylene diisocyanate.

[0022] According to the application, preferably, in step (2), the molar ratio of the diisocyanate to the hydroxyethoxypropyl-terminated polydimethylsiloxane is (1-13):1, preferably (3.1-5.2):1.

[0023] According to the application, preferably, in step (2), the weight average molecular weight of the hydroxyethoxypropyl-terminated polydimethylsiloxane is 500-5000 g / mol.

[0024] According to the application, in step (2), the hydroxyethoxypropyl-terminated polydimethylsiloxane has the following structure shown in formula (II):

[0025]

[0026] According to the application, preferably, in step (2), the hydroxyethoxypropyl-terminated polydimethylsiloxane is added dropwise into the reaction system in the form of a hydroxyethoxypropyl-terminated polydimethylsiloxane solution under stirring and protection of a protective gas; the type of the solvent used for the hydroxyethoxypropyl-terminated polydimethylsiloxane solution is the same as that of solvent A, the concentration of the hydroxyethoxypropyl-terminated polydimethylsiloxane solution is 0.1-0.5 g / mL; and the protective gas is nitrogen or argon.

[0027] According to the application, preferably, in step (2), the reaction temperature of the diisocyanate and the hydroxyethoxypropyl-terminated polydimethylsiloxane is 50-100°C, preferably 70-90°C, and the reaction time is 30-600 min, preferably 100-360 min; and the reaction is carried out under stirring and protection of a protective gas; preferably, the protective gas is nitrogen or argon.

[0028] According to the application, preferably, in step (2), the preparation method of the solution of the isocyanate group-terminated prepolymer X comprises the following steps: mixing the diisocyanate and solvent A1, and adding dropwise a mixture of the hydroxyethoxypropyl-terminated polydimethylsiloxane and solvent A2 under stirring and protection of a protective gas, to obtain the solution of the isocyanate group-terminated prepolymer X through reaction; preferably, the types of solvent A1 and solvent A2 are the same as those of solvent A, and the total volume of solvent A1 and solvent A2 is the same as that of solvent A.

[0029] According to the present application, in step (2), the isocyanate-terminated prepolymer X has the following formula (III) structure:

[0030]

[0031] According to the present application, in step (2), the solvent B is selected from one of toluene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, methyl isobutyl ketone, gamma-butyrolactone, dimethyl sulfoxide, acetonitrile, dioxane, xylene, isopropyl alcohol, dichloromethane, acetone, ethyl acetate or n-hexane. The mass of 1,3-bis(hydroxypropyl)-tetramethyldisiloxane to the volume of solvent B is 1g:2-15ml, preferably 1g:2-10ml.

[0032] According to the present application, in step (2), the mass ratio of 1,3-bis(hydroxypropyl)-tetramethyldisiloxane to stannous octoate is 100:(0.05-5), preferably 100:(2-4.4).

[0033] According to the present application, in step (2), the molar ratio of diisocyanate to 1,3-bis(hydroxypropyl)-tetramethyldisiloxane is 1:(0.3-1), preferably 1:(0.47-0.7).

[0034] According to the present application, in step (2), the solution Y is added dropwise to the solution of isocyanate-terminated prepolymer X under the protection of protective gas and stirring. Preferably, the protective gas is nitrogen or argon.

[0035] According to the present application, in step (2), the reaction temperature of the solution of isocyanate-terminated prepolymer X to solution Y is 50-100℃, preferably 70-90℃, the reaction time is 30-480min, preferably 30-240min, and the reaction is carried out under stirring and protective gas protection; preferably, the protective gas is nitrogen or argon.

[0036] According to the present application, in step (2), the polysiloxane polyurethane polymer Z has the following formula (IV) structure:

[0037]

[0038] According to the present application, in step (3), the mass ratio of the di-thio-acetal bond-containing polyol compound to the diisocyanate in step (2) is 1:(3-25), preferably 1:(3-8).

[0039] According to the present application, in step (3), the reaction temperature is 70-90℃, the reaction time is 30-120min, and the reaction is carried out under stirring.

[0040] According to the present application, preferably, in step (3), the curing method is as follows: standing at room temperature for 4-18h, and then vacuum drying at 60-90℃ for 20-60h.

[0041] A high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing a dynamic dithioacetal bond is prepared by the above method.

[0042] The technical features and beneficial effects of the present application are as follows:

[0043] 1. The present application adopts macromolecular hydroxyethoxypropyl-terminated polydimethylsiloxane as the soft segment, diisocyanate and 1,3-bis(hydroxypropyl)-tetramethyldisiloxane copolymer as the hard segment, and a multi-hydroxyl compound containing a dithioacetal bond as the crosslinking agent to prepare the polysiloxane polyurethane elastomer. The solubility parameter difference between the soft and hard segments of the present application is small, which increases the compatibility of the two phases and avoids macroscopic phase separation. In the case of high hard segment content, the elongation at break of the polysiloxane polyurethane elastomer is improved. The excellent mechanical properties of the elastomer can be obtained without the need to introduce polyester, polyether and other carbon chain macromolecular diols, and the performance advantages of polysiloxane can be fully realized.

[0044] 2. Since traditional physical crosslinking strategies have their limitations, it is difficult to improve the use temperature of silicone-modified polyurethane while ensuring its mechanical properties. Therefore, introducing a dynamic covalent crosslinking strategy on the basis of physical crosslinking is a more suitable choice. The present application uses a multi-hydroxyl compound containing a dynamic dithioacetal bond as a crosslinking agent to introduce a dynamic covalent crosslinking network that can dissociate at high temperatures into the polysiloxane polyurethane polymer to obtain a thermoplastic elastomer, further enhancing the mechanical properties of the elastomer. At the same time, the exchange rate of the dithioacetal bond is low at room temperature, which can maintain the stability of the crosslinking network; at high temperatures, its rapid exchange reaction is activated, and the crosslinking network can respond to external stress through the rapid exchange between dithioacetal bonds, which macroscopically manifests as modulus reduction and thermoplastic behavior. The presence of the dithioacetal crosslinking network enables the elastomer to have a high thermoplasticization temperature and a high use temperature, and can maintain good dimensional stability at high working temperatures and be repeatedly processed.

[0045] 3. The preparation process of the present application is simple, feasible, stable in product performance and good in reproducibility, and is suitable for popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 The nuclear magnetic resonance H spectrum of the crosslinking agent C prepared in Example 1 of the present application;

[0047] Figure 2 The infrared spectrum of the elastomer prepared in Example 1 of the present application;

[0048] Figure 3Thermoplastic temperature test chart of the elastomer prepared for Example 1 of the present application. DETAILED DESCRIPTION

[0049] The technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0050] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all commercially available unless otherwise specified.

[0051] Test description:

[0052] Nuclear magnetic resonance spectrum (NMR) is used to test the sample by AVAVCE (Bruker) 400MHz nuclear magnetic resonance spectrometer, deuterium dimethyl sulfoxide (DMSO-d6) is used as the solvent, and the test is carried out at room temperature.

[0053] Infrared spectrum test is determined by Bruker Tensor 27 type infrared spectrum analyzer. The sample is pressed by potassium bromide, 16 times of sampling, the frequency collection range is from 4000cm -1 to 400cm -1 , and the resolution is 4cm -1 .

[0054] The mechanical property test of the sample is carried out on the Instron 3343 material test system. According to GB / T 1040-2006, the sheet sample obtained by hot pressing the solid sample at 180℃, 15MPa for 15min is cut into dumbbell-shaped sample, the mechanical property of the material is determined by stress-strain analysis, and at least three parallel tests are carried out.

[0055] The thermoplastic temperature test of the sample is carried out by static thermal mechanical analysis (TMA), and the instrument model is TMA4000. The sample is cut into a long strip (20×10×0.5mm), a stress of 1N is applied, the test temperature is 35℃-160℃, and the heating rate is 3℃ / min.

[0056] Each test is carried out at room temperature, normal pressure and relative humidity of 50%, unless otherwise specified.

[0057] Example 1

[0058] A method for preparing a high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing a dynamic dithioacetal bond, comprising the steps of:

[0059] Step 1 Dissolve (8 g, 0.2 mol) sodium hydroxide and (24.4 g, 0.2 mol) p- hydroxybenzaldehyde in a mixture of 40 ml deionized water and 40 ml ethanol in a flask protected by nitrogen atmosphere, then add (18.8 g, 0.1 mol) 1,2-dibromoethane dropwise into the flask. After the dropwise addition, raise the temperature to 75°C and stir for 20 h under nitrogen protection. Then cool the system to 0°C, filter out the needle-like crystals. Wash the filter with ethanol twice to obtain 1,2-bis(4- aldehydephenoxy)ethane.

[0060] Step 2 Dissolve (2.7 g, 0.01 mol) 1,2-bis(4-aldehydephenoxy)ethane and (1.56 g, 0.02 mol) 2-mercaptoethanol in 25 ml tetrahydrofuran in a flask, and add 0.06 g zirconium chloride. Then stir the system at 25°C for 3 h. After the stirring is completed, add 50 ml dichloromethane to the system, and filter out the precipitate. Dissolve the filter in 25 ml tetrahydrofuran again, add 50 ml dichloromethane, filter out the precipitate, and dry to obtain a polyhydroxyl compound containing a dithioacetal bond, denoted as crosslinking agent C.

[0061] Step 3 Add (11.02 g, 42 mmol) dicyclohexylmethane diisocyanate and 30 mL tetrahydrofuran to a flask equipped with a nitrogen inlet tube, a constant pressure dropping funnel, a condenser, and a stirring device at 75°C. Under nitrogen protection and rapid stirring, add a tetrahydrofuran solution of a hydroxyethoxypropyl-terminated polydimethylsiloxane with Mw = 1000 g / mol dropwise from the dropping funnel (wherein the content of the hydroxyethoxypropyl-terminated polydimethylsiloxane is 10.15 g, and the volume of tetrahydrofuran is 30 mL), continue stirring the reaction at 75°C under nitrogen protection for 5 h after the dropwise addition is completed to obtain a solution of isocyanate-terminated prepolymer X.

[0062] Step 4 Disperse (6.51 g, 26 mmol) 1,3-bis(hydroxypropyl)-tetramethyldisiloxane and 0.2 g stannous iso-octoate in 30 mL tetrahydrofuran to obtain solution Y, and transfer it to a dropping funnel. Under nitrogen protection and rapid stirring, add it dropwise to the solution of isocyanate-terminated prepolymer X obtained in step 3, and stir the reaction at 75°C under nitrogen protection for 3 h after the dropwise addition is completed to obtain a solution of polysiloxane polyurethane polymer Z;

[0063] Step 5 Add (1.64 g, 3 mmol) crosslinking agent C to the solution of polysiloxane polyurethane polymer Z, and continue stirring the reaction at 75°C for 1 h before ending. Transfer the product to a polytetrafluoroethylene mold, and place it at room temperature for 5 h to allow the solvent to evaporate, and then place it in a vacuum oven at 80°C for 24 h to dry to obtain a high-strength high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing a dynamic dithioacetal bond.

[0064] The nuclear magnetic resonance H spectrum of the crosslinking agent C obtained in this example in deuterated dimethyl sulfoxide is shown in Figure 1, which proves that the target product is successfully prepared. Figure 1

[0065] The FTIR spectrum of the high-strength high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds obtained in this example is shown in Figure 2, which is at 2270 cm Figure 2 -1 The disappearance of the stretching vibration peak of N=C=O indicates that the NCO reaction is complete; the absorption peak near 3310-3350 cm-1 is the stretching vibration peak of the carbamate N-H, and the absorption peak at 1700-1735 cm -1 The stretching vibration peak of the carbonyl C=O. The FTIR spectrum proves that the target product is successfully prepared.

[0066] The high-strength high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds obtained in this example has a tensile strength of 22.4 MPa and an elongation at break of 673%.

[0067] The high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds obtained in this example has a thermoplastic temperature of 124°C, which has a relatively high thermoplastic temperature. Figure 3

[0068] Example 2

[0069] A method for preparing a high-strength high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds, comprising the steps of:

[0070] Steps 1 and 2 are the same as steps 1 and 2 of Example 1.

[0071] Step 3: Add (13.01 g, 52 mmol) diphenylmethane diisocyanate and 30 mL tetrahydrofuran to a flask equipped with a nitrogen inlet tube, constant pressure dropping funnel, condenser, stirring device at 75°C. Under nitrogen, rapidly stir and add dropwise a tetrahydrofuran solution of Mw=1000 g / mol hydroxyethoxypropyl-terminated polydimethylsiloxane (wherein the content of hydroxyethoxypropyl-terminated polydimethylsiloxane is 10.12 g and the volume of tetrahydrofuran is 30 mL) from the dropping funnel. After the end of the dropwise addition, continue stirring under nitrogen protection at 75°C for 5 h to obtain a solution of isocyanate-terminated prepolymer X.

[0072] ​​​Step 4 To a solution Y of (9.01 g, 36 mmol) 1,3-bis(hydroxypropyl)- tetramethyldisiloxane, 0.2 g stannous octoate in 30 mL tetrahydrofuran was added dropwise into a solution of isocyanate-terminated prepolymer X from Step 3 in a dropping funnel under nitrogen, fast stirring, after the addition was completed, the solution of polysiloxane polyurethane polymer Z was stirred at 75 °C for 3 h under nitrogen.

[0073] Step 5 To the solution of polysiloxane polyurethane polymer Z, (1.64 g, 3 mmol) crosslinker C was added, after the solution was stirred at 75 °C for 1 h, the reaction was completed. The product was transferred into a polytetrafluoroethylene mold, and placed at room temperature for 5 h to allow the solvent to evaporate, then placed in a vacuum oven at 80 °C for 24 h to dry, to obtain a high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds.

[0074] The high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds obtained in this example had a tensile strength of 21.2 MPa and an elongation at break of 565%.

[0075] The high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds obtained in this example had a thermoplastic temperature of 125 °C.

[0076] Example 3

[0077] A method for preparing a high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds, comprising the steps of:

[0078] Step 1, 2 were the same as Step 1, 2 of Example 1.

[0079] Step 3 To a flask equipped with a nitrogen inlet tube, a constant pressure dropping funnel, a condenser tube, and a stirring device, (8.40 g, 32 mmol) dicyclohexylmethane diisocyanate and 30 mL tetrahydrofuran were added at 75 °C. Nitrogen was bubbled, and a tetrahydrofuran solution of hydroxyethoxypropyl-terminated polydimethylsiloxane with Mw = 1000 g / mol (wherein the content of hydroxyethoxypropyl-terminated polydimethylsiloxane was 10.12 g, and the volume of tetrahydrofuran was 30 mL) was added dropwise from the dropping funnel. After the addition was completed, the solution was stirred at 75 °C under nitrogen for 5 h to obtain a solution of isocyanate-terminated prepolymer X.

[0080] Step 4 To a solution Y of (4.51 g, 18 mmol) 1,3-bis(hydroxypropyl)- tetramethyldisiloxane, 0.2 g stannous octoate was thoroughly dispersed in 30 mL tetrahydrofuran and transferred to a dropping funnel, under nitrogen, fast stirring, the solution was added dropwise to the solution of isocyanate-terminated prepolymer X from Step 3, after the addition was completed, the solution of polysiloxane polyurethane polymer Z was obtained by stirring at 75 °C for 3 h under nitrogen.

[0081] Step 5 To the solution of polysiloxane polyurethane polymer Z, (1.09 g, 2 mmol) crosslinker C was added, after stirring at 75 °C for 1 h, the reaction was completed. The product was transferred to a polytetrafluoroethylene mold, and placed at room temperature for 5 h to allow the solvent to evaporate, then placed in a vacuum oven at 80 °C for 24 h to dry, to obtain a high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds.

[0082] The high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds obtained in this example had a tensile strength of 18 MPa and an elongation at break of 698%.

[0083] The high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds obtained in this example had a thermoplastic temperature of 125 °C.

[0084] Example 4

[0085] A method for preparing a high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds, comprising the steps of:

[0086] Step 1, 2 were the same as Step 1, 2 of Example 1.

[0087] Step 3 To a flask equipped with a nitrogen inlet tube, a constant pressure dropping funnel, a condenser, and a stirring device, (11.02 g, 42 mmol) dicyclohexylmethane diisocyanate and 30 mL tetrahydrofuran were added at 75 °C. Under nitrogen, fast stirring, a tetrahydrofuran solution of hydroxyethoxypropyl-terminated polydimethylsiloxane with Mw = 1000 g / mol (wherein the content of hydroxyethoxypropyl-terminated polydimethylsiloxane was 10.12 g and the volume of tetrahydrofuran was 30 mL) was added dropwise from the dropping funnel, after the addition was completed, the solution was stirred at 75 °C under nitrogen for 5 h to obtain an isocyanate-terminated prepolymer X solution.

[0088] Step 4 To solution Y, which was prepared by dispersing (5.01 g, 20 mmol) 1,3-bis(hydroxypropyl)-tetramethyldisiloxane, 0.2 g stannous iso-octoate in 30 mL tetrahydrofuran, was added dropwise to the solution of isocyanate-terminated prepolymer X from Step 3 under nitrogen, rapid stirring, and the addition was completed. The reaction was continued at 75 °C for 3 h to give a solution of polysiloxane polyurethane polymer Z.

[0089] Step 5 To the solution of polysiloxane polyurethane polymer Z, (3.28 g, 6 mmol) crosslinker C was added, and the reaction was continued at 75 °C for 1 h. The product was transferred to a Teflon mold, and the solvent was allowed to evaporate at room temperature for 5 h. The product was then dried in a vacuum oven at 80 °C for 24 h to give a high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal linkages.

[0090] The high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal linkages obtained in this example had a tensile strength of 14.7 MPa and an elongation at break of 325%.

[0091] The high-strength high-thermoplastic temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal linkages obtained in this example had a thermoplastic temperature of 129 °C.

[0092] Comparative Example 1

[0093] A method for preparing a polysiloxane polyurethane elastomer, which differs from Example 1 in that in Step 4, 1,3-bis(hydroxypropyl)-tetramethyldisiloxane was replaced by equimolar amount of 1,4-butanediol, and the other raw materials, amounts, parameters, and steps were the same as in Example 1.

[0094] The elastomer obtained in this comparative example had a tensile strength of 7.2 MPa and an elongation at break of 137%.

[0095] The elastomer obtained in this comparative example had a thermoplastic temperature of 116 °C.

[0096] This comparative example differs from Example 1 in that no siloxane-silicon chain segment was added to the hard segment component, resulting in a large difference in solubility parameter between the soft and hard segments. The product was severely phase-separated, and had poor mechanical properties.

[0097] Comparative Example 2

[0098] A method for preparing a polysiloxane polyurethane elastomer, which differs from Example 1 in that in Step 5, no crosslinker C was added, and the product from Step 4 was directly transferred to a Teflon mold, and the solvent was allowed to evaporate at room temperature for 5 h. The product was then dried in a vacuum oven at 80 °C for 24 h. The other raw materials, amounts, parameters, and steps were the same as in Example 1.

[0099] The tensile strength of the elastomer obtained in this comparative example was 18.1 MPa and the elongation at break was 657%.

[0100] The thermoplastic temperature of the elastomer obtained in this comparative example was 96°C.

[0101] The difference between this comparative example and Example 1 is that no dynamic dithioacetal crosslinking agent was used and the material obtained was crosslinked entirely by physical action. There was a marked decrease in mechanical strength and thermoplastic temperature compared with Example 1.

Claims

1. A method for preparing a high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds, comprising the following steps: (1) In a mixed solvent of anhydrous ethanol and water, in the presence of sodium hydroxide, 1,2-dibromoethane and p-hydroxybenzaldehyde react to give 1,2-bis(4-aldehyde phenoxy)ethane; in tetrahydrofuran, in the presence of zirconium chloride, 1,2-bis(4-aldehyde phenoxy)ethane reacts with 2-mercaptoethanol to give a polyhydroxy compound containing a dithioacetal bond; the polyhydroxy compound containing the dithioacetal bond has the structure shown in formula (I): （Ⅰ） (2) In solvent A, diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane are reacted to obtain a solution of isocyanate-terminated prepolymer X; 1,3-bis(hydroxypropyl)-tetramethyldisiloxane and stannous isooctanoate are fully dispersed in solvent B to obtain solution Y; the solution of isocyanate-terminated prepolymer X is mixed with solution Y and reacted to obtain a solution of polysiloxane polyurethane polymer Z; (3) Mix a solution of a polyhydroxy compound containing dithioacetal bonds and a polysiloxane polyurethane polymer Z, react and cure to obtain a high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds.

2. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that, Step (1) includes one or more of the following conditions: i. The molar ratio of 1,2-dibromoethane and p-hydroxybenzaldehyde is 1:(2~2.3); the volume ratio of water to anhydrous ethanol is 1:(0.6~4); the mass ratio of p-hydroxybenzaldehyde to the volume ratio of the mixed solvent is 1g:(3~8)ml; the molar ratio of p-hydroxybenzaldehyde to sodium hydroxide is 1:(1~1.2); ii. 1,2-Dibromoethane is added dropwise to the reaction system; iii. The reaction temperature of 1,2-dibromoethane and p-hydroxybenzaldehyde is 55~85℃, and the reaction time is 16~24h. The reaction is carried out under the protection of a protective gas and under stirring conditions; the protective gas is nitrogen or argon.

3. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that, Step (1) includes one or more of the following conditions: i. The molar ratio of 1,2-bis(4-aldehyde phenoxy)ethane to 2-mercaptoethanol is 1:(2~2.3), the mass ratio of 1,2-bis(4-aldehyde phenoxy)ethane to the volume ratio of tetrahydrofuran is 1g:(5~20)ml, and the mass ratio of 1,2-bis(4-aldehyde phenoxy)ethane to zirconium chloride is 1:(0.01~0.05). ii. The reaction temperature of 1,2-bis(4-aldehyde phenoxy)ethane with 2-mercaptoethanol is 15~60℃, the reaction time is 2~8h, and the reaction is carried out under stirring conditions.

4. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that, Step (2) includes one or more of the following conditions: i. Solvent A is selected from one of toluene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, methyl isobutyl ketone, γ-butyrolactone, dimethyl sulfoxide, acetonitrile, dioxane, xylene, isopropanol, dichloromethane, acetone, ethyl acetate, or n-hexane; the total mass ratio of diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane to the volume ratio of solvent A is 1 g : 0.5~30 ml; ii. The diisocyanate is one or a combination of two or more of toluene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, methylcyclohexyl diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, terephthalic diisocyanate, terephthalic diisocyanate or tetramethyl terephthalic diisocyanate; iii. The molar ratio of diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane is (1~13):1; iv. The weight-average molecular weight of hydroxyethoxypropyl-terminated polydimethylsiloxane is 500~5000 g / mol.

5. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 4, characterized in that, Includes one or more of the following conditions: i. The total mass ratio of diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane to solvent A is 1 g : 0.5~18 ml; ii. The molar ratio of diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane is (3.1~5.2):

1.

6. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that, Step (2) includes one or more of the following conditions: i. The hydroxyethoxypropyl-terminated polydimethylsiloxane is added dropwise to the reaction system as a solution of hydroxyethoxypropyl-terminated polydimethylsiloxane under stirring and protective gas conditions; the type of solvent used for the hydroxyethoxypropyl-terminated polydimethylsiloxane solution is the same as that used for solvent A, and the concentration of the hydroxyethoxypropyl-terminated polydimethylsiloxane solution is 0.1~0.5 g / mL; the protective gas is nitrogen or argon. ii. The reaction temperature of diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane is 50~100℃, the reaction time is 30~600min, and the reaction is carried out under stirring and protective gas protection; the protective gas is nitrogen or argon.

7. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 6, characterized in that, The reaction temperature of diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane is 70~90℃, and the reaction time is 100~360min.

8. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that, In step (2), the method for preparing the solution of isocyanate-terminated prepolymer X includes the following steps: mixing diisocyanate and solvent A1, and adding dropwise a mixture of hydroxyethoxypropyl-terminated polydimethylsiloxane and solvent A2 under stirring conditions and protective gas protection, and obtaining the solution of isocyanate-terminated prepolymer X by reaction; the types of solvent A1 and solvent A2 are the same as those of solvent A, and the total volume of solvent A1 and solvent A2 is the same as that of solvent A.

9. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that, Step (2) includes one or more of the following conditions: i. Solvent B is selected from one of toluene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, methyl isobutyl ketone, γ-butyrolactone, dimethyl sulfoxide, acetonitrile, dioxane, xylene, isopropanol, dichloromethane, acetone, ethyl acetate, or n-hexane; the mass ratio of 1,3-bis(hydroxypropyl)-tetramethyldisiloxane to the volume ratio of solvent B is 1 g: 2~15 ml; ii. The mass ratio of 1,3-bis(hydroxypropyl)-tetramethyldisiloxane to stannous isooctanoate is 100:(0.05~5); iii. The molar ratio of diisocyanate and 1,3-bis(hydroxypropyl)-tetramethyldisiloxane is 1:(0.3~1).

10. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 9, characterized in that, Includes one or more of the following conditions: i. The mass ratio of 1,3-bis(hydroxypropyl)-tetramethyldisiloxane to the volume ratio of solvent B is 1g : 2~10ml; ii. The mass ratio of 1,3-bis(hydroxypropyl)-tetramethyldisiloxane to stannous isooctanoate is 100:(2~4.4). iii. The molar ratio of diisocyanate and 1,3-bis(hydroxypropyl)-tetramethyldisiloxane is 1:(0.47~0.7).

11. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that, Step (2) includes one or more of the following conditions: i. Solution Y is added dropwise to the solution of isocyanate-terminated prepolymer X under protective gas and stirring conditions; the protective gas is nitrogen or argon. ii. The reaction temperature of the solution of isocyanate-terminated prepolymer X with solution Y is 50~100℃, the reaction time is 30~480min, and the reaction is carried out under stirring and protective gas protection; the protective gas is nitrogen or argon.

12. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 11, characterized in that, The reaction temperature of the solution of isocyanate-terminated prepolymer X with solution Y is 70~90℃, and the reaction time is 30~240min.

13. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that, Step (3) includes one or more of the following conditions: i. The mass ratio of the polyhydroxy compound containing a dithioacetal bond to the diisocyanate in step (2) is 1:(3~25); ii. The reaction temperature is 70~90℃, the reaction time is 30~120min, and the reaction is carried out under stirring conditions; iii. The curing method is as follows: let stand at room temperature for 4~18 hours, then vacuum dry at 60~90℃ for 20~60 hours.

14. The method for preparing the high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 13, characterized in that, The mass ratio of the polyhydroxy compound containing a dithioacetal bond to the diisocyanate in step (2) is 1:(3~8).

15. A high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds, prepared by the method described in any one of claims 1-14.

Images