Dynamic dithioacetal bond-containing polysiloxane polyurethane thermoplastic elastomer with high strength and high thermal plastic temperature and preparation method of dynamic dithioacetal bond-containing polysiloxane polyurethane thermoplastic elastomer

Abstract

The invention provides a dynamic dithioacetal bond-containing polysiloxane polyurethane thermoplastic elastomer with high strength and high thermal plastic temperature and a preparation method of the dynamic dithioacetal bond-containing polysiloxane polyurethane thermoplastic elastomer. According to the invention, macromolecular polydimethylsiloxane is used as a soft segment, the diisocyanate and 1, 3-bis (hydroxypropyl)-tetramethyldisiloxane copolymer is used as a hard segment, and the polyhydroxy compound containing dynamic dithioacetal bonds is used as a cross-linking agent, so that the prepared elastomer has good mechanical properties and high thermoplastic temperature, and can be repeatedly processed; the preparation process is simple and feasible, and the product has stable performance and good reproducibility and is suitable for popularization and application.

Description

Technical Field

[0001] The invention relates to a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing a dynamic dithioacetal bond and a preparation method thereof, belonging to the technical field of polymer material synthesis. Background Art

[0002] Polyurethane elastomer is a kind of elastic polymer material containing more carbamate units in the molecular chain. It is usually made by polymerization reaction of oligomer polyols, polyisocyanates, chain extenders, and crosslinkers as raw materials. It has high elasticity and strength, outstanding wear resistance, and good resistance to oil, chemicals, and impact. Among them, thermoplastic polyurethane elastomer (TPU) is a block linear polymer, with a short-chain oligomer diol as the soft segment, and a dense carbamate structure formed by diisocyanate and diol chain extender as the hard segment. There are only physical crosslinks or slight chemical crosslinks between the molecular chains. This crosslinking method is reversible, and the intermolecular effect is weakened during thermal processing, and the modulus is reduced, thereby giving the material the properties of thermoplastic molding, making it suitable for the same large-scale processing equipment and processes as thermoplastics. Thanks to its excellent comprehensive performance and green and environmentally friendly processing and molding methods, thermoplastic polyurethane elastomers are widely used in many fields such as automobiles, cables, clothing, films and tubes, and wires. But at the same time, traditional thermoplastic polyurethane elastomers have some shortcomings that limit their application, such as containing toxic odor small molecules, poor surface properties, poor weather resistance and yellowing resistance, general high temperature resistance, and the use temperature generally does not exceed 120°C. In order to overcome these shortcomings, people try to introduce polysiloxanes with ideal weather resistance, high and low temperature resistance, chemical inertness and low surface tension into the molecular chain of thermoplastic polyurethane by block polymerization to improve its performance. This type of material is also called polysiloxane polyurethane thermoplastic elastomer.

[0003] In the above polysiloxane-modified polyurethane elastomer, the polysiloxane segment of the soft segment and the polyurethane of the hard segment will each form an independent micro-region, wherein the soft segment micro-region provides flexibility and elasticity for the material, while the hard segment micro-region, as a physical cross-linking point, provides strength and hardness for the material, and its phase transition temperature directly affects the thermoplasticization temperature of the material. Due to the huge solubility parameter difference between the polysiloxane segment and the polyurethane, the compatibility of the soft and hard micro-regions is poor, and they tend to further repel and form macroscopic phase separation, so that the mechanical properties of the organosilicon-modified polyurethane with polysiloxane as the soft segment are generally low, and it is difficult to give full play to the performance advantages of the polyurethane material. 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 introducing polylactic acid polyol and polysiloxane into polyurethane at the same time; patent CN118930873A reacts carboxyl-terminated polybutadiene with polysiloxane diol, and then uses the obtained block copolymer as a macromolecular diol to prepare a polyurethane elastomer with good low-temperature resilience and aging resistance; patent CN114891184A uses polytetrahydrofuran diol and hydroxyl-terminated polysiloxane as mixed soft segments, and adds flame retardants to prepare silicone polyurethane with flame retardant properties. However, this method requires the addition of a large amount of carbon chain macromolecular diols, which often exceeds 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 pay attention to the thermoplasticization 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. The document "Eur. Polym. J., 198 (2023), 112416" uses bis (hydroxyethyl sulfide ethyl) -tetramethyl disiloxane and 4,4'-methylene diphenyl diisocyanate (MDI) 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, this type of material is restricted by the structure of the hard segment, and it is difficult to form tightly and regularly arranged hard segment micro-regions, and it is difficult to increase the thermoplasticization temperature.

[0004] With the increasing requirements for material performance in industrial production and social development, it is urgent to develop a silicone polyurethane thermoplastic elastomer with excellent mechanical properties, high operating temperature and repeatable processing. This requires that the material can maintain good dimensional stability at a higher operating temperature, that is, it has a high plasticizing temperature. Summary of the invention

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

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds, comprising the steps of:

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

[0009] (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 to obtain a solution of polysiloxane polyurethane polymer Z through reaction;

[0010] (3) Mixing a solution of a polyhydroxy compound containing a dithioacetal bond and a polysiloxane polyurethane polymer Z, reacting, and curing to obtain a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing a dynamic dithioacetal bond.

[0011] Preferably, 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 volume ratio of the mixed solvent is 1 g:(3-8) ml; and the molar ratio of p-hydroxybenzaldehyde to sodium hydroxide is 1:(1-1.2).

[0012] Preferably according to the present invention, in step (1), 1,2-dibromoethane is added dropwise into the reaction system.

[0013] According to the preferred embodiment of the present invention, in step (1), the reaction temperature of 1,2-dibromoethane and p-hydroxybenzaldehyde is 55-85°C, the reaction time is 16-24h, and the reaction is carried out under the protection of protective gas and stirring. The protective gas is nitrogen or argon.

[0014] Preferably, in step (1), the post-treatment method of the reaction solution obtained by the reaction of 1,2-dibromoethane and p-hydroxybenzaldehyde is as follows: the reaction solution is cooled to 0°C, the precipitate is filtered out, and the precipitate is washed with ethanol to obtain 1,2-bis(4-formylphenoxy)ethane.

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

[0016] Preferably, in step (1), the reaction temperature of 1,2-bis(4-formylphenoxy)ethane and 2-mercaptoethanol is 15-60° C., the reaction time is 2-8 h, and the reaction is carried out under stirring conditions.

[0017] Preferably, in step (1), the post-treatment method of the reaction solution obtained by the reaction of 1,2-bis(4-formylphenoxy)ethane and 2-mercaptoethanol is as follows: adding dichloromethane to the reaction solution to precipitate, filtering the precipitate; dissolving the precipitate in tetrahydrofuran, adding dichloromethane, filtering the precipitate, and drying to obtain a polyhydroxy compound containing a dithioacetal bond.

[0018] Preferably, according to the present invention, in step (1), the polyhydroxy compound containing dithioacetal bonds (crosslinking agent C) has a structure shown in formula (I):

[0019]

[0020] According to the preferred embodiment of the present invention, in step (2), solvent A is selected from 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 volume ratio of the total mass of diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane to solvent A is 1g:0.5-30ml, preferably 1g:0.5-18ml.

[0021] Preferably according to the present invention, in step (2), the diisocyanate is 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, or a combination of two or more thereof.

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

[0023] Preferably according to the present invention, in step (2), the weight average molecular weight of the hydroxyethoxypropyl terminated polydimethylsiloxane is 500 to 5000 g / mol.

[0024] According to the present invention, in step (2), the hydroxyethoxypropyl terminated polydimethylsiloxane has a structure as shown in the following formula (II):

[0025]

[0026] 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 protective gas protection; the type of solvent used for the hydroxyethoxypropyl-terminated polydimethylsiloxane solution is the same as solvent A, and the concentration of the hydroxyethoxypropyl-terminated polydimethylsiloxane solution is 0.1-0.5 g / mL; and the protective gas is nitrogen or argon.

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

[0028] Preferably, in step (2) of the present invention, the method for preparing a solution of an isocyanate-terminated prepolymer X comprises the steps of: mixing a diisocyanate and a solvent A1, and dropwise adding a mixed solution of a hydroxyethoxypropyl-terminated polydimethylsiloxane and a solvent A2 under stirring and protective gas protection, to obtain a solution of an isocyanate-terminated prepolymer X through reaction; preferably, the types of solvent A1 and solvent A2 are the same as solvent A, and the total volume of solvent A1 and solvent A2 is the same as solvent A.

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

[0030]

[0031] According to the preferred embodiment of the present invention, in step (2), solvent B is selected from 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 1g:2-15ml, preferably 1g:2-10ml.

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

[0033] Preferably according to the present invention, 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] Preferably, in step (2), the solution Y is added dropwise into the solution of the isocyanate-terminated prepolymer X under protection of a protective gas and stirring. Preferably, the protective gas is nitrogen or argon.

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

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

[0037]

[0038] Preferably according to the present invention, in step (3), the mass ratio of the polyhydroxy compound containing a dithioacetal bond to the diisocyanate in step (2) is 1:(3-25), preferably 1:(3-8).

[0039] Preferably according to the present invention, in step (3), the reaction temperature is 70-90° C., the reaction time is 30-120 min, and the reaction is carried out under stirring conditions.

[0040] Preferably, according to the present invention, in step (3), the curing method is as follows: standing at room temperature for 4 to 18 hours, and then vacuum drying at 60 to 90° C. for 20 to 60 hours.

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

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

[0043] 1. The present invention adopts a macromolecular hydroxyethoxypropyl-terminated polydimethylsiloxane as a soft segment, a copolymer of diisocyanate and 1,3-bis(hydroxypropyl)-tetramethyldisiloxane as a hard segment, and a polyhydroxy compound containing a dithioacetal bond as a crosslinking agent to prepare a polysiloxane polyurethane elastomer. The difference in solubility parameters between the soft and hard segments of the elastomer of the present invention is small, which increases the compatibility of the two phases, avoids macroscopic phase separation, and improves the elongation at break of the polysiloxane polyurethane elastomer under the condition of high hard segment content. An elastomer with excellent mechanical properties can be obtained without the introduction of carbon chain macromolecular diols such as polyesters and polyethers, which can fully reflect the performance advantages of polysiloxane.

[0044] 2. Due to the limitations of the traditional physical crosslinking strategy, it is difficult to increase the operating temperature while ensuring the mechanical properties of the organosilicon-modified polyurethane. Therefore, introducing a dynamic covalent crosslinking strategy based on physical crosslinking is a more appropriate choice. The present invention uses a polyhydroxy compound containing a dynamic dithioacetal bond as a crosslinking agent, and introduces a dynamic covalent crosslinking network that can be dissociated at high temperature into a polysiloxane polyurethane polymer to obtain a thermoplastic elastomer, which further enhances the mechanical properties of the elastomer. At the same time, the exchange rate of the dithioacetal bond is low at room temperature, which can keep the crosslinking network stable; at high temperatures, its rapid exchange reaction is activated, and the crosslinking network can respond to external stress through the rapid exchange between the dithioacetal bonds, which is manifested as a decrease in modulus and thermoplastic behavior in the macroscopic sense. The presence of the dithioacetal crosslinking network enables the elastomer to have a high thermoplasticization temperature, a high operating temperature, and can maintain good dimensional stability at a higher operating temperature, and can be processed repeatedly.

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

[0046] Figure 1 This is the H NMR spectrum of the cross-linking agent C prepared in Example 1 of the present invention;

[0047] Figure 2 This is an infrared spectrum of the elastomer prepared in Example 1 of the present invention;

[0048] Figure 3This is a thermoplastic temperature test chart of the elastomer prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

[0051] Test description:

[0052] Nuclear magnetic resonance spectroscopy (NMR) was performed using an AVAVCE (Bruker) 400 MHz NMR spectrometer to test the samples, using deuterated dimethyl sulfoxide (DMSO-d6) as the solvent, and the test was performed at room temperature.

[0053] The infrared spectrum test was carried out by Bruker Tensor 27 infrared spectrometer. The sample was pressed into potassium bromide tablets and sampled 16 times. The frequency collection range was from 4000 cm -1 Up to 400cm -1 , resolution 4cm -1 .

[0054] The mechanical properties test of the samples was conducted on an Instron 3343 material testing system. According to GB / T 1040-2006, the thin slices obtained by hot pressing the solid samples at 180°C and 15MPa for 15 minutes were cut into dumbbell-shaped specimens, and the mechanical properties of the materials were determined by stress-strain analysis, and at least three parallel tests were performed.

[0055] The thermoplastic temperature test of the sample was conducted by static thermomechanical analysis (TMA) using the Netzsch TMA4000. The sample was cut into strips (20×10×0.5mm), a stress of 1N was applied, the test temperature was 35℃~160℃, and the heating rate was 3℃ / min.

[0056] All tests were conducted at normal temperature, normal pressure and a relative humidity of 50%, unless otherwise stated.

[0057] Example 1

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

[0059] Step 1: In a three-necked flask protected by nitrogen atmosphere, (8g, 0.2mol) sodium hydroxide and (24.4g, 0.2mol) p-hydroxybenzaldehyde are dissolved in a mixed solution of 40ml deionized water and 40ml ethanol, and then (18.8g, 0.1mol) 1,2-dibromoethane is added dropwise to the reaction flask. After the dropwise addition, the temperature is raised to 75°C and stirred for 20h under nitrogen protection. The system is then cooled to 0°C and the needle-shaped crystals are filtered out. The filtrate is rinsed twice with ethanol to obtain 1,2-bis(4-formylphenoxy)ethane.

[0060] Step 2: Dissolve (2.7 g, 0.01 mol) 1,2-bis(4-formylphenoxy)ethane and (1.56 g, 0.02 mol) 2-mercaptoethanol in 25 ml tetrahydrofuran in a three-necked flask, and add 0.06 g zirconium chloride. Then stir the system at 25 °C for 3 h. After stirring, add 50 ml of dichloromethane to the system and filter out the precipitate. Dissolve the filtrate again in 25 ml tetrahydrofuran, add 50 ml of dichloromethane, filter out the precipitate, and dry it to obtain a polyhydroxy compound containing a dithioacetal bond, which is recorded as crosslinker C.

[0061] Step 3: Add (11.02 g, 42 mmol) of dicyclohexylmethane diisocyanate and 30 mL of tetrahydrofuran to a flask equipped with a nitrogen conduit, a constant pressure dropping funnel, a condenser and a stirring device at 75°C. Nitrogen is passed through and stirred rapidly, and a tetrahydrofuran solution of a hydroxyethoxypropyl-terminated polydimethylsiloxane of Mw=1000 g / mol (wherein, the content of the hydroxyethoxypropyl-terminated polydimethylsiloxane is 10.15 g and the volume of tetrahydrofuran is 30 mL) is added dropwise from the dropping funnel. After the addition is completed, the reaction is continued under stirring at 75°C for 5 h under nitrogen protection to obtain a solution of an isocyanate-terminated prepolymer X.

[0062] Step 4: Disperse (6.51 g, 26 mmol) of 1,3-bis(hydroxypropyl)-tetramethyldisiloxane and 0.2 g of stannous isooctanoate in 30 mL of tetrahydrofuran to obtain a solution Y, and transfer the solution to a dropping funnel. Pass nitrogen gas and stir rapidly, and add the solution dropwise to the isocyanate-terminated prepolymer X obtained in step 3. After the addition is complete, stir and react at 75° C. under nitrogen protection for 3 h to obtain a solution of a polysiloxane polyurethane polymer Z.

[0063] Step 5: Add (1.64 g, 3 mmol) of crosslinker C to the solution of polysiloxane polyurethane polymer Z, continue stirring at 75°C for 1 hour, and then end. The product is transferred to a polytetrafluoroethylene mold, placed at room temperature for 5 hours to allow the solvent to evaporate, and then placed in a vacuum oven at 80°C for 24 hours to obtain a high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds.

[0064] The H NMR spectrum of the cross-linking agent C obtained in this example in deuterated dimethyl sulfoxide is as follows: Figure 1 As shown, it is proved that the target product was successfully prepared.

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

[0066] The high-strength and 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 thermoplastic temperature of the high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds obtained in this embodiment is as follows: Figure 3 , which is 124°C and has a higher thermoplastic temperature.

[0068] Example 2

[0069] A method for preparing a high-strength and 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) of diphenylmethane diisocyanate and 30 mL of tetrahydrofuran to a flask equipped with a nitrogen conduit, a constant pressure dropping funnel, a condenser and a stirring device at 75°C. Nitrogen is passed through and stirred rapidly, and a tetrahydrofuran solution of a hydroxyethoxypropyl-terminated polydimethylsiloxane of Mw=1000 g / mol (wherein, the content of the hydroxyethoxypropyl-terminated polydimethylsiloxane is 10.12 g and the volume of tetrahydrofuran is 30 mL) is added dropwise from the dropping funnel. After the addition is completed, the reaction is continued under stirring at 75°C under nitrogen protection for 5 h to obtain a solution of an isocyanate-terminated prepolymer X.

[0072] Step 4: (9.01 g, 36 mmol) 1,3-bis(hydroxypropyl)-tetramethyldisiloxane and 0.2 g stannous isooctanoate are fully dispersed in 30 mL tetrahydrofuran to obtain a solution Y, and the solution Y is transferred to a dropping funnel, and nitrogen is passed through and rapidly stirred, and the solution is added dropwise to the isocyanate-terminated prepolymer X obtained in step 3. After the dropwise addition is completed, the reaction is stirred at 75° C. under nitrogen protection for 3 h to obtain a solution of a polysiloxane polyurethane polymer Z;

[0073] Step 5: Add (1.64 g, 3 mmol) of crosslinker C to the solution of polysiloxane polyurethane polymer Z, continue stirring at 75°C for 1 hour, and then end. The product is transferred to a polytetrafluoroethylene mold, placed at room temperature for 5 hours to allow the solvent to evaporate, and then placed in a vacuum oven at 80°C for 24 hours to obtain a high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds.

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

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

[0076] Example 3

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

[0078] Steps 1 and 2 are the same as steps 1 and 2 of Example 1.

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

[0080] Step 4: (4.51 g, 18 mmol) 1,3-bis(hydroxypropyl)-tetramethyldisiloxane and 0.2 g stannous isooctanoate are fully dispersed in 30 mL tetrahydrofuran to obtain a solution Y, and the solution Y is transferred to a dropping funnel, and nitrogen is passed through and rapidly stirred, and the solution is added dropwise to the isocyanate-terminated prepolymer X obtained in step 3. After the dropwise addition is completed, the reaction is stirred at 75° C. under nitrogen protection for 3 h to obtain a solution of a polysiloxane polyurethane polymer Z;

[0081] Step 5: Add (1.09 g, 2 mmol) of crosslinker C to the solution of polysiloxane polyurethane polymer Z, continue stirring at 75°C for 1 hour, and then end. The product is transferred to a polytetrafluoroethylene mold, placed at room temperature for 5 hours to allow the solvent to evaporate, and then placed in a vacuum oven at 80°C for 24 hours to obtain a high-strength, high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds.

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

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

[0084] Example 4

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

[0086] Steps 1 and 2 are the same as steps 1 and 2 of Example 1.

[0087] Step 3: Add (11.02 g, 42 mmol) of dicyclohexylmethane diisocyanate and 30 mL of tetrahydrofuran to a flask equipped with a nitrogen conduit, a constant pressure dropping funnel, a condenser and a stirring device at 75°C. Nitrogen is passed through and stirred rapidly, and 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) is added dropwise from the dropping funnel. After the addition is completed, the reaction is continued under stirring at 75°C under nitrogen protection for 5 h to obtain a solution of isocyanate-terminated prepolymer X.

[0088] Step 4: (5.01 g, 20 mmol) 1,3-bis(hydroxypropyl)-tetramethyldisiloxane and 0.2 g stannous isooctanoate are fully dispersed in 30 mL tetrahydrofuran to obtain a solution Y, and the solution Y is transferred to a dropping funnel, and nitrogen is passed through and rapidly stirred, and the solution is added dropwise to the isocyanate-terminated prepolymer X obtained in step 3. After the dropwise addition is completed, the reaction is stirred at 75° C. under nitrogen protection for 3 h to obtain a solution of a polysiloxane polyurethane polymer Z;

[0089] Step 5: Add (3.28 g, 6 mmol) of crosslinker C to the solution of polysiloxane polyurethane polymer Z, continue stirring at 75°C for 1 hour, and then end. The product is transferred to a polytetrafluoroethylene mold, placed at room temperature for 5 hours to allow the solvent to evaporate, and then placed in a vacuum oven at 80°C for 24 hours to obtain a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds.

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

[0091] The high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds obtained in this example has 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 is replaced by an equal molar amount of 1,4-butanediol, and the remaining raw materials, amounts, parameters and steps are the same as those in Example 1.

[0094] The tensile strength of the elastomer obtained in this comparative example is 7.2 MPa, and the elongation at break is 137%.

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

[0096] The difference between this comparative example and Example 1 is that no silicon-oxygen-silicon chain is added to the hard segment component, resulting in a large difference in solubility parameters between the soft and hard segments. The product has severe phase separation and 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 crosslinking agent C is added, but the product in step 4 is directly transferred to a polytetrafluoroethylene mold, placed at room temperature for 5 hours to allow the solvent to evaporate, and then placed in a vacuum oven at 80° C. for drying for 24 hours. The remaining raw materials, amounts, parameters and steps are the same as those in Example 1.

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

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

[0101] The difference between this comparative example and Example 1 is that no dynamic dithioacetal bond crosslinking agent is used, and the obtained material is completely crosslinked by physical action. Compared with Example 1, the mechanical strength and thermoplastic temperature are significantly reduced.

Claims

1. A method for preparing a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds, comprising the steps of: (1) In a mixed solvent of anhydrous ethanol and water, in the presence of sodium hydroxide, 1,2-dibromoethane and p-hydroxybenzaldehyde are reacted to obtain 1,2-bis(4-formylphenoxy)ethane; in tetrahydrofuran, in the presence of zirconium chloride, 1,2-bis(4-formylphenoxy)ethane and 2-mercaptoethanol are reacted to obtain a polyhydroxy compound containing a dithioacetal bond; (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 to obtain a solution of polysiloxane polyurethane polymer Z through reaction; (3) Mixing a solution of a polyhydroxy compound containing a dithioacetal bond and a polysiloxane polyurethane polymer Z, reacting, and curing to obtain a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing a dynamic dithioacetal bond.

2. The method for preparing a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that: In step (1), one or more of the following conditions are included: i. 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 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 into the reaction system; iii. The reaction temperature of 1,2-dibromoethane and p-hydroxybenzaldehyde is 55-85°C, and the reaction time is 16-24h. The reaction is carried out under the protection of a protective gas and with stirring; the protective gas is nitrogen or argon.

3. The method for preparing a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that: In step (1), one or more of the following conditions are included: i. The molar ratio of 1,2-bis(4-formylphenoxy)ethane to 2-mercaptoethanol is 1:(2-2.3), the mass ratio of 1,2-bis(4-formylphenoxy)ethane to 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); ii. The reaction temperature of 1,2-bis(4-formylphenoxy)ethane and 2-mercaptoethanol is 15-60°C, the reaction time is 2-8h, and the reaction is carried out under stirring conditions.

4. The method for preparing a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that: In step (2), one or more of the following conditions are included: i. Solvent A is selected from 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 volume ratio of the total mass of diisocyanate and hydroxyethoxypropyl-terminated polydimethylsiloxane to solvent A is 1g:0.5-30ml, preferably 1g:0.5-18ml; 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, p-phenylene diisocyanate, p-xylylene diisocyanate or tetramethylxylylene diisocyanate; iii. The molar ratio of diisocyanate to hydroxyethoxypropyl-terminated polydimethylsiloxane is (1-13):1, preferably (3.1-5.2):1; iv. The weight average molecular weight of the hydroxyethoxypropyl terminated polydimethylsiloxane is 500 to 5000 g / mol.

5. The method for preparing a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that: In step (2), one or more of the following conditions are included: i. Hydroxyethoxypropyl-terminated polydimethylsiloxane is added dropwise into the reaction system in the form of a hydroxyethoxypropyl-terminated polydimethylsiloxane solution under stirring and protective gas protection; the type of solvent used for the hydroxyethoxypropyl-terminated polydimethylsiloxane solution is the same as 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° C., preferably 70-90° C., and the reaction time is 30-600 min, preferably 100-360 min. The reaction is carried out under stirring and protective gas protection; preferably, the protective gas is nitrogen or argon.

6. The method for preparing a high-strength and 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 comprises the steps of: mixing diisocyanate and solvent A1, adding dropwise a mixed solution of hydroxyethoxypropyl-terminated polydimethylsiloxane and solvent A2 under stirring and protective gas protection, and obtaining a solution of isocyanate-terminated prepolymer X through reaction; preferably, the types of solvent A1 and solvent A2 are the same as solvent A, and the total volume of solvent A1 and solvent A2 is the same as solvent A.

7. The method for preparing a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that: In step (2), one or more of the following conditions are included: i. Solvent B is selected from 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 1g:2-15ml, preferably 1g:2-10ml; ii. The mass ratio of 1,3-bis(hydroxypropyl)-tetramethyldisiloxane to stannous isooctanoate is 100:(0.05-5), preferably 100:(2-4.4); iii. The molar ratio of diisocyanate to 1,3-bis(hydroxypropyl)-tetramethyldisiloxane is 1:(0.3-1), preferably 1:(0.47-0.7).

8. The method for preparing a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that: In step (2), one or more of the following conditions are included: i. Solution Y is added dropwise into the solution of isocyanate-terminated prepolymer X under protective gas protection and stirring; preferably, the protective gas is nitrogen or argon; ii. The reaction temperature of the isocyanate-terminated prepolymer X solution and the solution Y is 50-100° C., preferably 70-90° C., and the reaction time is 30-480 min, preferably 30-240 min. The reaction is carried out under stirring and protective gas protection; preferably, the protective gas is nitrogen or argon.

9. The method for preparing a high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds according to claim 1, characterized in that: In step (3), one or more of the following conditions are included: i. The mass ratio of the polyhydroxy compound containing a dithioacetal bond to the diisocyanate in step (2) is 1:(3-25), preferably 1:(3-8); ii. The reaction temperature is 70-90°C, the reaction time is 30-120 min, and the reaction is carried out under stirring; iii. The curing method is as follows: let stand at room temperature for 4 to 18 hours, and then vacuum dry at 60 to 90°C for 20 to 60 hours.

10. A high-strength and high-thermoplastic-temperature polysiloxane polyurethane thermoplastic elastomer containing dynamic dithioacetal bonds, prepared by the method according to any one of claims 1 to 8.

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