Preparation method of high molecular weight silane-modified polyether

Abstract

The present invention belongs to the technical field of polyether preparation, and discloses a preparation method of a high molecular weight silane-modified polyether. The preparation method includes the following steps: preparing a low molecular weight polyether polyol; preparing a medium molecular weight polyether polyol; preparing a high molecular weight polyether polyol; and subjecting the high molecular weight polyether polyol and a silane coupling agent to a capping reaction to obtain a high molecular weight silane-modified polyether. The preparation method provided by the present invention uses a polyol as an initiator, and prepares a high molecular weight polyether polyol through a three-step method with propylene oxide, and then uses a silane coupling agent for capping to obtain a high molecular weight silane-modified polyether. The present invention prepares polyether through a three-step method, strictly controls the molecular weight and reaction temperature of the polyether polyol in each step, and adds a small molecule alcohol and an antioxidant after the reaction, so that the prepared high molecular weight silane-modified polyether has a small viscosity, strong storage stability, and small changes in viscosity and color during storage.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyether preparation, and particularly relates to a preparation method of high molecular weight silane-modified polyether. Background Art

[0002] Silane-modified polyether is a new type of organosilicon polymer. Polyether polyol is one of its important starting materials. Polyether polyols are usually obtained by ring-opening polymerization of epoxides such as ethylene oxide and propylene oxide in the presence of an initiator (such as polyol). For example, using propylene glycol as an initiator and reacting with propylene oxide, polyether polyols with different molecular weights and functionalities can be obtained. Silane coupling agent is also a key raw material for synthesizing silane-modified polyether. During the synthesis process, the alkoxy group of the silane coupling agent undergoes a condensation reaction with the hydroxyl group at the end of the polyether polyol. For example, the methoxy group (-OCH 3 3) in the silane coupling agent and the hydroxyl group (-OH) at the end of the polyether polyol, under certain reaction conditions (such as the presence of a catalyst, appropriate temperature, etc.), eliminate one molecule of methanol (CH 3 3OH), thereby introducing the silane structure into the polyether chain segment. Silane-modified polyether has good adhesion to a variety of materials. It can bond both inorganic materials such as glass, metals (aluminum, steel, etc.), and organic materials such as plastics (such as PVC, PP, etc.), wood, etc. Therefore, silane-modified polyether has extensive applications in the construction industry, automotive industry, and electronic and electrical industries. For example, in the construction industry, silane-modified polyether sealant can firmly bond glass and aluminum alloy window frames, and can withstand certain external forces and climate changes without falling off. In the automotive industry, it can be used for automotive sealing and bonding. In the electronic and electrical industries, it can be used for the encapsulation and protection of electronic components.

[0003] High molecular weight silane-modified polyether has advantages such as excellent mechanical properties and strong stability. In terms of mechanics, a higher molecular weight means longer and more complex molecular chains. During the bonding process, the silane-modified polyether molecules can form more interaction points with the surface of the bonded material, which is beneficial to improving the bonding strength; at the same time, the high molecular weight silane-modified polyether has a higher cohesive strength itself, can better resist the pulling and shearing of external forces, is not easily torn, and can maintain a good sealing effect. In terms of stability, due to the high molecular weight, the interaction between molecular chains is stronger, and higher energy is required to break the molecular chain structure. Therefore, in a high-temperature environment, it can better maintain its sealing and bonding properties and will not decompose or lose its viscosity quickly due to high temperature. In addition, high molecular weight silane-modified polyether has better resistance. Its complex molecular structure makes it difficult for chemical substances to penetrate into the interior of the molecule for reaction. The high molecular weight silane-modified polyether sealant can better resist the corrosion of chemical substances and extend the service life of the sealant.

[0004] However, as the molecular weight of silane-modified polyether increases, its viscosity also increases. Excessive viscosity will increase the difficulty in processing and operability of polyether products, such as difficulties in mixing and stirring, inconvenience in coating and construction, etc.; there is even a risk of affecting product performance. Moreover, some high-molecular-weight silane-modified polyethers also have problems such as deep color, large viscosity change during storage, and serious color deepening. Therefore, it is of great significance for its application to prepare high-molecular-weight silane-modified polyethers with low viscosity, strong storage stability, and small viscosity and color changes during storage. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. For this reason, the present invention provides a preparation method of high-molecular-weight silane-modified polyether. The high-molecular-weight silane-modified polyether prepared by the present invention has low viscosity, strong storage stability, and small viscosity and color changes during storage.

[0006] The present invention provides a preparation method of high-molecular-weight silane-modified polyether.

[0007] Specifically, a preparation method of high-molecular-weight silane-modified polyether includes the following steps:

[0008] (1) Mix a polyol with a first catalyst, dropwise add a first propylene oxide, and carry out a first polymerization reaction. After the reaction is completed, carry out post-treatment to obtain a low-molecular-weight polyether polyol;

[0009] (2) Mix the low-molecular-weight polyether polyol prepared in step (1) with a second catalyst, dropwise add a second propylene oxide, and carry out a second polymerization reaction to obtain a medium-molecular-weight polyether polyol;

[0010] (3) Mix the medium-molecular-weight polyether polyol prepared in step (2) with a third catalyst, dropwise add a third propylene oxide, and carry out a third polymerization reaction to obtain a high-molecular-weight polyether polyol;

[0011] (4) Mix the high-molecular-weight polyether polyol prepared in step (3) with a bismuth-containing catalyst, then add a silane coupling agent, and carry out a capping reaction. After the reaction is completed, sequentially add a small molecule alcohol and an antioxidant to obtain a high-molecular-weight silane-modified polyether;

[0012] The molecular weight of the low-molecular-weight polyether polyol is 300 - 800; the molecular weight of the medium-molecular-weight polyether polyol is 2 - 10 times that of the low-molecular-weight polyether polyol; the molecular weight of the high-molecular-weight polyether polyol is 2 - 10 times that of the medium-molecular-weight polyether polyol;

[0013] The temperature of the first polymerization reaction is 110 - 120 °C; the temperature of the second polymerization reaction is 125 - 145 °C; the temperature of the third polymerization reaction is 125 - 145 °C;

[0014] In step (4), the antioxidant is a phosphorus antioxidant and a phenolic antioxidant.

[0015] Preferably, the molecular weight of the low molecular weight polyether polyol is 350 - 800; the molecular weight of the medium molecular weight polyether polyol is 3 - 9 times that of the low molecular weight polyether polyol; the molecular weight of the high molecular weight polyether polyol is 3 - 9 times that of the medium molecular weight polyether polyol.

[0016] Preferably, in step (1), the polyol includes one of propylene glycol, glycerol, and glycerin.

[0017] Preferably, in step (1), the first catalyst is an alkali metal catalyst such as sodium hydroxide and potassium hydroxide. The addition amount of the first catalyst is 0.1% - 1% of the mass of the low molecular weight polyether polyol, such as 0.1% - 0.8%, 0.1% - 0.5%, 0.2% - 0.3%, etc.

[0018] Preferably, in step (1), the post - treatment process is: adding an acid and an adsorbent to the reaction system for treatment, and then dehydrating and removing the adsorbent.

[0019] Preferably, in step (2), the second catalyst is a bimetallic complex catalyst or a polymetallic complex catalyst. The addition amount of the second catalyst is 0.0015% - 0.015% of the mass of the low molecular weight polyether polyol; such as 0.0015%, 0.002%, 0.004%, 0.008%, 0.012%, 0.015%, etc.

[0020] Preferably, in step (3), the third catalyst is a bimetallic complex catalyst or a polymetallic complex catalyst. The addition amount of the third catalyst is 0.0015% - 0.015% of the mass of the medium molecular weight polyether polyol; such as 0.0015%, 0.002%, 0.004%, 0.008%, 0.012%, 0.015%, etc.

[0021] Preferably, in step (4), the bismuth - containing catalyst includes but is not limited to bismuth carboxylates, such as bismuth (2 - ethylhexanoate), bismuth neodecanoate, or bismuth tetramethylheptanedioate.

[0022] Preferably, in step (4), the addition amount of the bismuth - containing catalyst is 0.05% - 0.2% of the mass of the high molecular weight silane - modified polyether, such as 0.08%, 0.1%, 0.15%, etc.

[0023] Preferably, in step (4), the temperature of the capping reaction is 70 - 90 °C, and the time of the capping reaction is 1 - 5 hours.

[0024] Preferably, in step (4), the silane coupling agent is an isocyanate silane, such as isocyanate propyltriethoxysilane, isocyanate propyltrimethoxysilane.

[0025] Preferably, in step (4), the small molecule alcohol is selected from at least one of methanol, ethanol, propanol, isopropanol, butanol, and isobutanol.

[0026] Preferably, in step (4), the mass ratio of the phosphorus antioxidant to the phenolic antioxidant is 1:(0.5 - 2); further preferably, in step (4), the mass ratio of the phosphorus antioxidant to the phenolic antioxidant is 1:(0.8 - 1.5).

[0027] Preferably, in step (4), the phosphorus antioxidant includes tris(2,4 - di - tert - butylphenyl) phosphite (antioxidant 168) and / or antioxidant 619; the phenolic antioxidant includes at least one of 2,6 - di - tert - butyl - 4 - methylphenol (antioxidant BHT), octadecyl 3,5 - di - tert - butyl - 4 - hydroxyphenylpropionate (antioxidant 1076), 3 - dodecylthiopropionic acid - 2,4 - di - tert - butylphenyl ester (antioxidant 1135).

[0028] Preferably, in step (4), the addition amount of the antioxidant is 0.04% - 0.15% of the mass of the high - molecular - weight silane - modified polyether, such as 0.05%, 0.08%, 0.1%, 0.15%, etc.

[0029] More specifically, a preparation method of a high - molecular - weight silane - modified polyether includes the following steps:

[0030] (1) Prepare low - molecular - weight polyether polyol: Add a first catalyst and polyol into a reaction kettle. After purging with nitrogen, heat up to 105 - 110°C and start to trial - add the first propylene oxide. During this process, the pressure is controlled at ≤0.25 Mpa, and the trial - addition time is 20 - 30 minutes; after the reaction is normal, control the pressure ≤0.30 Mpa and the temperature at 110 - 120°C, and uniformly add the first propylene oxide. After the feeding is completed, cure until the pressure no longer drops; then cool down and degas, add acid solution for neutralization, add an adsorbent for adsorption treatment, and finally filter to remove the adsorbent to obtain the low - molecular - weight polyether polyol;

[0031] (2) Preparation of medium molecular weight polyether polyol: Add the second catalyst and the low molecular weight polyether polyol prepared in step (1) to the reaction kettle. After purging with nitrogen, heat up to 125°C and start trial adding the second propylene oxide for 5 - 30 minutes. After the reaction becomes normal, control the feeding temperature at 135 - 145°C, control the pressure at <0.3 Mpa, and add the second propylene oxide at a uniform speed. After the feeding is completed, cure until the pressure no longer drops. Finally, obtain the medium molecular weight polyether polyol through degassing.

[0032] (3) Preparation of high molecular weight polyether polyol: Add the third catalyst and the medium molecular weight polyether polyol prepared in step (2) to the reaction kettle. After purging with nitrogen, heat up to 125°C and start trial adding the third propylene oxide for 5 - 30 minutes. After the reaction becomes normal, control the feeding temperature at 135 - 145°C, control the pressure at <0.3 Mpa, and add the third propylene oxide at a uniform speed. After the feeding is completed, cure until the pressure no longer drops. Finally, obtain the high molecular weight polyether polyol through degassing.

[0033] (4) Silane capping: Add the high molecular weight polyether polyol prepared in step (3) to the reaction kettle. After purging with nitrogen, heat up to 60 - 120°C and add the bismuth-containing catalyst, then add the silane coupling agent, and react at 70 - 90°C for 1 - 5 hours. After the reaction is completed, add small molecule alcohol and continue to react for 1 - 3 hours. Then add the antioxidant and stir to obtain the high molecular weight silane-modified polyether.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] The preparation method of the high molecular weight silane-modified polyether provided by the present invention uses polyol as the initiator, and through a three-step method with propylene oxide, prepares a high molecular weight polyether polyol, and then uses a silane coupling agent for capping to obtain the high molecular weight silane-modified polyether. The present invention prepares polyether through a three-step method, strictly controls the molecular weight and reaction temperature of the polyether polyol in each step, and adds small molecule alcohol and antioxidant after the reaction, so that the prepared high molecular weight silane-modified polyether has a small viscosity, strong storage stability, and small changes in viscosity and color during storage. Specific embodiments

[0036] In order to make those skilled in the art more clearly understand the technical solutions described in the present invention, the following examples are listed for illustration. It should be noted that the following examples do not limit the scope of protection required by the present invention.

[0037] Unless otherwise specified, the raw materials, reagents or devices used in the following examples and comparative examples can be obtained from conventional commercial channels or can be obtained by existing known methods.

[0038] Example 1

[0039] A preparation method of a silane-modified polyether, comprising the following steps:

[0040] (1) Preparation of low-molecular-weight polypropylene glycol: Add the catalyst potassium hydroxide (14.6 g) to the condensation reaction kettle. The initiator propylene glycol (1520 g, 20 mol) is pumped from the storage tank to the reaction kettle through a metering pump. After nitrogen replacement once, close the reaction kettle and heat up to 110°C to start trial addition of the first propylene oxide. During this process, the pressure is controlled at ≤0.25 Mpa, and the trial dropping takes about 25 minutes. After the reaction is normal, control the pressure ≤0.30 Mpa. The temperature of the first polymerization reaction is 115 - 120°C, and the remaining first propylene oxide is added uniformly. After adding all the first propylene oxide (a total of 6496 g, 112 mol), close the propylene oxide discharge valve and the reaction kettle feed valve and check the quantity. Carry out aging for about 120 minutes until the pressure no longer drops. After aging is completed, cool down to 100°C, turn on the vacuum pump, and slowly open the vacuum valve to degas. The vacuum is -0.096 Mpa, and normal degassing takes 30 minutes. Transfer the material to the post-treatment kettle, add the calculated amount of phosphoric acid (30 g) to neutralize potassium hydroxide, add the adsorbent (30 g) and water (400 g), stir to adsorb phosphate, and then dehydrate under vacuum. Part of the produced wastewater is recycled, and part is discharged to the factory sewage treatment station for treatment. After the dehydrated polyether is filtered through a closed filter to remove the adsorbent, the post-treated low-molecular-weight polypropylene glycol (7986 g) is obtained.

[0041] (2) Preparation of medium-molecular-weight polypropylene glycol: Add the bimetallic complex catalyst (0.7 g) and low-molecular-weight polypropylene glycol (1597.2 g) to the condensation reaction kettle. After nitrogen replacement once, close the reaction kettle and heat up to 125°C to start trial addition of the second propylene oxide. When the pressure in the kettle is 0.25 Mpa and the temperature is 140 - 145°C, carry out the reaction for 20 min. After the reaction is normal, control the temperature of the second polymerization reaction at 140 - 145°C and the pressure at <0.3 Mpa, and add the second propylene oxide uniformly. After adding all the second propylene oxide (a total of 10393.6 g, 179.2 mol), age for 1 hour, then cool down to 100°C to degas for 30 minutes, and cool down to 70°C to discharge the material, obtaining medium-molecular-weight polypropylene glycol (11990.57 g).

[0042] (3) Preparation of high molecular weight polypropylene glycol: Add a bimetallic complex catalyst (0.35 g) and medium molecular weight polypropylene glycol (749.43 g) to the condensation reactor. Replace the air with nitrogen three times, seal the reactor, and heat up to 125 °C to start trial-adding the third propylene oxide. When the pressure in the reactor is 0.25 Mpa and the temperature is 140 - 145 °C, carry out the reaction for 20 min. After the reaction is normal, control the temperature of the third polymerization reaction at 140 - 145 °C and the pressure at <0.3 Mpa, and add the third propylene oxide at a constant speed. After adding all the third propylene oxide (a total of 2250.4 g, 38.8 mol), age for 1 hour, then cool down to 100 °C to degas for 30 minutes, and cool down to 70 °C to discharge the material, obtaining high molecular weight polypropylene glycol (2999.86 g).

[0043] (4) Silane end-capping: Add high molecular weight polypropylene glycol (5999.73) to the reaction kettle. After replacing the air with nitrogen once, heat up to 60 - 120 °C, add bismuth neodecanoate (6 g) and stir, then add the silane coupling agent. After dropping, keep the temperature at 78 - 80 °C for heat preservation reaction for 3 hours. After the heat preservation is completed, add methanol and continue the reaction for 1 - 3 hours. After the heat preservation is completed, add antioxidant 619 (3 g) and antioxidant BHT (3 g), stir and cool to discharge the material.

[0044] Example 2

[0045] A preparation method of silane-modified polyether, comprising the following steps:

[0046] (1) Preparation of low molecular weight polypropylene glycol: Add catalyst potassium hydroxide (24 g) to the condensation reactor. The initiator of propylene glycol (1520 g, 20 mol) is pumped from the storage tank to the reactor through a metering pump. Replace the air with nitrogen once, seal the reactor, and heat up to 110 °C to start trial-adding the first propylene oxide. During this process, control the pressure at ≤0.25 Mpa and trial-drop for about 25 minutes. After the reaction is normal, control the pressure at ≤0.30 Mpa and the temperature of the first polymerization reaction at 110 - 115 °C, and add the remaining first propylene oxide at a constant speed. After adding all the first propylene oxide (a total of 10480 g, 180 mol), close the propylene oxide discharge valve and the reactor feed valve and check the quantity, and carry out aging for about 120 minutes until the pressure does not drop. After aging is completed, cool down to 100 °C, turn on the vacuum pump, and slowly open the vacuum valve to degas. The vacuum is -0.096 Mpa, and normal degassing is carried out for 30 minutes. Transfer the material to the post-treatment kettle, add the calculated amount of phosphoric acid (49.5 g) to neutralize potassium hydroxide, add the adsorbent (40 g) and water (400 g), stir and adsorb phosphates, then dehydrate under vacuum. Part of the produced wastewater is recycled and part is discharged to the factory sewage treatment station for treatment. After the dehydrated polyether is filtered through a closed filter to remove the adsorbent, the post-treated low molecular weight polypropylene glycol (11960 g) is obtained.

[0047] (2) Preparation of medium molecular weight polypropylene glycol: Add bimetallic complex catalyst (0.95 g) and low molecular weight polypropylene glycol (2392 g) into the condensation reactor. Replace the air with nitrogen once, seal the reactor, and heat up to 120 °C to start trial addition of the second propylene oxide. When the pressure in the reactor is 0.25 Mpa and the temperature is 135 - 140 °C, carry out the reaction for 25 min. After the reaction is normal, control the temperature of the second polymerization reaction at 135 - 140 °C, control the pressure < 0.3 Mpa, and add the second propylene oxide at a uniform speed. After adding all the second propylene oxide (a total of 15613.6 g, 269.2 mol), age for 1 hour, then cool down to 100 °C to degas for 30 minutes, and cool down to 70 °C to discharge, obtaining medium molecular weight polypropylene glycol (18006.35 g).

[0048] (3) Preparation of high molecular weight polypropylene glycol: Add bimetallic complex catalyst (0.5 g) and medium molecular weight polypropylene glycol (1125.4 g) into the condensation reactor. Replace the air with nitrogen three times, seal the reactor, and heat up to 120 °C to start trial addition of the third propylene oxide. When the pressure in the reactor is 0.25 Mpa and the temperature is 135 - 140 °C, carry out the reaction for 20 min. After the reaction is normal, control the temperature of the third polymerization reaction at 135 - 140 °C, control the pressure < 0.3 Mpa, and add the third propylene oxide at a uniform speed. After adding all the third propylene oxide (a total of 3375.6 g, 58.2 mol), age for 1 hour, then cool down to 100 °C to degas for 30 minutes, and cool down to 70 °C to discharge, obtaining high molecular weight polypropylene glycol (4501.18 g).

[0049] (4) Silane end-capping: Add high molecular weight polypropylene glycol (5765.78 g) into the reaction kettle. After replacing the air with nitrogen once, heat up to 60 - 120 °C, add bismuth neodecanoate (6 g) and stir, then add silane coupling agent. After dropping, keep the temperature at 78 - 80 °C for heat preservation reaction for 3 hours. After the heat preservation is over, add ethanol and continue the reaction for 1 - 3 hours. After the heat preservation is over, add antioxidant 619 (3 g) and antioxidant 1076 (3 g), stir and cool, and then discharge.

[0050] Comparative Example 1

[0051] A preparation method of silane-modified polyether, comprising the following steps:

[0052] (1) Preparation of low molecular weight polypropylene glycol: Add the catalyst potassium hydroxide (14.6 g) to the condensation reactor. The initiator, propylene glycol (1520 g, 20 mol), is pumped from the storage tank to the reactor through a metering pump. The reactor is purged with nitrogen once, sealed, and heated to 110 °C to start the trial addition of the first propylene oxide. During this process, the pressure is controlled at ≤0.25 Mpa, and the trial addition takes about 25 minutes. After the reaction is normal, control the pressure at ≤0.30 Mpa. The temperature of the first polymerization reaction is 115 - 120 °C, and the remaining first propylene oxide is added at a constant speed. After adding all the first propylene oxide (a total of 6496 g, 112 mol), close the propylene oxide discharge valve and the reactor feed valve and check the quantity. Carry out aging for about 120 minutes until the pressure no longer drops. After aging is completed, cool down to 100 °C, turn on the vacuum pump, and slowly open the vacuum valve to degas. The vacuum is -0.096 Mpa, and normal degassing takes 30 minutes. Transfer the material to the post-treatment reactor, add the calculated amount of phosphoric acid (30 g) to neutralize potassium hydroxide, add the adsorbent (30 g) and water (400 g), stir to adsorb phosphates, and then dehydrate under vacuum. Part of the produced wastewater is recycled, and part is discharged to the factory sewage treatment station for treatment. After the dehydrated polyether is filtered through a closed filter to remove the adsorbent, the post-treated low molecular weight polypropylene glycol (7986 g) is obtained.

[0053] (2) Preparation of medium molecular weight polypropylene glycol: Add the bimetallic complex catalyst (0.60 g) and low molecular weight polypropylene glycol (1597.2 g) to the condensation reactor. The reactor is purged with nitrogen once, sealed, and heated to 125 °C to start the trial addition of the second propylene oxide. When the pressure in the reactor is 0.25 Mpa and the temperature is 140 - 145 °C, the reaction proceeds for 20 min. After the reaction is normal, control the temperature of the second polymerization reaction at 140 - 145 °C and the pressure at <0.3 Mpa, and add the second propylene oxide at a constant speed. After adding all the second propylene oxide (a total of 1596.16 g, 27.52 mol), age for 1 hour, then cool down to 100 °C to degas for 30 minutes, and cool down to 70 °C to discharge the material, obtaining medium molecular weight polypropylene glycol (3193.56 g).

[0054] (3) Preparation of high molecular weight polypropylene glycol: Add the bimetallic complex catalyst (0.35 g) and medium molecular weight polypropylene glycol (199.6 g) to the condensation reactor. The reactor is purged with nitrogen three times, sealed, and heated to 125 °C to start the trial addition of the third propylene oxide. When the pressure in the reactor is 0.25 Mpa and the temperature is 140 - 145 °C, the reaction proceeds for 20 min. After the reaction is normal, control the temperature of the third polymerization reaction at 140 - 145 °C and the pressure at <0.3 Mpa, and add the third propylene oxide at a constant speed. After adding all the third propylene oxide (a total of 2800 g, 48.28 mol), age for 1 hour, then cool down to 100 °C to degas for 30 minutes, and cool down to 70 °C to discharge the material, obtaining high molecular weight polypropylene glycol (2999.87 g).

[0055] (4)Silane capping: Add high molecular weight polypropylene glycol (5999.73) into the reaction kettle. After purging with nitrogen once, heat up to 60 - 120 °C, add bismuth neodecanoate (6 g) and stir, then add silane coupling agent. After dropping, keep the temperature at 78 - 80 °C for heat preservation reaction for 3 hours. After the heat preservation is over, add methanol and continue the reaction for 1 - 3 hours. After the heat preservation is over, add antioxidant 619 (3 g) and antioxidant BHT (3 g), stir and cool, then discharge the material.

[0056] Comparative Example 2

[0057] A preparation method of silane-modified polyether, comprising the following steps:

[0058] (1)Preparation of low molecular weight polypropylene glycol: Add catalyst potassium hydroxide (14.6 g) into the condensation reaction kettle. Propylene glycol (1520 g, 20 mol) as the initiator is pumped from the storage tank to the reaction kettle through a metering pump. After purging with nitrogen once, close the reaction kettle and heat up to 110 °C to start trial addition of the first propylene oxide. During this process, the pressure is controlled at ≤0.25 Mpa, and the trial dropping takes about 25 minutes. After the reaction is normal, control the pressure ≤0.30 Mpa, and the temperature of the first polymerization reaction is 115 - 120 °C. Add the remaining first propylene oxide at a constant speed. After adding all the first propylene oxide (a total of 6496 g, 112 mol), close the propylene oxide discharge valve and the reaction kettle feed valve and check the quantity. Carry out aging for about 120 minutes until the pressure no longer drops. After aging is completed, cool down to 100 °C, turn on the vacuum pump, and slowly open the vacuum valve to degas. The vacuum is -0.096 Mpa, and normal degassing takes 30 minutes. Transfer the material to the post-treatment kettle, add the calculated amount of phosphoric acid (30 g) to neutralize potassium hydroxide, add adsorbent (30 g) and water (400 g). After stirring and adsorbing phosphates, dehydrate under vacuum. Part of the produced wastewater is recycled, and part is discharged to the factory sewage treatment station for treatment. After the dehydrated polyether is filtered through a closed filter to remove the adsorbent, the post-treated low molecular weight polypropylene glycol (7986 g) is obtained.

[0059] (2)Preparation of medium molecular weight polypropylene glycol: Add double metal complex catalyst (0.60 g) and low molecular weight polypropylene glycol (1597 g) into the condensation reaction kettle. After purging with nitrogen once, close the reaction kettle and heat up to 125 °C to start trial addition of the second propylene oxide. When the pressure in the kettle is 0.25 Mpa and the temperature is 140 - 145 °C, carry out the reaction for 20 min. After the reaction is normal, control the temperature of the second polymerization reaction at 140 - 145 °C and the pressure at <0.3 Mpa. Add the second propylene oxide at a constant speed. After adding all the second propylene oxide (a total of 1596.16 g, 27.52 mol), age for 1 hour, then cool down to 100 °C to degas for 30 minutes, and cool down to 70 °C to discharge the material, obtaining medium molecular weight polypropylene glycol (3193.56 g).

[0060] (3)Continue to prepare medium molecular weight polypropylene glycol: Add a double metal complex catalyst (0.15 g) and the medium molecular weight polypropylene glycol obtained in step (2) (199.6 g) into the condensation reactor. Replace the air with nitrogen three times, seal the reactor, and heat it up to 125 °C to start trial-adding the third propylene oxide. When the pressure in the reactor is 0.25 Mpa and the temperature is 140 - 145 °C, carry out the reaction for 20 min. After the reaction is normal, control the temperature of the third polymerization reaction at 140 - 145 °C and the pressure at <0.3 Mpa, and add the third propylene oxide at a constant speed. After adding all the third propylene oxide (a total of 200.1 g, 3.45 mol), age for 1 hour, then cool down to 100 °C to degas for 30 minutes, and cool down to 70 °C to discharge the material, obtaining medium molecular weight polypropylene glycol (399.75 g).

[0061] (4)Prepare high molecular weight polypropylene glycol: Add a double metal complex catalyst (0.35 g) and the medium molecular weight polypropylene glycol obtained in step (3) (399.75 g) into the condensation reactor. Replace the air with nitrogen three times, seal the reactor, and heat it up to 125 °C to start trial-adding the fourth propylene oxide. When the pressure in the reactor is 0.25 Mpa and the temperature is 140 - 145 °C, carry out the reaction for 20 min. After the reaction is normal, control the temperature of the fourth polymerization reaction at 140 - 145 °C and the pressure at <0.3 Mpa, and add the fourth propylene oxide at a constant speed. After adding all the fourth propylene oxide (a total of 2600.14 g, 44.83 mol), age for 1 hour, then cool down to 100 °C to degas for 30 minutes, and cool down to 70 °C to discharge the material, obtaining high molecular weight polypropylene glycol (3000.05 g).

[0062] (4)Silane end-capping: Add high molecular weight polypropylene glycol (5999.73) into the reaction kettle. After replacing the air with nitrogen once, heat it up to 60 - 120 °C, add bismuth neodecanoate (6 g) and stir, then add the silane coupling agent. After dropping, keep the temperature at 78 - 80 °C for heat preservation reaction for 3 hours. After the heat preservation is over, add methanol and continue the reaction for 1 - 3 hours. After the heat preservation is over, add antioxidant 619 (3 g) and antioxidant BHT (3 g), stir and cool to discharge the material.

[0063] Comparative Example 3

[0064] A preparation method of a silane-modified polyether, comprising the following steps:

[0065] (1) Preparation of low molecular weight polypropylene glycol: Add the catalyst potassium hydroxide (24 g) to the condensation reactor. The initiator propylene glycol (1520 g, 20 mol) is pumped from the storage tank to the reactor through a metering pump. After purging with nitrogen once, close the reactor and heat up to 110 °C to start trial adding the first propylene oxide. During this process, the pressure is controlled at ≤0.25 Mpa, and the trial dropping takes about 25 minutes. After the reaction is normal, control the pressure at ≤0.30 Mpa. The temperature of the first polymerization reaction is 115 - 120 °C. Add the remaining first propylene oxide at a uniform speed. After adding all the first propylene oxide (a total of 10480 g, 180 mol), close the propylene oxide discharge valve and the reactor feed valve and check the quantity. Carry out aging for about 120 minutes until the pressure no longer drops. After aging is completed, cool down to 100 °C, turn on the vacuum pump, and slowly open the vacuum valve to degas. The vacuum is -0.096 Mpa, and normal degassing takes 30 minutes. Transfer the material to the post-treatment reactor, add the calculated amount of phosphoric acid (49.5 g) to neutralize potassium hydroxide, add the adsorbent (40 g) and water (400 g). After stirring and adsorbing phosphates, carry out vacuum dehydration. Part of the produced wastewater is recycled and part is discharged to the factory sewage treatment station for treatment. After the dehydrated polyether is filtered through a closed filter to remove the adsorbent, the post-treated low molecular weight polypropylene glycol (11960 g) is obtained.

[0066] (2) Preparation of medium molecular weight polypropylene glycol: Add the bimetallic complex catalyst (0.9 g) and low molecular weight polypropylene glycol (2392 g) to the condensation reactor. After purging with nitrogen once, close the reactor and heat up to 125 °C to start trial adding the second propylene oxide. When the pressure in the reactor is 0.25 Mpa and the temperature is 140 - 145 °C, carry out the reaction for 20 min. After the reaction is normal, control the temperature of the second polymerization reaction at 140 - 145 °C and the pressure at <0.3 Mpa. Add the second propylene oxide at a uniform speed. After adding all the second propylene oxide (a total of 26401.6 g, 455.2 mol), carry out aging for 1 hour, then cool down to 100 °C to degas for 30 minutes, and cool down to 70 °C to discharge the material, obtaining medium molecular weight polypropylene glycol (28794.28 g).

[0067] (3) Preparation of high molecular weight polypropylene glycol: Add the bimetallic complex catalyst (0.35 g) and medium molecular weight polypropylene glycol (1799.64 g) to the condensation reactor. After purging with nitrogen three times, close the reactor and heat up to 125 °C to start trial adding the third propylene oxide. When the pressure in the reactor is 0.25 Mpa and the temperature is 140 - 145 °C, carry out the reaction for 20 min. After the reaction is normal, control the temperature of the third polymerization reaction at 140 - 145 °C and the pressure at <0.3 Mpa. Add the third propylene oxide at a uniform speed. After adding all the third propylene oxide (a total of 1948.8 g, 33.6 mol), carry out aging for 1 hour, then cool down to 100 °C to degas for 30 minutes, and cool down to 70 °C to discharge the material, obtaining high molecular weight polypropylene glycol (3748.62 g).

[0068] (4)Silane capping: Add high molecular weight polypropylene glycol (5999.73) into the reaction kettle. After purging with nitrogen once, heat up to 60 - 120 °C, add bismuth neodecanoate (6 g) and stir, then add silane coupling agent. After dropping, keep the temperature at 78 - 80 °C for heat preservation reaction for 3 hours. After the heat preservation ends, add methanol and continue the reaction for 1 - 3 hours. After the heat preservation ends, add antioxidant 619 (3 g) and antioxidant BHT (3 g), stir and cool, then discharge.

[0069] Among them, the molecular weight situations in the preparation of Examples 1 - 2 and Comparative Examples 1 - 3 are shown in Table 1.

[0070] Table 1

[0071]

[0072] Comparative Example 4

[0073] Comparative Example 4 provides a preparation method of silane - modified polyether. The difference between Comparative Example 4 and Example 1 is that: in step (1), after sealing the reaction kettle, heat up to 100 °C and start to trial - add the first propylene oxide. During this process, the pressure is controlled at ≤0.25 Mpa, and the trial dropping takes about 25 minutes. After the reaction is normal, control the pressure ≤0.30 Mpa, the temperature of the first polymerization reaction is 100 - 105 °C, and add the remaining first propylene oxide at a uniform speed; in step (2), after sealing the reaction kettle, heat up to 105 °C and start to trial - add the second propylene oxide. When the pressure in the kettle is 0.25 Mpa and the temperature is 105 - 110 °C, carry out the reaction for 20 min. After the reaction is normal, control the temperature of the second polymerization reaction at 110 - 115 °C, control the pressure <0.3 Mpa, and add the second propylene oxide at a uniform speed; in step (3), after sealing the reaction kettle, heat up to 105 °C and start to trial - add the third propylene oxide. When the pressure in the kettle is 0.25 Mpa and the temperature is 105 - 110 °C, carry out the reaction for 20 min. After the reaction is normal, control the temperature of the third polymerization reaction at 105 - 110 °C, control the pressure <0.3 Mpa, and add the third propylene oxide at a uniform speed. The remaining steps are the same as those in Example 1.

[0074] Comparative Example 5

[0075] Comparative Example 5 provided a method for preparing a silane-modified polyether. The difference between Comparative Example 5 and Example 1 was that: in step (1), after sealing the reaction kettle, the temperature was raised to 125°C and the first propylene oxide was initially added. During this process, the pressure was controlled at ≤0.25 Mpa, and the initial dropping was carried out for about 25 minutes. After the reaction was normal, the pressure was controlled at ≤0.30 Mpa, the temperature of the first polymerization reaction was 140 - 145°C, and the remaining first propylene oxide was added at a constant speed; in step (2), after sealing the reaction kettle, the temperature was raised to 125°C and the second propylene oxide was initially added. When the pressure in the kettle was 0.25 Mpa and the temperature was 140 - 145°C, the reaction was carried out for 20 min. After the reaction was normal, the temperature of the second polymerization reaction was controlled at 140 - 145°C, the pressure was controlled <0.3 Mpa, and the second propylene oxide was added at a constant speed; in step (3), after sealing the reaction kettle, the temperature was raised to 125°C and the third propylene oxide was initially added. When the pressure in the kettle was 0.25 Mpa and the temperature was 140 - 145°C, the reaction was carried out for 20 min. After the reaction was normal, the temperature of the third polymerization reaction was controlled at 140 - 145°C, the pressure was controlled <0.3 Mpa, and the third propylene oxide was added at a constant speed. The remaining steps were the same as those in Example 1.

[0076] Comparative Example 6

[0077] Comparative Example 6 provided a method for preparing a silane-modified polyether. The difference between Comparative Example 6 and Example 1 was that: in step (1), after sealing the reaction kettle, the temperature was raised to 115°C and the first propylene oxide was initially added. During this process, the pressure was controlled at ≤0.25 Mpa, and the initial dropping was carried out for about 25 minutes. After the reaction was normal, the pressure was controlled at ≤0.30 Mpa, the temperature of the first polymerization reaction was 115 - 120°C, and the remaining first propylene oxide was added at a constant speed; in step (2), after sealing the reaction kettle, the temperature was raised to 115°C and the second propylene oxide was initially added. When the pressure in the kettle was 0.25 Mpa and the temperature was 115 - 120°C, the reaction was carried out for 20 min. After the reaction was normal, the temperature of the second polymerization reaction was controlled at 115 - 120°C, the pressure was controlled <0.3 Mpa, and the second propylene oxide was added at a constant speed; in step (3), after sealing the reaction kettle, the temperature was raised to 115°C and the third propylene oxide was initially added. When the pressure in the kettle was 0.25 Mpa and the temperature was 115 - 120°C, the reaction was carried out for 20 min. After the reaction was normal, the temperature of the third polymerization reaction was controlled at 115 - 120°C, the pressure was controlled <0.3 Mpa, and the third propylene oxide was added at a constant speed. The remaining steps were the same as those in Example 1.

[0078] Comparative Example 7

[0079] The difference between Comparative Example 7 and Example 1 was that in step (4), after the heat preservation was completed, antioxidant 619 (6 g) was added, and the mixture was stirred and cooled and then discharged. The remaining steps were the same as those in Example 1.

[0080] Comparative Example 8

[0081] The difference between Comparative Example 8 and Example 1 is that in step (4), after the heat preservation is completed, antioxidant BHT (6 g) is added, and then it is stirred, cooled and discharged. The remaining steps are the same as those in Example 1.

[0082] Product effect test

[0083] The performance of the silane-modified polyethers prepared in Examples 1-2 and Comparative Examples 1-8 was tested, mainly including molecular weight, viscosity, color, storage stability, free isocyanate content and mechanical properties (strength, elongation). The specific test methods are as follows:

[0084] (1) Color test: The color test was carried out using the platinum-cobalt colorimetric method;

[0085] (2) Viscosity: Brookfield cone-plate viscometer was used

[0086] (3) Storage stability: The silane-modified polyether product was placed in a forced-air oven at 120 °C for 6 hours, and the change in viscosity was measured;

[0087] (4) Free isocyanate content was measured by liquid chromatography;

[0088] (5) Mechanical properties (strength, elongation) were measured according to the method of GB / T 528-2009.

[0089] The test results are shown in Tables 2 and 3.

[0090] Table 2

[0091]

[0092] As can be seen from Table 2, the silane-modified polyether prepared in the examples of the present invention has a light color and a small viscosity. After high-temperature treatment, the changes in its color and viscosity are small, and it has strong high-temperature stability. By analyzing Comparative Examples 1-3, it can be seen that when the three-step method for preparing polyether is not adopted, or the molecular weights of the polyethers in each step do not meet the requirements, it is not only difficult to prepare a polyether with a preset molecular weight, but also the color, viscosity and thermal stability of the silane-modified polyether will be affected. By analyzing Comparative Examples 4-6, it can be seen that when the reaction temperature is not within the range during the polyether preparation process, it will seriously affect the actual molecular weight and it is impossible to prepare a polyether with the target molecular weight; at the same time, it will also increase the viscosity of the finally prepared silane-modified polyether, deteriorate the storage stability, and cause large changes in viscosity and color during storage. By analyzing Comparative Examples 7 and 8, it can be seen that in the preparation of silane-modified polyether, phosphorus antioxidants and phenolic antioxidants have a synergistic effect. Although the combined use of the two does not affect the initial color of the silane-modified polyether, it will greatly improve the storage stability of the silane-modified polyether and delay the color change during storage.

[0093] In addition, the peak molecular weight (Mp) and the designed molecular weight in the examples and comparative examples were analyzed. In the examples of the present invention, the actual peak molecular weight (Mp) was close to the designed molecular weight, and a silane-modified polyether with a molecular weight meeting the requirements could be prepared. There were certain differences between the peak molecular weight (Mp) of the silane-modified polyether in the comparative examples and the designed molecular weight. Among them, the peak molecular weights (Mp) of Comparative Examples 1 and 2 were much lower than the designed molecular weight. The reason was that the molecular weight difference between the second step and the first step in Comparative Example 1 was small, only doubling the molecular weight. When using a DMC catalyst for catalysis, ultra-high molecular weight by-products would be generated during the initial catalyst passivation to the just-activated stage. The smaller the molecular weight difference between the two, the higher the relative content of the ultra-high molecular weight by-products generated, and the smaller the peak molecular weight (Mp) of the final product. Similarly, the molecular weight difference between the second step and the first step in Comparative Example 2 was small, only doubling the molecular weight, and the molecular weight of the third step was also only doubled compared to the second step, making the molecular weight of Comparative Example 2 much smaller than that of Comparative Example 1. The reason why the peak molecular weight (Mp) of Comparative Example 5 was lower than the designed molecular weight was that the reaction temperature was too high during the first-step synthesis. When propylene oxide polymerized under the catalysis of the alkaline catalyst KOH, isomerization would occur at too high a temperature to form allyl alcohol or propenol, and the generated allyl alcohol or propenol would also react with propylene oxide to consume propylene oxide, resulting in a decrease in molecular weight and ultimately making the molecular weight of the entire product significantly lower than the designed molecular weight. In Comparative Examples 4 and 6, due to the too low reaction temperature in the second and third steps, and the gradually increasing molecular weight and high viscosity, the mass transfer in the reaction system was poor, the reaction was uneven, and the components with too high or too low molecular weights increased, thus causing the peak molecular weight (Mp) of the product to decrease, and the lower the reaction temperature, the more obvious the decrease. Therefore, strictly controlling the molecular weight of the polyether polyol and the reaction temperature in each step also plays an important role in preparing a silane-modified polyether meeting the set molecular weight, and neither of the two controls can be lacking.

[0094] Table 3

[0095]

[0096] As can be seen from Table 3, the silane-modified polyether prepared in the examples of the present invention has excellent mechanical properties and does not contain free isocyanate. The addition of small-molecule alcohols can eliminate the free isocyanate in the silane-modified polyether product and increase the viscosity stability and color stability of the product. In addition, as can be seen from Table 2, the larger the molecular weight of the silane-modified polyether, the higher its elongation at break.

[0097] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. A method for preparing a high molecular weight silane-modified polyether, characterized in that: The following steps are involved: (1) mixing a polyol with a first catalyst, adding a first propylene oxide dropwise, and performing a first polymerization reaction. After the reaction is completed, post-treatment is performed to obtain a low molecular weight polyether polyol; (2) mixing the low molecular weight polyether polyol prepared in step (1) with a second catalyst, adding a second propylene oxide dropwise, and performing a second polymerization reaction to obtain a medium molecular weight polyether polyol; (3) mixing the medium molecular weight polyether polyol prepared in step (2) with a third catalyst, adding a third propylene oxide dropwise, and performing a third polymerization reaction to obtain a high molecular weight polyether polyol; (4) mixing the high molecular weight polyether polyol prepared in step (3) with a bismuth-containing catalyst, then adding a silane coupling agent to carry out a capping reaction, and after the reaction is completed, sequentially adding a small molecular weight alcohol and an antioxidant to obtain a high molecular weight silane-modified polyether; The molecular weight of the low molecular weight polyether polyol is 300-800; the molecular weight of the medium molecular weight polyether polyol is 2-10 times that of the low molecular weight polyether polyol; the molecular weight of the high molecular weight polyether polyol is 2-10 times that of the medium molecular weight polyether polyol; The temperature of the first polymerization reaction is 110-120°C; the temperature of the second polymerization reaction is 125-145°C; the temperature of the third polymerization reaction is 125-145°C; In step (4), the antioxidant is a phosphorus antioxidant and a phenolic antioxidant; In step (1), the first catalyst is an alkali metal catalyst; In step (2), the second catalyst is a bimetallic complex catalyst or a multimetallic complex catalyst; In step (3), the third catalyst is a bimetallic complex catalyst or a multimetallic complex catalyst.

2. The preparation method according to claim 1, characterized in that: The molecular weight of the low molecular weight polyether polyol is 350-800; the molecular weight of the medium molecular weight polyether polyol is 3-9 times that of the low molecular weight polyether polyol; and the molecular weight of the high molecular weight polyether polyol is 3-9 times that of the medium molecular weight polyether polyol.

3. The preparation method according to claim 1 or 2, characterized in that: In step (4), the temperature of the end-capping reaction is 70-90° C., and the time of the end-capping reaction is 1-5 hours.

4. The preparation method according to claim 1 or 2, characterized in that: In step (4), the silane coupling agent is isocyanate silane.

5. The preparation method according to claim 1 or 2, characterized in that: In step (4), the small molecule alcohol is selected from at least one of methanol, ethanol, propanol, isopropanol, butanol and isobutanol.

6. The preparation method according to claim 1 or 2, characterized in that: In step (4), the mass ratio of the phosphorus antioxidant to the phenolic antioxidant is 1:(0.5-2).

7. The preparation method according to claim 6, characterized in that: In step (4), the mass ratio of the phosphorus antioxidant to the phenolic antioxidant is 1:(0.8-1.5).

8. The preparation method according to claim 6, characterized in that: In step (4), the phosphorus antioxidant includes tris(2,4-di-tert-butylphenyl)phosphite and / or antioxidant 619; the phenolic antioxidant includes at least one of 2,6-di-tert-butyl-4-methylphenol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 3-dodecylthiopropionic acid-2,4-di-tert-butylphenol ester.

9. The preparation method according to claim 7 or 8, characterized in that: In step (4), the amount of the antioxidant added is 0.04%-0.15% of the mass of the high molecular weight silane-modified polyether.

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