Preparation process of high-hydrophobicity silane coupling agent

Abstract

The invention discloses a preparation process of a high-hydrophobicity silane coupling agent, and belongs to the technical field of material chemistry. The preparation process of the high-hydrophobicity silane coupling agent comprises the following steps: mixing water, a solvent, a surfactant and a catalyst, dropwise adding the mixed solution into a reaction kettle containing silane, controlling the dropwise adding time within 30-60 minutes, continuously heating to 60-80 DEG C after dropwise adding is finished, keeping the temperature, and carrying out reflux heat preservation for 3-5 hours. According to the preparation process of the high-hydrophobicity silane coupling agent, short-chain silane and long-chain silane are compounded, the short-chain silane is rapidly hydrolyzed to form a cross-linked network framework, the long-chain silane is enriched on the surface to enhance hydrophobicity, efficient hydrophobicity and structural stability are achieved through cooperation of the short-chain silane and the long-chain silane, mixed liquid is dropwise added in batches, the temperature and the stirring speed are accurately controlled, and the high-hydrophobicity silane coupling agent is prepared. The local silanol concentration is prevented from being too high, the implosion phenomenon is inhibited, and the product uniformity is improved.

Description

Technical Field

[0001] The invention relates to the technical field of material chemistry, in particular to a preparation process of a highly hydrophobic silane coupling agent. Background Art

[0002] Silane coupling agents are widely used to improve the interfacial properties between inorganic materials and organic polymers, such as enhancing the mechanical strength, heat resistance, and water resistance of composite materials. However, the hydrophobicity of existing silane coupling agents in certain extreme environments still needs to be improved, especially in applications requiring high moisture resistance. To meet this growing demand, the development of a new highly hydrophobic silane coupling agent and its preparation method is particularly important. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation process for a highly hydrophobic silane coupling agent. By compounding short-chain silane and long-chain silane, the short-chain silane is rapidly hydrolyzed to form a cross-linked network skeleton, and the long-chain silane is enriched on the surface to enhance hydrophobicity. The two work together to achieve efficient hydrophobicity and structural stability, thereby solving the problems raised in the above-mentioned background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a process for preparing a highly hydrophobic silane coupling agent, comprising the following steps:

[0005] Step 1: Mix water, solvent, surfactant and catalyst, stir thoroughly until completely dissolved to form a mixed solution, and then transfer the mixed solution to a dropping tank for standby use;

[0006] Step 2: Add the silane mixture to the reactor, start the stirring device, and preheat to 30-50°C under nitrogen protection to prepare for the subsequent reaction;

[0007] Step 3: Add the mixed solution dropwise to the reactor containing silane, and the addition time is controlled within 30-60 minutes;

[0008] Step 4: After the addition is completed, continue to heat to 60-80 ° C and maintain this temperature for reflux insulation for 3-5 hours. This stage is the main reaction period. Appropriate temperature and time ensure the complete reaction;

[0009] Step 5: After the reaction is completed, the low-boiling product is collected under reduced pressure to obtain the final highly hydrophobic silane coupling agent product.

[0010] Preferably, the silane mixture is a mixture of two or more C3-C12 alkoxysilanes, and the silane mixture includes both short-chain silanes and long-chain silanes. Short-chain silanes refer to C3-C6 alkoxysilanes, which can be rapidly hydrolyzed to form a cross-linked network. Long-chain silanes refer to C9-C12 alkoxysilanes, which are enriched on the surface to enhance hydrophobicity. The ratio of short-chain silanes to long-chain silanes is 1:(1-3). Too high a proportion of long-chain silanes will result in incomplete hydrolysis and condensation.

[0011] Preferably, the solvent includes but is not limited to methanol, ethanol or isopropanol, which serves as a reaction medium and helps dissolve other components.

[0012] Preferably, the surfactant is polyethylene glycol with a molecular weight of 200-600, and the amount used is 0.5-2% of the total mass of the silane, which can reduce the surface tension of the system and improve the uniformity and stability of the mixed solution.

[0013] Preferably, a portion of polyethylene glycol is replaced by silane-modified polyether, the molecular weight of the silane-modified polyether is 5000, the silane group accounts for 30%, and the silane-modified polyether has both dispersing and hydrophobic functions.

[0014] Preferably, the catalyst includes but is not limited to hydrochloric acid or nitric acid, which is used to promote the reaction process with a concentration of 1-5 mol / L.

[0015] Preferably, the mass ratio of water, solvent, surfactant and catalyst is (8-12):(25-35):(0.4-0.6):(0.08-0.12).

[0016] Preferably, the specific method of step three is as follows:

[0017] The mixed liquid was added dropwise in 2-3 batches, with an interval of 3-10 minutes between each batch to reduce the local silanol concentration. When the total addition was completed within 60 minutes, the flow rate was controlled at 1-3 mL / min. The addition speed needed to match the condensation reaction rate to avoid excessive accumulation of the mixed liquid. During the addition phase, stirring was maintained at a medium-low speed of 200-300 rpm to avoid premature hydrolysis of the silane monomer caused by high-speed shear. Nitrogen was introduced throughout the addition process to exclude oxygen and inhibit side reactions caused by free radicals. After the addition was completed, the rotation speed was gradually increased to 400-500 rpm to promote uniform condensation of the system.

[0018] Preferably, the temperature of the added mixed liquid is controlled as follows: in the early stage of the addition, the temperature of the reactor is maintained at 30-40°C to avoid high temperature causing rapid hydrolysis and condensation of the silane monomer, which may cause local polymerization; in the later stage of the addition, the temperature is gradually raised to 60°C to promote the silanol condensation reaction, but the temperature should be avoided from exceeding 60°C to cause thermal decomposition of the long-chain silane. The early stage of the addition refers to the first 20 minutes of the addition, and the later stage of the addition refers to the 20-60 minutes of the addition.

[0019] Preferably, the specific steps of collecting low-boiling-point substances under reduced pressure are as follows:

[0020] The reaction liquid is filtered under reduced pressure through an ultrafiltration membrane with a molecular weight cutoff of 1000Da to separate the unreacted silane monomer and the reaction liquid, reducing solvent loss. The filtrate is transferred to a molecular distillation feed tank, and the parameters of the molecular distillation device are set as follows: temperature 60-80°C, pressure 0.1-1Pa, lowering vapor pressure and reducing thermal decomposition, feed rate 10-20mL / min, condensation temperature -20°C, start the vacuum pump, wait until the system pressure stabilizes below 0.5Pa, open the feed valve, control the feed rate of the distillation device, and the evaporated ethanol vapor enters the condenser for liquefaction recovery, and the residual liquid enters the collection tank to obtain the final highly hydrophobic silane coupling agent product.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The preparation process of the highly hydrophobic silane coupling agent of the present invention comprises the following steps: compounding short-chain silane and long-chain silane, wherein the short-chain silane is rapidly hydrolyzed to form a cross-linked network skeleton, and the long-chain silane is enriched on the surface to enhance hydrophobicity. The two cooperate to achieve efficient hydrophobicity and structural stability; the mixed liquid is added dropwise in batches and the temperature and stirring speed are precisely controlled to avoid excessive local silanol concentration, suppress violent polymerization, improve product uniformity, adopt molecular distillation technology to recover the solvent, reduce waste discharge, and simultaneously ultrafiltration membrane pretreatment reduces the risk of thermal decomposition of heat-sensitive long-chain silane; silane-modified polyether is introduced to replace part of polyethylene glycol, which has both dispersing and hydrophobic functions, thereby further improving product performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure is a flow chart of the preparation process of the highly hydrophobic silane coupling agent of the present invention. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0025] Example 1:

[0026] In order to solve the problem that the hydrophobic performance of existing silane coupling agents in certain extreme environments still needs to be improved, especially in application scenarios that require high moisture resistance, please refer to Figure 1 , this embodiment provides the following technical solutions:

[0027] The preparation process of a highly hydrophobic silane coupling agent comprises the following steps:

[0028] Mix 10 g of water, 30 g of ethanol, 0.5 g of polyethylene glycol (molecular weight 400), and 0.1 g of hydrochloric acid (3 mol / L), stir thoroughly until completely dissolved to prepare a mixed solution, and then transfer the mixed solution to a dropping tank for later use;

[0029] n-propyltrimethoxysilane (short chain) and dodecyltriethoxysilane (long chain) were mixed in a mass ratio of 1:2 to prepare a silane mixture, which was then added to a reactor, the stirring device was turned on, and the mixture was preheated to 35°C under nitrogen protection.

[0030] The mixture was added dropwise to the reactor in two batches over 40 minutes. The initial temperature was 35°C and the stirring speed was 250 rpm. Nitrogen was introduced throughout the addition process. The temperature was then raised to 60°C and the stirring speed was 400 rpm.

[0031] After the addition was completed, the temperature was continued to rise to 70°C and maintained at this temperature for reflux for 4 hours;

[0032] After the reaction was completed, the reaction solution was filtered through an ultrafiltration membrane (1000 Da) and molecularly distilled at a temperature of 75° C. and a pressure of 0.5 Pa to recover ethanol and obtain the final product.

[0033] Example 2:

[0034] The preparation process of a highly hydrophobic silane coupling agent comprises the following steps:

[0035] 10 g of water, 30 g of ethanol, 0.2 g of polyethylene glycol (molecular weight 400), and 0.1 g of hydrochloric acid (3 mol / L) were mixed, 0.3 g of silane-modified polyether (molecular weight 5000) was added to the mixture to replace part of the polyethylene glycol, and the mixture was stirred until completely dissolved to prepare a mixed solution, and the mixed solution was then transferred to a dropping tank for standby use;

[0036] n-Butyltriethoxysilane (short chain) and decyltrimethoxysilane (long chain) were mixed in a mass ratio of 1:1.5 to prepare a silane mixture, which was then added to a reactor, the stirring device was turned on, and the mixture was preheated to 35°C under nitrogen protection.

[0037] The mixture was added dropwise to the reactor in three batches over a period of 40 minutes. The initial temperature was 35°C and the stirring speed was 250 rpm. Nitrogen was introduced throughout the addition process. The temperature was then raised to 60°C and the stirring speed was 400 rpm.

[0038] After the addition was completed, the temperature was continued to rise to 70°C and maintained at this temperature for reflux for 4 hours;

[0039] After the reaction was completed, the reaction solution was filtered through an ultrafiltration membrane (1000 Da) and molecularly distilled at a temperature of 75° C. and a pressure of 0.3 Pa to recover ethanol and obtain the final product.

[0040] Example 3:

[0041] The preparation process of a highly hydrophobic silane coupling agent comprises the following steps:

[0042] Mix 10 g of water, 30 g of ethanol, 0.5 g of polyethylene glycol (molecular weight 400), and 0.1 g of hydrochloric acid (5 mol / L), stir thoroughly until completely dissolved to prepare a mixed solution, and then transfer the mixed solution to a dropping tank for later use;

[0043] n-Butyltriethoxysilane (short chain) and decyltrimethoxysilane (long chain) were mixed in a mass ratio of 1:1.5 to prepare a silane mixture, which was then added to a reactor, the stirring device was turned on, and the mixture was preheated to 35°C under nitrogen protection.

[0044] The mixture was added dropwise to the reactor in three batches over 60 minutes. The initial temperature was 35°C and the stirring speed was 250 rpm. Nitrogen was introduced throughout the addition process. The temperature was then raised to 60°C and the stirring speed was 400 rpm.

[0045] After the addition was completed, the temperature was continued to rise to 60°C and maintained at this temperature for reflux for 4 hours;

[0046] After the reaction was completed, the reaction solution was filtered through an ultrafiltration membrane (1000 Da) and molecularly distilled at a temperature of 75° C. and a pressure of 0.5 Pa to recover ethanol and obtain the final product.

[0047] Comparative Example 1:

[0048] Only dodecyltriethoxysilane (long chain) was used as the silane raw material, and no short chain silane was added. Other materials were the same as those in Example 1, and the silane coupling agent was prepared using the same method as in Example 1.

[0049] Comparative Example 2:

[0050] The same materials as in Example 1 were used, and the mixed solution was not added dropwise in batches. The stirring speed was maintained at 500 rpm to complete the entire dropping process. Other methods were the same as in Example 1 to prepare a silane coupling agent.

[0051] Comparative Example 3:

[0052] The same materials and methods as those in Example 1 were used to prepare a mixed solution and a silane mixture, and the silane mixture was added dropwise and refluxed for heat preservation. However, the solvent was recovered by atmospheric distillation to obtain a silane coupling agent.

[0053] Referring to GB / T 35503-2017 standard, the hydrolysis condensation rate of the silane coupling agent prepared in Examples 1 to 3 above was tested;

[0054] According to ASTM D5946-17, the silane coupling agents prepared in Examples 1 to 3 were evenly coated on the surface of a concrete test block, and the contact angle was measured after drying.

[0055] According to ISO 8310:2017, the silane coupling agent should be sealed and stored in a constant temperature box at 25°C. It should be observed once a month for delamination, precipitation or gelation, and the changes in appearance should be recorded within 6 months.

[0056] The molecular weight distribution of the silane coupling agents prepared in Examples 1 to 3 was tested according to ASTM D5296-19.

[0057] With reference to GB / T 17391-2011 standard, the thermal decomposition rates of the silane coupling agents prepared in Examples 1 to 3 were tested, and the following data were obtained:

[0058]

[0059] It can be concluded from the above table that: in the embodiment, the compounding of short-chain and long-chain silanes significantly improves the hydrophobicity, the long-chain silane is enriched on the surface to form a hydrophobic layer, and the short-chain silane ensures the integrity of the cross-linked network. When only long-chain silane is used in comparative example 1, the hydrolysis condensation rate is low, the contact angle is only 105°, and insufficient cross-linking is caused by steric hindrance. The embodiment of batch addition + medium-speed stirring makes PDI lower and the molecular weight distribution narrow. Comparative example 2 one-time addition + high-speed stirring induces local polymerization, PDI rises to 2.1, and the product gels. In the embodiment, ultrafiltration membrane pretreatment + molecular distillation makes the thermal decomposition rate <1% and the solvent recovery rate >95%. Comparative example 3 atmospheric pressure distillation causes the thermal decomposition rate of long-chain silane to be 15%. In Example 3, high-concentration hydrochloric acid shortens the reaction time, but slightly increases the risk of thermal decomposition, and a balance between rate and stability is required.

[0060] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0061] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and alterations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A process for preparing a highly hydrophobic silane coupling agent, characterized in that: The following steps are involved: Step 1: Mix water, solvent, surfactant and catalyst, stir thoroughly until completely dissolved to form a mixed solution, and then transfer the mixed solution to a dropping tank for standby use; Step 2: Add the silane mixture into the reactor, start the stirring device, and preheat to 30-50°C under nitrogen protection; Step 3: Add the mixed solution dropwise to the reactor containing silane, and the addition time is controlled within 30-60 minutes; Step 4: After the addition is completed, continue to heat to 60-80°C and maintain this temperature for reflux insulation for 3-5 hours; Step 5: After the reaction is completed, the low-boiling product is collected under reduced pressure to obtain the final highly hydrophobic silane coupling agent product.

2. The preparation process of the highly hydrophobic silane coupling agent according to claim 1, wherein: The silane mixture is a mixture of two or more C3-C12 alkoxysilanes, and the silane mixture includes both short-chain silanes and long-chain silanes. Short-chain silanes represent C3-C6 alkoxysilanes, and long-chain silanes represent C9-C12 alkoxysilanes. The ratio of short-chain silanes to long-chain silanes is 1:(1-3). Too high a proportion of long-chain silanes will result in incomplete hydrolysis and condensation.

3. The preparation process of the highly hydrophobic silane coupling agent according to claim 1, wherein: The solvent includes, but is not limited to, methanol, ethanol or isopropanol.

4. The preparation process of the highly hydrophobic silane coupling agent according to claim 1, wherein: The surfactant is polyethylene glycol with a molecular weight of 200-600, and the amount used is 0.5-2% of the total mass of the silane.

5. The preparation process of the highly hydrophobic silane coupling agent according to claim 4, wherein: The silane-modified polyether is used to replace a portion of polyethylene glycol. The molecular weight of the silane-modified polyether is 5000, and the silane group accounts for 30%. The silane-modified polyether has both dispersing and hydrophobic functions.

6. The preparation process of the highly hydrophobic silane coupling agent according to claim 1, wherein: The catalyst includes but is not limited to hydrochloric acid or nitric acid, with a concentration of 1-5 mol / L.

7. The preparation process of the highly hydrophobic silane coupling agent according to claim 1, wherein: The mass ratio of the water, solvent, surfactant and catalyst is (8-12):(25-35):(0.4-0.6):(0.08-0.12).

8. The preparation process of the highly hydrophobic silane coupling agent according to claim 1, wherein: The specific method of step three is as follows: The mixed liquid was added dropwise in 2-3 batches, with an interval of 3-10 minutes between each batch. When the total addition was completed within 60 minutes, the flow rate was controlled at 1-3 mL / min. Stirring was maintained at a medium-low speed of 200-300 rpm during the addition phase. Nitrogen was introduced throughout the addition process. After the addition was completed, the rotation speed was gradually increased to 400-500 rpm to promote uniform condensation of the system.

9. The process for preparing a highly hydrophobic silane coupling agent according to claim 8, wherein: The temperature of the dropwise added mixed solution is controlled as follows: the temperature of the reactor is maintained at 30-40°C in the early stage of dropwise addition and gradually raised to 60°C in the late stage of dropwise addition. The early stage of dropwise addition refers to the first 20 minutes of dropwise addition and the late stage of dropwise addition refers to the 20-60 minutes of dropwise addition.

10. The process for preparing a highly hydrophobic silane coupling agent according to claim 9, wherein: The specific steps of collecting low-boiling-point substances under reduced pressure are as follows: The reaction liquid was filtered under reduced pressure through an ultrafiltration membrane with a molecular weight cutoff of 1000Da to separate the unreacted silane monomer from the reaction liquid and reduce solvent loss. The filtrate was transferred to a molecular distillation feed tank, and the parameters of the molecular distillation device were set as follows: temperature 60-80°C, pressure 0.1-1Pa, feed rate 10-20mL / min, condensation temperature -20°C, and the vacuum pump was started. After the system pressure stabilized below 0.5Pa, the feed valve was opened to control the feed rate of the distillation device. The evaporated ethanol vapor entered the condenser for liquefaction recovery, and the residual liquid entered the collection tank to obtain the final highly hydrophobic silane coupling agent product.

Images