Method for improving activity of silane coupling agent and reducing emission of VOCs
By using a pre-hydrolysis-de-alcoholization process, the degree of hydrolysis of silane coupling agents and the recovery of alcohols are precisely controlled, solving the problems of low activity and high VOC emissions of silane coupling agents, and achieving efficient and environmentally friendly modification of silane coupling agents.
Patent Information
- Application Number
- CN202511398007.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-28
- Publication Date
- 2025-11-21
AI Technical Summary
Silane coupling agents have low reactivity and require high temperature, high shear, and long reaction time, resulting in high energy consumption, low efficiency, and the hydrolysis process generates a large amount of VOCs emissions and is prone to condensation and deactivation.
A pre-hydrolysis-de-alcoholization process was adopted. By precisely controlling the degree of hydrolysis and adding polycondensation inhibitors, combined with vacuum distillation or reverse osmosis to remove alcohols, a highly active silane coupling agent was prepared and stored at low temperature.
It significantly enhances the reactivity of silane coupling agents, reduces VOC emissions, enables the recycling of alcohols, improves modification effects, and is environmentally friendly and efficient.
Smart Images
Figure CN120987995A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of powder modification technology, specifically a method for improving the activity of silane coupling agents and reducing VOC emissions. Background Technology
[0002] Silane coupling agents, as important interface modifiers, are widely used in rubber, plastics, coatings, and composite materials to improve the interfacial compatibility and bonding strength between inorganic fillers and organic matrices. However, silane coupling agents themselves have low reactivity, and in practical applications, they often require long-term reactions under high temperature and high shear conditions to complete the modification, resulting in high energy consumption and low efficiency. To improve their reactivity, a pre-hydrolysis method is often used, that is, reacting the silane coupling agent with water before use to hydrolyze its alkoxy groups (-OR) into silanol groups (-SiOH), which have higher reactivity.
[0003] Although hydrolysis can effectively enhance the activity of silane coupling agents, the process releases a large amount of alcohol byproducts (such as ethanol and methanol). These substances are directly emitted into the atmosphere as volatile organic compounds (VOCs), causing environmental pollution and resource waste. Taking the tire industry as an example, according to data from the U.S. Environmental Protection Agency, for every ton of rubber compounded, approximately 40 kg of alcohol VOCs are generated due to in-situ modification of silica. Furthermore, hydrolyzed silane coupling agents are prone to condensation polymerization, forming oligomers or even gels, leading to decreased activity or even inactivation, thus limiting their practical application. Summary of the Invention
[0004] The purpose of this invention is to provide a method for improving the activity of silane coupling agents and reducing VOC emissions, so as to solve the problems of low activity of silane coupling agents, high energy consumption of modification, large VOC emissions, and easy deactivation by condensation after hydrolysis in the above-mentioned background art.
[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for improving the activity of silane coupling agents and reducing VOC emissions, characterized by the following steps: (1) preparation of hydrolysate: water and dispersing solvent are prepared into an aqueous dispersion, and the aqueous dispersion is added dropwise to the silane coupling agent and mixed evenly to obtain a premix; (2) precise hydrolysis of silane coupling agent: acid is added to the premix to adjust the pH to acidic, and the mixture is continuously stirred at a temperature of 5-70°C to make the silane coupling agent reach a specific degree of hydrolysis, thereby obtaining a silane coupling agent hydrolysate; (3) de-alcoholization of hydrolysate: the hydrolysate is de-alcoholized by vacuum distillation, reverse osmosis or pervaporation to remove some or all of the alcohols produced by hydrolysis, thereby obtaining a highly active silane coupling agent; a polycondensation inhibitor is added to the de-alcoholized hydrolysate to prevent polycondensation deactivation, and the hydrolysate is stored at low temperature for later use.
[0006] Preferably, in the hydrolysate preparation step, the dispersing solvent is one or more of ethanol, methanol, or n-propanol, and the water mass concentration in the aqueous dispersion is 0.1%-100%.
[0007] Preferably, in the hydrolysate preparation step, the molar ratio of water to silane coupling agent is 1:1 to 300:1.
[0008] Preferably, the silane coupling agent is one or more of Si69, Si75, KH580, KH550, KH570, KH560 or NXT.
[0009] Preferably, in the precise hydrolysis step of the silane coupling agent, the pH of the solution is adjusted to 0.1-6 by adding formic acid, oxalic acid, acetic acid, sulfuric acid, hydrochloric acid or nitric acid, and stirred at 5-70°C for 0.5-200 hours to hydrolyze the silane coupling agent to a specific degree.
[0010] Preferably, in the hydrolysate de-alcoholization step, when vacuum distillation is used, the operating conditions are a vacuum degree of 10-3000 Pa and a temperature of 5-70 °C; when reverse osmosis is used, the operating pressure is 0.5-30 MPa.
[0011] Preferably, in the hydrolysate de-alcoholization step, the removed alcohols are recovered and recycled as a dispersing solvent in the hydrolysate, or used to prepare solid alcohol, or purified for use as industrial alcohol.
[0012] Preferably, after the de-alcoholization step of the hydrolysate, 0.02%-5% of a polycondensation inhibitor is added to the de-alcoholized hydrolysate, wherein the polycondensation inhibitor is one or more of formic acid, acetic acid, oxalic acid, acetaldehyde, or formaldehyde.
[0013] Preferably, the highly active silane coupling agent is stored at low temperatures (-20°C to 10°C) to maintain its reactivity.
[0014] Preferably, the alcohol content in the highly active silane coupling agent is less than 10%, and the proportion of its monomer hydrolysis products is higher than 70% as detected by nuclear magnetic resonance silicon spectroscopy, indicating that no significant polycondensation has occurred.
[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: The method described in this invention, through a "pre-hydrolysis-de-alcoholization" process, achieves a significant improvement in the reactivity of silane coupling agents and an effective reduction in VOC emissions. The pre-hydrolysis process allows for precise control of the degree of hydrolysis, yielding highly active monomer hydrolysis products. The de-alcoholization process centrally recovers alcohol byproducts, avoiding their direct emission as VOCs. Simultaneously, the recovered alcohols can be recycled, conforming to the concept of green chemistry. The addition of polycondensation inhibitors and low-temperature storage further ensure the stability of the highly active silane coupling agents. This method is simple, highly controllable, environmentally friendly, and efficient, applicable to various silane coupling agents, and has broad application prospects. Attached Figure Description
[0016] Figure 1 This is a schematic flowchart of a method for improving the activity of silane coupling agents and reducing VOC emissions according to the present invention.
[0017] Figure 2 The image shows the silicon NMR spectra of M1 before and after alcohol removal, representing a method for improving the activity of silane coupling agents and reducing VOC emissions according to the present invention.
[0018] Figure 3 The image shows the silicon NMR spectra of M2 before and after alcohol removal, representing a method for improving the activity of silane coupling agents and reducing VOC emissions according to the present invention.
[0019] Figure 4 The image shows the silicon NMR spectra of M3 before and after alcohol removal, representing a method for improving the activity of silane coupling agents and reducing VOC emissions according to the present invention.
[0020] Figure 5 The infrared spectrum of the modified silica is shown in the present invention, which describes a method for improving the activity of silane coupling agents and reducing VOC emissions.
[0021] Figure 6 This diagram shows the amount of coupling agent grafted onto the surface of silica after modification with different modifiers, representing a method for improving the activity of silane coupling agents and reducing VOC emissions according to the present invention. Detailed Implementation
[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0023] Example 1
[0024] Please see Figure 1-6 This invention provides a technical solution: a method for improving the activity of silane coupling agents and reducing VOC emissions, comprising the following steps:
[0025] (1) Preparation of hydrolysate: Using ethanol as the dispersion solvent, prepare a 20% aqueous dispersion with distilled water. Then, according to the molar ratio of water to silane coupling agent KH580 (MPTS) of 1:1, add an appropriate amount of aqueous dispersion to the silane coupling agent at a magnetic stirring speed of 400 rpm, mix evenly and set aside.
[0026] (2) Precise hydrolysis of silane coupling agent: Using formic acid as a pH adjuster, the pH of the well-stirred hydrolysate was adjusted to 3.5, and the mixture was continuously stirred at room temperature (25℃). The hydrolysis products of KH580 were tested using nuclear magnetic resonance spectroscopy (the NMR spectrum is shown in Figure 1). Figure 2 (As shown), after hydrolysis is complete, freeze and store for later use.
[0027] (3) De-alcoholization of hydrolysate: The KH580 hydrolysate was distilled under reduced pressure for 45 minutes at a vacuum of 0.01 MPa and 30°C. The concentration of alcohols in the hydrolysate decreased from 32.7% to 5.3%, with a de-alcoholization rate of 84%. 0.2% acetic acid was added to the hydrolysate to prepare a highly active primary KH580 hydrolysate M1. Its reactivity was determined based on NMR spectroscopy (its NMR spectrum is shown in Figure 1). Figure 2 (as shown), and store frozen at -10℃ for later use.
[0028] Example 2
[0029] Please see Figure 1-6 This invention provides a technical solution: a method for improving the activity of silane coupling agents and reducing VOC emissions, comprising the following steps:
[0030] (1) Preparation of hydrolysate: Using ethanol as the dispersion solvent, prepare a 20% aqueous dispersion with distilled water. Then, according to the molar ratio of water to silane coupling agent KH580 (MPTS) of 2:1, add an appropriate amount of aqueous dispersion to the silane coupling agent at a magnetic stirring speed of 400 rpm, mix evenly and set aside.
[0031] (2) Precise hydrolysis of silane coupling agent: Using acetic acid as a pH adjuster, the pH of the well-stirred hydrolysate was adjusted to 3.5, and the mixture was continuously stirred at room temperature (25℃). The degree of hydrolysis of KH580 was tested using nuclear magnetic resonance spectroscopy (its NMR spectrum is shown in Figure 1). Figure 3 (As shown), after hydrolysis is complete, freeze and store for later use.
[0032] (3) De-alcoholization of hydrolysate: Using a reverse osmosis device, KH580 hydrolysate was de-alcoholized for 1 hour at a pressure of 1.2 MPa and a temperature of 25°C. The concentration of alcohols in the hydrolysate decreased from 51.7% to 6.3%, with a de-alcoholization rate of 88%. 0.2% oxalic acid was added to the hydrolysate to prepare a highly active secondary hydrolysate M2 of KH580. Its reactivity was determined based on NMR spectroscopy (its NMR spectrum is shown in Figure 1). Figure 3 (as shown), and store frozen at -10℃ for later use.
[0033] Example 3
[0034] Please see Figure 1-6 This invention provides a technical solution: a method for improving the activity of silane coupling agents and reducing VOC emissions, comprising the following steps:
[0035] (1) Preparation of hydrolysate: Using ethanol as the dispersion solvent, prepare a 40% aqueous dispersion with distilled water. Then, according to the molar ratio of water to silane coupling agent KH580 (MPTS) of 10:1, add an appropriate amount of aqueous dispersion to the silane coupling agent at a magnetic stirring speed of 400 rpm, mix evenly and set aside.
[0036] (2) Precise hydrolysis of silane coupling agent: Using acetic acid as a pH adjuster, the pH of the well-stirred hydrolysate was adjusted to 3.5, and the mixture was continuously stirred at room temperature (25℃). The degree of hydrolysis of KH580 was tested using nuclear magnetic resonance spectroscopy (its NMR spectrum is shown in Figure 1). Figure 4 (As shown), after hydrolysis is complete, freeze and store for later use.
[0037] (3) De-alcoholization of hydrolysate: Using a reverse osmosis device, KH580 hydrolysate was de-alcoholized for 1 hour at a pressure of 1.2 MPa and a temperature of 25°C. The concentration of alcohols in the hydrolysate decreased from 71.7% to 7.9%, with a de-alcoholization rate of 89%. 0.3% oxalic acid was added to the hydrolysate to prepare a highly active KH580 tertiary hydrolysate M3. Its reactivity was determined based on NMR spectroscopy (its NMR spectrum is shown in Figure 1). Figure 4 (as shown), and store frozen at -10℃ for later use.
[0038] Example 4
[0039] Using a high-speed mixer as the modification equipment, silane coupling agent KH580 (8% by mass), hydrolysate M1, hydrolysate M2 and hydrolysate M3 were used as modifiers. The silica was modified for 20 min at a high-speed mixer speed of 2500 rpm and a temperature of 100℃.
[0040] The modified sample was extracted using a Soxhlet extractor with ethanol as the solvent at 75°C for 48 hours to remove the silane coupling agent physically adsorbed on the surface of the silica. Finally, the extracted silica was dried in a vacuum oven at 70°C for 4 hours, and the sample was sealed and stored for infrared spectroscopy (e.g., [insert image here]). Figure 5 (as shown) and thermogravimetric analysis (as shown) Figure 6 The modification effect was evaluated (as shown in the figure). The amount of silane coupling agent chemically adsorbed on the surface of silica was expressed as the thermogravimetric loss in the temperature range of 350-700℃.
[0041] As can be clearly seen from Examples 1-3 above, the "pre-hydrolysis-de-alcoholization" process can effectively remove more than 84% of alcohols from the silane coupling agent hydrolysate. Furthermore, NMR spectroscopy shows that the de-alcoholized silane coupling agent hydrolysate did not undergo significant polycondensation and maintained high activity. By controlling factors such as reaction time and water molar ratio, the degree of hydrolysis of the silane coupling agent can be precisely controlled.
[0042] As can be seen from Example 4, compared with unhydrolyzed KH580, the number of silanol hydroxyl groups on the surface of silica modified with the silane coupling agent after "hydrolysis-dealcoholization" is significantly reduced. Figure 5 3460cm -1 The peak at the point of application is significantly reduced, and the amount of grafting on the surface of silica is also significantly increased. Figure 6 Hydrolysis can significantly enhance the modification effect of silane coupling agents on silica. M2 showed the best modification effect on silica, indicating that the secondary hydrolysis products of silane coupling agents have the highest activity.
[0043] In summary, the "hydrolysis-de-alcoholization" process for silane coupling agents can significantly improve their reactivity and modification effect, while also enabling the concentration and utilization of alcohols. The method of this invention not only enhances the reactivity and performance of silane coupling agents but also reduces the emission of alcohol VOCs during their use. Therefore, the method of this invention has significant environmental and economic benefits and broad application prospects.
[0044] While some embodiments of the present general inventive concept have been shown and described, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined by the claims and their equivalents.
Claims
1. A method for improving the activity of silane coupling agents and reducing VOC emissions, characterized in that: The steps include: (1) Preparation of hydrolysate: water and dispersion solvent are prepared into an aqueous dispersion, and the aqueous dispersion is added dropwise to the silane coupling agent and mixed evenly to obtain a premixed solution; (2) Precise hydrolysis of silane coupling agent: Add acid to the premixed solution to adjust the pH to acidic, and stir continuously at 5-70℃ to make the silane coupling agent reach a specific degree of hydrolysis, so as to obtain the silane coupling agent hydrolysate; (3) De-alcoholization of hydrolysate: De-alcoholize the hydrolysate by vacuum distillation, reverse osmosis or pervaporation to remove some or all of the alcohols produced by hydrolysis, and obtain a highly active silane coupling agent; add a polycondensation inhibitor to the hydrolysate after de-alcoholization to prevent it from polycondensation and deactivation, and store it at low temperature for later use.
2. The method for improving the activity of silane coupling agents and reducing VOC emissions according to claim 1, characterized in that: In the hydrolysate preparation step, the dispersing solvent is one or more of ethanol, methanol, or n-propanol, and the water mass concentration in the aqueous dispersion is 0.1%-100%.
3. The method for improving the activity of silane coupling agents and reducing VOC emissions according to claim 1, characterized in that: In the hydrolysate preparation step, the molar ratio of water to silane coupling agent is from 1:1 to 300:
1.
4. The method for improving the activity of silane coupling agents and reducing VOC emissions according to claim 1, characterized in that: The silane coupling agent is one or more of Si69, Si75, KH580, KH550, KH570, KH560 or NXT.
5. The method for improving the activity of silane coupling agents and reducing VOC emissions according to claim 1, characterized in that: In the precise hydrolysis step of the silane coupling agent, the pH of the solution is adjusted to 0.1-6 by adding formic acid, oxalic acid, acetic acid, sulfuric acid, hydrochloric acid or nitric acid, and stirred at 5-70°C for 0.5-200 hours to hydrolyze the silane coupling agent to a specific degree.
6. The method for improving the activity of silane coupling agents and reducing VOC emissions according to claim 1, characterized in that: In the hydrolysate de-alcoholization step, when vacuum distillation is used, the operating conditions are a vacuum degree of 10-3000 Pa and a temperature of 5-70℃; when reverse osmosis is used, the operating pressure is 0.5-30 MPa.
7. The method for improving the activity of silane coupling agents and reducing VOC emissions according to claim 1, characterized in that: In the hydrolysate de-alcoholization step, the removed alcohols are recovered and used in a recycling process as a dispersing solvent in the hydrolysate, or for the preparation of solid alcohol, or purified for use as industrial alcohol.
8. The method for improving the activity of silane coupling agents and reducing VOC emissions according to claim 1, characterized in that: After the de-alcoholization step of the hydrolysate, 0.02%-5% of a polycondensation inhibitor is added to the de-alcoholized hydrolysate. The polycondensation inhibitor is one or more of formic acid, acetic acid, oxalic acid, acetaldehyde, or formaldehyde.
9. The method for improving the activity of silane coupling agents and reducing VOC emissions according to claim 1, characterized in that: The highly active silane coupling agent is stored at low temperatures (-20℃ to 10℃) to maintain its reactivity.
10. The method for improving the activity of silane coupling agents and reducing VOC emissions according to claim 1, characterized in that: The alcohol content in this highly active silane coupling agent is less than 10%, and according to NMR silicon spectroscopy, the proportion of its monomer hydrolysis products is higher than 70%, and no significant condensation polymerization has occurred.