Method for detecting trace silicon hydroxyl in silicone oil

Abstract

The invention discloses a method for detecting trace silicon hydroxyl in silicone oil, which comprises the following steps: step S1, preparing raw materials including silicone oil, an alkoxy silane cross-linking agent and an organic tin catalyst, mixing the raw materials according to a weight ratio, putting into a container, and fully and uniformly stirring at room temperature; step S2, respectively pouring the uniformly stirred glue solution into two clean watch glass with the thickness of 100mm; s3, the watch glass containing the glue solution is placed under the room temperature condition for 5-8 hours, and if any one of the phenomena that the appearance of the glue solution becomes milky white from transparent, the surface of the glue solution is dry and the glue solution is solidified into gel from liquid occurs, it is indicated that the silicone oil to be detected contains trace silicon hydroxyl; if the phenomenon does not occur or the viscosity of the silicone oil is obviously increased, the silicone oil to be detected does not contain trace silicon hydroxyl; the raw materials required by the method are easy to obtain, and the detection process only needs to be carried out in a room temperature or constant temperature and humidity oven, so that the detection threshold and cost are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of silicone oil detection technology, and specifically to a method for detecting trace amounts of silanol groups in silicone oil. Background Technology

[0002] Silicone oils possess excellent heat resistance, insulation, weather resistance, hydrophobicity, and physiological inertness, making them widely used in electronics, building materials, petrochemicals, textile printing and dyeing, as well as pharmaceuticals, aerospace technology, and other fields. Silicone oils without silanol groups exhibit particularly outstanding performance in hydrophobicity, thermal stability, chemical inertness, electrical properties, and durability due to their highly nonpolar molecular structure, making them suitable for demanding applications such as high-temperature heat transfer oils for concentrated solar power, medical devices, precision instrument lubricants, LED encapsulation adhesives, and high-end cosmetics. However, silanol groups, as the active groups in silicone oils, even in very low concentrations, directly affect the physicochemical properties of subsequent polysiloxane products. Currently, the main detection methods for silanol-containing polysiloxanes include nuclear magnetic resonance (NMR), infrared spectroscopy, the reaction gas quantification method (responsibility to hydrogen release from LiAlH4), and volumetric methods. These methods not only require significant equipment investment and stringent testing conditions, but some also require specialized reagents and specialized testing institutions and technicians, making it impossible to perform on-the-spot quality checks on silicone oils.

[0003] Based on the above, this invention proposes a method for detecting trace amounts of silanol groups in silicone oil, which can effectively solve the above problems. Summary of the Invention

[0004] In view of the current situation of the prior art and to overcome the above-mentioned defects, the present invention provides a method for detecting trace amounts of silanol groups in silicone oil.

[0005] This invention is achieved through the following technical solution: A method for detecting trace amounts of silanol groups in silicone oil, comprising the following steps: Step S1: Prepare raw materials, including silicone oil, alkoxysilane crosslinking agent and organotin catalyst. Mix the above raw materials in a container according to the weight ratio and stir thoroughly at room temperature. Step S2: Pour the well-stirred adhesive into two 100mm clean petri dishes, controlling the thickness of the adhesive to be 1.0~1.5mm. Step S3: Place one of the petri dishes containing the adhesive solution from step S2 at room temperature for 5-8 hours. If any of the following phenomena occur: the appearance of the adhesive solution changes from transparent to milky white, the surface of the adhesive solution dries, the adhesive solution solidifies from liquid to gel, or the viscosity increases significantly, it indicates that the silicone oil to be tested contains trace amounts of silanol groups. If none of the above phenomena occur, it indicates that the silicone oil to be tested does not contain trace amounts of silanol groups. Step S4: Place the other petri dish containing the adhesive solution from step S2 in a constant temperature and humidity oven for 5-8 hours. If the adhesive solution solidifies from liquid to gel and the viscosity increases significantly, it indicates that the silicone oil to be tested contains trace amounts of silanol groups. If the adhesive solution does not gel or the viscosity does not change, it indicates that the silicone oil to be tested does not contain trace amounts of silanol groups.

[0006] According to the above technical solution, as a further preferred technical solution, in step S1, the raw materials include the following components in parts by weight: 100 parts silicone oil, 5-10 parts alkoxysilane crosslinking agent, and 1-5 parts organotin catalyst.

[0007] According to the above technical solution, as a further preferred technical solution, the silicone oil is any polysiloxane other than hydroxyl silicone oil.

[0008] According to the above technical solution, as a further preferred technical solution, the alkoxysilane crosslinking agent is any one of methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, methyltriethoxysilane oligomer, and tetraethoxysilane oligomer.

[0009] According to the above technical solution, as a further preferred technical solution, the organotin catalyst includes any one of dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctanoate, and tin complexed with dibutyltin diacetoacetate.

[0010] According to the above technical solution, as a further preferred technical solution, the temperature of the constant temperature chamber is controlled at 35-40℃ and the relative humidity is controlled at 90%-95%.

[0011] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The required raw materials, such as silicone oil, alkoxysilane crosslinking agent and organotin catalyst, are readily available, and the detection process only needs to be carried out at room temperature or in a constant temperature and humidity oven, without the need for complex and expensive instruments and equipment, which greatly reduces the threshold and cost of detection.

[0012] 2. By setting two sets of parallel tests under room temperature and constant temperature and humidity oven conditions, the test results can be mutually verified. The dual verification mechanism effectively improves the accuracy and reliability of the test results and reduces the possibility of misjudgment. Detailed Implementation

[0013] A method for detecting trace amounts of silanol groups in silicone oil, comprising the following steps: Step S1: Prepare raw materials, including silicone oil, alkoxysilane crosslinking agent and organotin catalyst. Mix the above raw materials in a container according to the weight ratio and stir thoroughly at room temperature. Step S2: Pour the well-stirred adhesive into two 100mm clean petri dishes, controlling the thickness of the adhesive to be 1.0~1.5mm. Step S3: Place one of the petri dishes containing the adhesive solution from step S2 at room temperature for 5-8 hours. If any of the following phenomena occur: the appearance of the adhesive solution changes from transparent to milky white, the surface of the adhesive solution dries, the adhesive solution solidifies from liquid to gel, or the viscosity increases significantly, it indicates that the silicone oil to be tested contains trace amounts of silanol groups. If none of the above phenomena occur, it indicates that the silicone oil to be tested does not contain trace amounts of silanol groups. Step S4: Place the other petri dish containing the adhesive solution from step S2 in a constant temperature and humidity oven for 5-8 hours. If the adhesive solution solidifies from liquid to gel and the viscosity increases significantly, it indicates that the silicone oil to be tested contains trace amounts of silanol groups. If the adhesive solution does not gel or the viscosity does not change, it indicates that the silicone oil to be tested does not contain trace amounts of silanol groups.

[0014] In this invention, if trace amounts of silanol groups (-Si-OH) are present in the silicone oil, they will undergo a condensation reaction with the alkoxy groups (-Si-OR, such as methoxy, ethoxy, etc.) in the alkoxysilane crosslinking agent under the action of an organotin catalyst, generating siloxane bonds (-Si-O-Si-) and releasing small molecules (such as methanol, ethanol). The reaction formula is as follows: -Si-OH + R'O-Si- → -Si-O-Si- + R'OH This reaction causes the molecular chains in the system to be linked by silicon-oxygen bonds, forming a cross-linked structure, which ultimately manifests as curing (geling), surface drying, or increased viscosity of the adhesive. If the silicone oil does not contain silanol groups, this reaction cannot occur, and the adhesive remains in its initial state (no gel, no significant change in viscosity).

[0015] At room temperature, organotin catalysts can slowly promote condensation reactions. As the reaction proceeds, cross-linked structures gradually form, and the adhesive exhibits phenomena such as turning milky white (due to light scattering caused by cross-linking), surface drying (due to the formation of a cross-linked film on the surface), or solidifying into a gel (due to overall cross-linking) due to the molecular chain connection.

[0016] No condensation reaction occurs, and the adhesive cannot form a cross-linked structure.

[0017] The temperature of 35–40℃ and the relative humidity of 90%–95% in a constant temperature and humidity oven are "accelerating conditions" for the condensation reaction. When the temperature increases, the molecular motion and reaction rate accelerate, making the reaction between trace amounts of silanol groups and the crosslinking agent easier and more complete. High humidity provides the trace amounts of water required for the reaction (water can indirectly promote the hydrolysis of alkoxy groups, generating more active groups to react with silanol groups), further promoting crosslinking.

[0018] Therefore, if silicone oil contains trace amounts of silanol groups, it will form crosslinks more quickly under these conditions, resulting in gelation of the adhesive or a significant increase in viscosity; if it does not contain silanol groups, there will be no crosslinking reaction, and the adhesive will not gel or the viscosity will not change.

[0019] The raw materials required for this invention, such as silicone oil, alkoxysilane crosslinking agents, and organotin catalysts, are readily available. Furthermore, the detection process only needs to be carried out at room temperature or in a constant temperature and humidity oven, eliminating the need for complex and expensive instruments and equipment, thus significantly reducing the threshold and cost of detection. By setting two sets of parallel tests under room temperature and constant temperature and humidity oven conditions, the test results can be mutually verified. This dual verification mechanism effectively improves the accuracy and reliability of the test results and reduces the possibility of misjudgment.

[0020] Furthermore, in another embodiment, in step S1, the raw materials include the following components in parts by weight: 100 parts silicone oil, 5-10 parts alkoxysilane crosslinking agent, and 1-5 parts organotin catalyst.

[0021] Furthermore, in another embodiment, the silicone oil is any polysiloxane other than hydroxyl silicone oil, specifically polydimethylsiloxane, α- or ω-terminated vinyl polydimethylsiloxane, vinyl-containing silicone oil with side chains, polydimethyl, methylethylsiloxane, polydimethyl, diphenylsiloxane, methylphenylsiloxane, methyltrifluoropropylsiloxane, methylcyanopropylsiloxane, etc.

[0022] Furthermore, in another embodiment, the alkoxysilane crosslinking agent is any one of methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, methyltriethoxysilane oligomer, and tetraethoxysilane oligomer.

[0023] Furthermore, in another embodiment, the organotin catalyst comprises any one of dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctanoate, and tin complexed with ethyl dibutyltin diacetoate.

[0024] Furthermore, in another embodiment, the temperature of the constant temperature chamber is controlled at 35-40°C, and the relative humidity is controlled at 90%-95%.

[0025] Unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" in this invention should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for detecting trace amounts of silanol groups in silicone oil, characterized in that: Includes the following steps: Step S1: Prepare raw materials, including silicone oil, alkoxysilane crosslinking agent and organotin catalyst. Mix the above raw materials in a container according to the weight ratio and stir thoroughly at room temperature. Step S2: Pour the well-stirred adhesive into two 100mm clean petri dishes, controlling the thickness of the adhesive to be 1.0~1.5mm. Step S3: Place one of the petri dishes containing the adhesive solution from step S2 at room temperature for 5-8 hours. If any of the following phenomena occur: the appearance of the adhesive solution changes from transparent to milky white, the surface of the adhesive solution dries, the adhesive solution solidifies from liquid to gel, or the viscosity increases significantly, it indicates that the silicone oil to be tested contains trace amounts of silanol groups. If none of the above phenomena occur, it indicates that the silicone oil to be tested does not contain trace amounts of silanol groups. Step S4: Place the other petri dish containing the adhesive solution from step S2 in a constant temperature and humidity oven for 5-8 hours. If the adhesive solution solidifies from liquid to gel and the viscosity increases significantly, it indicates that the silicone oil to be tested contains trace amounts of silanol groups. If the adhesive solution does not gel or the viscosity does not change, it indicates that the silicone oil to be tested does not contain trace amounts of silanol groups.

2. The method for detecting trace amounts of silanol groups in silicone oil according to claim 1, characterized in that: In step S1, the raw materials include the following components in parts by weight: 100 parts silicone oil, 5-10 parts alkoxysilane crosslinking agent, and 1-5 parts organotin catalyst.

3. The method for detecting trace amounts of silanol groups in silicone oil according to claim 1, characterized in that: The silicone oil refers to all polysiloxanes other than hydroxyl silicone oil.

4. The method for detecting trace amounts of silanol groups in silicone oil according to claim 1, characterized in that: The alkoxysilane crosslinking agent is any one of methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, methyltriethoxysilane oligomer, and tetraethoxysilane oligomer.

5. The method for detecting trace amounts of silanol groups in silicone oil according to claim 1, characterized in that: The organotin catalyst includes any one of dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctanoate, and tin complexed with ethyl dibutyltin diacetate.

6. The method for detecting trace amounts of silanol groups in silicone oil according to claim 1, characterized in that: The temperature of the constant temperature chamber is controlled at 35-40℃, and the relative humidity is controlled at 90%-95%.