A method for preparing low-viscosity dimethyl silicone oil

Abstract

This invention discloses a method for preparing low-viscosity dimethyl silicone oil, comprising the following steps: S1, after removing moisture from the raw materials methylcyclosiloxane and end-capping agent, a polymerization reaction is carried out under the action of a catalyst until the viscosity no longer changes, obtaining a primary crude dimethyl silicone oil; S2, the obtained primary crude dimethyl silicone oil is decolorized to obtain a secondary crude dimethyl silicone oil; S3, the secondary crude dimethyl silicone oil treated in step S2 is subjected to vacuum distillation or rectification to remove boiling substances at low temperatures, obtaining finished low-viscosity dimethyl silicone oils. According to this method, dimethyl silicone oils with a viscosity of any value less than 20 mm² / s at 25°C can be prepared for use in fabric finishing agents.

Description

Technical Field

[0001] This invention belongs to the field of dimethyl silicone oil preparation technology, and specifically relates to a method for preparing low-viscosity dimethyl silicone oil. Background Technology

[0002] Dimethyl silicone oil, also known as dimethyl polysiloxane, is an organosilicon compound. It is a liquid composed of polysiloxane chains consisting of silicon atoms and methyl groups. It has low surface tension, high surface activity, excellent defoaming and anti-foaming properties, and good film-forming ability. Dimethyl silicone oil is hydrophobic, insoluble in water, provides good isolation from other substances, exhibits superior lubrication performance, and blocks moisture without affecting breathability. Furthermore, dimethyl silicone oil shows minimal viscosity change over a wide temperature range, excellent heat and acid resistance, chemical stability, a high boiling point, a low freezing point, and a wide temperature range for liquid existence. Simultaneously, dimethyl silicone oil possesses excellent electrical properties, particularly a low rate factor across various frequency ranges, low surface tension, and excellent shear resistance. Based on these superior properties, dimethyl silicone oil is widely used in various sectors of the national economy, including machinery, electrical engineering, textiles, coatings, and medicine.

[0003] In the production of dimethyl silicone oil, the industrially common method involves catalytically equilibrating low-molar-weight dimethylcyclosiloxanes (D4 or DMC) with trimethylsiloxy-terminated low-molar-weight dimethylpolysiloxanes (MDnM), followed by removal of low-molecular-weight compounds under maximum vacuum at 150-200°C. This method is generally suitable for preparing dimethyl silicone oils with viscosities higher than 50 cs. For dimethyl silicone oils with lower viscosities, this method not only results in low yield and high energy consumption, but also fails to meet the quality requirements of some specialized industries. Particularly in the personal care industry, the control of residual amounts of D4, D5, and other cyclic compounds is becoming increasingly stringent. Summary of the Invention

[0004] This invention addresses the aforementioned problems by providing a method for preparing low-viscosity dimethyl silicone oil. To achieve this objective, the technical solution provided by this invention is as follows:

[0005] In a first aspect, the present invention provides a method for preparing low-viscosity dimethyl silicone oil, comprising the following steps:

[0006] After removing moisture from the raw materials S1, methylcyclosiloxane and end-capping agent, they are polymerized under the action of a catalyst until the viscosity no longer changes, thus obtaining a primary crude product of dimethyl silicone oil.

[0007] S2. Decolorize the obtained primary crude dimethyl silicone oil to obtain secondary crude dimethyl silicone oil.

[0008] S3. The crude dimethyl silicone oil processed in step S2 is subjected to vacuum distillation or rectification to remove boiling substances at low temperatures, thereby obtaining dimethyl silicone oil products of different low viscosities.

[0009] The mass ratio of methylcyclosiloxane to end-capping agent is 1:1 to 6.

[0010] The preferred solutions for the above steps are as follows:

[0011] Preferably, in S1, the methylcyclosiloxane is selected from octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, or dimethylcyclosiloxane;

[0012] The end-capping agent is selected from at least one of hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, dodecyl siloxane, tetradecyl hexamethylsiloxane, and dimethylsiloxane.

[0013] The method for removing moisture from the raw materials of methylcyclosiloxane and end-capping agent is as follows: first, the moisture is adsorbed by molecular sieve, and then the temperature is raised to 70-80℃ in the reaction vessel and nitrogen is introduced to further remove moisture;

[0014] The catalyst is acidic clay or macroporous cationic acidic resin, and the amount of catalyst added is 0.8 kg / ton of raw material to 1.2 kg / ton of raw material.

[0015] The polymerization reaction temperature is 100–120℃, and the polymerization reaction time is 0.5–2h.

[0016] Preferably, in step S2, activated carbon is used for decolorization.

[0017] Preferably, in S3, the temperature of the vacuum distillation treatment is 120℃ to 180℃, the treatment time is 4h to 7h, and the vacuum degree is -0.2MPa to 0MPa; a vacuum distillation column is used for distillation treatment, and the separation temperature difference is 10℃.

[0018] In a second aspect, this invention provides a low-viscosity dimethyl silicone oil, prepared using the method described above. This method can be used to prepare silicone oils with a viscosity of arbitrarily less than 20 mmHg at 25°C. 2 / s of dimethyl silicone oil.

[0019] In a second aspect, the present invention provides the application of the prepared dimethyl silicone oil in the preparation of fabric finishing agents.

[0020] By adopting the above technical solution, the present invention has the following advantages and beneficial effects:

[0021] (1) The present invention sets the mass ratio of methylcyclosiloxane and methyl end-capping agent, and within this range, any material with a thickness of less than 20 mm can be prepared. 2The yield of the target product can be adjusted by changing the raw material ratio of ultra-low viscosity dimethyl silicone oil per second.

[0022] (2) Before the raw materials are added to the reactor, the present invention first adsorbs the impurities in them with an adsorbent to avoid the impurities being introduced into the reactor and not being able to be cleaned, causing the accumulation of impurities and affecting subsequent production. Then, inert gas is further introduced into the reaction vessel to further remove moisture and ensure that moisture impurities do not affect the reaction.

[0023] (3) The present invention uses distillation or vacuum distillation to separate low molecular weight components in dimethyl silicone oil. By setting the distillation conditions, the high boiling point components can be retained to the maximum extent and the low boiling point components can be separated, thereby improving the one-time yield of the reaction. Detailed Implementation

[0024] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0025] Example 1

[0026] The method for preparing low-viscosity dimethyl silicone oil provided in this embodiment includes the following steps:

[0027] S1. Octamethylcyclotetrasiloxane was used as the methylcyclosiloxane and hexamethyldisiloxane was used as the end-capping agent. The two were mixed at a mass ratio of 1:1.5 and first adsorbed through a molecular sieve. Then, the mixture was heated to 70°C in a reaction vessel and nitrogen gas was introduced for 1 hour to further remove moisture. Under the action of the catalyst acidic clay, the polymerization reaction was carried out at 100°C until the viscosity no longer changed, and dimethyl silicone oil first-grade crude product was obtained.

[0028] S2. The obtained primary crude dimethyl silicone oil is decolorized by activated carbon to obtain secondary crude dimethyl silicone oil.

[0029] S3. The secondary crude dimethyl silicone oil treated in S2 is subjected to vacuum distillation (150℃ for 5 hours, vacuum degree from -0.2MPa to 0MPa) to remove the boiling point in the low-temperature range, obtaining a viscosity of less than 20 mmHg. 2 / s of dimethyl silicone oil.

[0030] Example 2

[0031] The method for preparing low-viscosity dimethyl silicone oil provided in this embodiment includes the following steps:

[0032] S1. Decamethylcyclopentasiloxane was used as the methylcyclosiloxane and octamethyltrisiloxane was used as the end-capping agent. The two were mixed at a mass ratio of 1:2 and first adsorbed through a molecular sieve. Then, the mixture was heated to 75°C in a reaction vessel and nitrogen gas was introduced for 1 hour to further remove moisture. Under the action of the catalyst and the large-pore cationic acidic resin, the polymerization reaction was carried out at 110°C until the viscosity no longer changed, and dimethyl silicone oil first-grade crude product was obtained.

[0033] S2. The obtained primary crude dimethyl silicone oil is decolorized by activated carbon to obtain secondary crude dimethyl silicone oil.

[0034] S3. Vacuum distillation is performed on the secondary crude dimethyl silicone oil treated in S2, with a separation temperature difference of 10°C, to remove the boiling point in the low-temperature range and obtain a viscosity of less than 20 mmHg. 2 / s of dimethyl silicone oil.

[0035] Example 3

[0036] The method for preparing low-viscosity dimethyl silicone oil provided in this embodiment includes the following steps:

[0037] S1. Dimethylcyclosiloxane was used as the methylcyclosiloxane and decamethyltetrasiloxane was used as the end-capping agent. The two were mixed at a mass ratio of 1:2.5 and first adsorbed through a molecular sieve. Then, the mixture was heated to 80°C in a reaction vessel and nitrogen gas was introduced for 1 hour to further remove moisture. Under the action of the catalyst acidic clay, the polymerization reaction was carried out at 120°C until the viscosity no longer changed, and the first-grade crude dimethyl silicone oil was obtained.

[0038] S2. The obtained primary crude dimethyl silicone oil is decolorized by activated carbon to obtain secondary crude dimethyl silicone oil.

[0039] S3. The secondary crude dimethyl silicone oil treated in S2 is subjected to vacuum distillation (160℃ for 5 hours, vacuum degree from -0.2MPa to 0MPa) to remove the boiling point in the low-temperature range, obtaining a viscosity of less than 20 mmHg. 2 / s of dimethyl silicone oil.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for the preparation of a low viscosity dimethicone characterized in that, Includes the following steps: After removing moisture from the raw materials S1, methylcyclosiloxane and end-capping agent, they are polymerized under the action of a catalyst until the viscosity no longer changes, thus obtaining a primary crude product of dimethyl silicone oil. S2. Decolorize the obtained primary crude dimethyl silicone oil to obtain secondary crude dimethyl silicone oil. S3. The crude dimethyl silicone oil processed in step S2 is subjected to vacuum distillation or rectification to remove boiling substances at low temperatures, thereby obtaining dimethyl silicone oil products of different low viscosities. The mass ratio of methylcyclosiloxane to end-capping agent is 1:1 to 6.

2. The method for preparing low-viscosity dimethyl silicone oil according to claim 1, characterized in that: wherein In S1, the methylcyclosiloxane is selected from octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane or dimethylcyclosiloxane; The end-capping agent is selected from at least one of hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, dodecyl siloxane, tetradecyl hexasiloxane, and dimethylsiloxane.

3. The method for preparing low-viscosity dimethyl silicone oil according to claim 1, characterized in that: wherein, In S1, the method for removing moisture from the raw materials of methylcyclosiloxane and end-capping agent is as follows: first, the moisture is adsorbed by molecular sieve, and then the temperature is raised to 70-80°C in the reaction vessel and nitrogen gas is introduced to further remove moisture.

4. The method for preparing low-viscosity dimethyl silicone oil according to claim 1, characterized in that: wherein In S1, the catalyst is acidic clay or macroporous cationic acidic resin, and the amount of catalyst added is 0.8 kg / ton of raw material to 1.2 kg / ton of raw material; the polymerization reaction temperature is 100-120℃, and the polymerization reaction time is 0.5-2 h.

5. The method for preparing low-viscosity dimethyl silicone oil according to claim 1, characterized in that: wherein In S2, activated carbon is used for decolorization.

6. The method for preparing low-viscosity dimethyl silicone oil according to claim 1, characterized in that: wherein In S3, the temperature of vacuum distillation is 120℃ to 180℃, the treatment time is 4h to 7h, and the vacuum degree is -0.2MPa to 0MPa. In S3, a vacuum distillation column is used for distillation, with a separation temperature difference of 10℃.

7. A low viscosity dimethicone characterized in that, It is prepared by the method described in any one of claims 1 to 6.

8. The low viscosity dimethicone of claim 7, wherein, The low viscosity dimethicone is a dimethicone having a viscosity of any less than 20 mm 2 / s at 25 °C.

9. The use of the dimethyl silicone oil according to claim 7 or 8 in the preparation of fabric finishing agents.