Preparation method of low-cost, low-ring-body and ultralow-viscosity methyl silicone oil

Abstract

The invention belongs to the field of organic silicon synthesis, and particularly relates to a preparation method of low-cost, low-ring-body and ultralow-viscosity dimethyl silicone oil, and the viscosity of the dimethyl silicone oil is smaller than or equal to 10 cSt. The preparation method comprises the following steps: firstly, adding a hydroxyl-terminated polydimethylsiloxane linear body, a chain stopper and an activated catalyst into a reaction kettle, and carrying out hydroxyl condensation and chain segment equilibrium reaction under a negative pressure condition to obtain a polymerization precursor; then adding an end-capping reagent into the polymerization precursor, carrying out chain segment rearrangement reaction, after the reaction is finished, adding a terminator and a quenching catalyst to obtain a polymerization intermediate, and further separating to obtain a target product. The preparation method provided by the invention has the advantages of simple process, mild conditions, 100% of raw material utilization rate, and no generation of cyclosiloxane, and is suitable for green industrial production of ultralow-viscosity methyl silicone oil.

Description

Technical Field

[0001] The invention belongs to the field of silicone oil preparation, and in particular relates to a method for preparing low-ring and ultra-low-viscosity dimethyl silicone oil. Background Art

[0002] Dimethyl silicone oil is colorless and odorless with high transparency. It has the characteristics of heat resistance, cold resistance, small viscosity change with temperature, water resistance, low surface tension and physiological inertness. It is widely used in daily chemical, machinery, electrical, textile, coating, medicine and food industries.

[0003] Ultra-low viscosity dimethicone has a very wide range of application prospects in cosmetics. First, ultra-low viscosity dimethicone has excellent moisturizing ability and can be used in products such as facial moisturizers, body lotions and lipsticks to provide moisture and protection for the skin; secondly, ultra-low viscosity dimethicone has good lubrication and smooth touch, and can be used as a base oil component in cosmetics. It can help products to be pushed and applied evenly, and provide a smooth feeling to the skin. Common applications of ultra-low viscosity dimethicone in cosmetics include foundation, primer, lotion and cream.

[0004] The European Chemicals Agency (ECHA) officially announced on its official website the addition of 10 new SVHCs in the 19th batch, listing octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) as substances of very high concern, limiting the content of cyclosiloxanes. It also requires that from January 31, 2020, "rinse-off cosmetics" shall not be put on the market if the mass concentration of any substance D4, D5 and D6 is ≥ 0.1%.

[0005] In addition to the content of cyclopentadiene in the product, the viscosity of the product is also an important indicator. Different types of cosmetic products, such as lotions, foundations, lipsticks, etc., have specific requirements for the viscosity of dimethicone. Its viscosity can affect the touch and use experience of the product on the skin. Therefore, the choice of viscosity is often related to consumer preferences and the desired texture of the product. For example, some lotion products require a higher viscosity to ensure the proper texture and consistency, while some foundations may require a lower viscosity for easy application and spreading.

[0006] There are two common methods for synthesizing low-viscosity dimethyl silicone oil in the industry: one is to use methylsiloxane mixed ring (DMC) as raw material and prepare it through balanced catalyst balance. The process has a low conversion rate and the crude product contains a large amount of cyclosiloxane, which increases the difficulty of subsequent separation; the other is to use trimethylchlorosilane and dimethyldichlorosilane as raw materials to prepare low-viscosity methyl silicone oil through hydrolysis, water washing, polymerization and re-balancing. This method has a high conversion rate and produces low contents of D4, D5 and D6, but this method has complicated procedures and requires very high purity of the monomers. In addition, the reaction process will produce hydrochloric acid as a by-product, and multiple water washing and neutralization steps are required to remove acid and salt, resulting in a large amount of wastewater and waste residue, which is not environmentally friendly.

[0007] Patent CN111748097A uses trimethylchlorosilane and dimethyldichlorosilane as raw materials, and prepares ultra-low viscosity methyl silicone oil through hydrolysis, water washing, and polymerization equilibrium. This method has a high conversion rate, but the process is complicated, and hydrochloric acid is produced as a by-product during the reaction. The product needs to be washed and neutralized multiple times, generating a large amount of wastewater and waste residue.

[0008] Patent CN104059229A uses dimethylsiloxane mixed ring (DMC) and hexamethyldisiloxane (MM) as raw materials to prepare ultra-low viscosity dimethyl silicone oil through ring-opening rearrangement catalyzed by solid acid. This process does not produce wastewater or waste gas, but the conversion rate is low. The intermediate contains 15% cyclosiloxane, which increases the difficulty of separation.

[0009] Patent CN116253886A uses hydroxyl-terminated polydimethylsiloxane and hexamethyldisiloxane as raw materials to prepare low-ring ultra-low viscosity dimethyl silicone oil. The process is to condense most of the hydroxyl groups at high temperature and low negative pressure, and then cool down and add the capping agent dropwise. The remaining hydroxyl groups are eliminated by hexamethyldisilazane. The conversion rate of this process is >99%, and the ring body content is low. However, this process requires cooling during the secondary rearrangement and the capping agent is added dropwise. It has the disadvantages of complicated process, low production efficiency and high energy consumption. In addition, the raw material hexamethyldisiloxane accounts for a high proportion in the ultra-low viscosity methyl silicone oil prepared by this invention, and there is no mention of its recycling, which increases production costs. Summary of the invention

[0010] In order to solve the problems existing in the prior art, the present invention provides a method for preparing low-cost, low-ring body and ultra-low viscosity methyl silicone oil, which has mild process conditions, simple operation, low comprehensive cost and can realize large-scale industrial production. In addition, the present invention adopts a non-equilibrium catalyst, does not produce ring bodies, and reduces the difficulty of subsequent separation and purification.

[0011] A method for preparing low-cost, low-ring body and ultra-low viscosity methyl silicone oil comprises the following steps: S1. adding a hydroxyl-terminated polydimethylsiloxane linear body, a chain stopper and an activated catalyst into a reaction vessel, and performing hydroxyl condensation and chain segment rearrangement reactions under negative pressure while heating to obtain a polymer precursor; S2. Adding the end-capping agent into the reaction vessel to further perform a segment rearrangement reaction on the polymer precursor obtained in S1. After the reaction is completed, adding a quencher to obtain a polymer intermediate, which is further distilled and separated to obtain the target product, ultra-low viscosity methyl silicone oil.

[0012] The viscosity of the ultra-low viscosity methyl silicone oil is ≤10 cSt, and the contents of D4, D5 and D6 are all <0.1%.

[0013] The viscosity of the hydroxyl-terminated polydimethylsiloxane linear body is 30-100 cSt, preferably 50-90 cSt; the volatile matter is less than 0.5%, preferably less than 0.2%.

[0014] The chain stopper is dimethyl silicone oil with a viscosity of 1-10 cSt, preferably dimethyl silicone oil with a viscosity of 5-10 cSt; the amount of the chain stopper is 0.5%-10% of the linear mass of hydroxyl-terminated dimethyl silane, preferably 3%-7%.

[0015] The catalyst is activated phosphazene chloride, and the dosage is 5-20 ppm, preferably 8-10 ppm.

[0016] The activation of the chlorophosphazene is to react the chlorophosphazene catalyst with linear polydimethylsiloxane at 70° C. until the phosphazene becomes transparent.

[0017] The reaction time in S1 is 0.5-1 hour, preferably 1 hour; the reaction is carried out by heating the raw materials, specifically, the silanol groups are gradually condensed under the condition of negative pressure ≥-90 kPa, and the remaining hydroxyl groups are further condensed after the temperature reaches the target temperature of 90°C.

[0018] The end-capping agent is a combination of one or more dimethyl silicone oils with a viscosity of 0.65-5 cSt, and the mass ratio of the end-capping agent to the hydroxyl-terminated polydimethylsiloxane linear body is (0.7-2):1, preferably (1.5-2):1.

[0019] The reaction temperature in S2 is 70-120°C, preferably 90-100°C; the reaction time in S2 is 1-5 hours, preferably 2-2.5 hours.

[0020] The quencher is one or more of diethylamine, n-butylamine, hexamethyldisilazane, lithium hydroxide or magnesium hydroxide.

[0021] The beneficial effects of the present invention compared with the prior art are: 1. The present invention uses hydroxyl-terminated polydimethylsiloxane linear body as raw material and non-equilibrium catalyst to prepare ultra-low viscosity methyl silicone oil. The conversion rate is much higher than the preparation method using siloxane ring body as raw material, which has obvious cost advantage. 2. The present invention provides a method for preparing ultra-low viscosity methyl silicone oil with low cost and low energy consumption, which uses a hydroxyl-terminated linear polydimethylsiloxane as a raw material, performs hydroxyl condensation and primary segment rearrangement during the heating process of the raw material, heats the temperature to the target temperature to further condense the silanol groups, and adds a capping agent at one time. The mass ratio of the capping agent to the hydroxyl-terminated linear polydimethylsiloxane is (1.5-2):1. The reaction process does not require cumbersome processes such as cooling and dripping, and is suitable for large-scale industrial production. 3. Furthermore, the present invention uses chlorophosphazene activated by linear polydimethylsiloxane as a catalyst, and no siloxane ring is produced during the preparation of methyl silicone oil, which reduces the difficulty of subsequent distillation and purification, and provides a recycling technology for the distillation fraction, further reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart of the present invention.

[0023] Figure 2 It is a gas chromatogram of the ultra-low viscosity methyl silicone oil mixture prepared in Example 1 of the present invention.

[0024] Figure 3 It is a gas chromatogram of the ultra-low viscosity methyl silicone oil mixture prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0026] The gas chromatography conditions of the ultra-low viscosity dimethyl silicone oil prepared by the present invention are: Inlet temperature: 280°C, Split ratio: 30:1, Detector temperature: 300°C, Air flow rate 400ml / min, Nitrogen flow rate: 25ml / min, Hydrogen flow rate: 30ml / min, Column temperature: 90°C for 2 min, increase to 280°C at 15°C / min, and maintain for 55 min.

[0027] The meanings of the English abbreviations in the embodiments of the present invention are as follows: MM (hexamethyldisiloxane), MDM (octamethyltrisiloxane), MD2M (decamethyltetrasiloxane), MD3M (dodecamethylpentasiloxane) or MD4M (tetradecamethylhexasiloxane), MD5M (hexadecylheptasiloxane), MD6M (octadecyloctasiloxane), MD7M (eicosylnonasiloxane), MD8M (twendodecyldecasiloxane), MD9M (twentetradecylundecylsiloxane), MD 10 M (hexamethyldodecylsiloxane), MD 11 M (twenty-octadecyl tridesiloxane), MD 12 M (Tricontamethyltetradecylsiloxane). Hydroxyl-terminated polydimethylsilicone oil is referred to as linear body.

[0028] Example 1 Activation of phosphazene chloride catalyst: add linear phosphazene chloride catalyst into a flask, add 10cSt methyl silicone oil with a mass of 10 times that of phosphazene chloride, stir and heat to 70°C to react until transparent for use.

[0029] 1000kg of a linear solid with a viscosity of 90cSt and a volatile content of 0.15% and 70kg of a methyl silicone oil with a viscosity of 5cSt were added to the reactor, and then 8ppm of activated chlorophosphazene catalyst was added, stirring was started, and the pressure in the reactor was maintained at ≥-90kPa. After the temperature reached 90°C, the reaction was continued for 0.5 hours, and then 1000kg of MM was added at one time. The reaction temperature was controlled at 90°C. After reacting for 2 hours, hexamethyldisilazane was added to quench the catalyst to obtain low-segment polydimethylsiloxane MD. n M mixture (n=1-12), viscosity 1.71cSt, D4 content 0.05%, D5 content 0.07%, D6 content 0.04%, its specific composition is shown in Table 1, through distillation separation, 1.0cSt product MDM, 1.5cSt product MD2M and 2cSt product MD3M can be obtained, and the remaining MM, MD 4-12 M can be recycled and used as a capping agent.

[0030] Example 2 The method and steps of this embodiment are the same as those of embodiment 1, except that: the amount of MM added is 1500 kg, and the low-chain polydimethylsiloxane MD is obtained. n M mixture (n=1-12), viscosity 1.59cSt, D4 content 0.05%, D5 content 0.03%, D6 content 0.02%.

[0031] Example 3 The method and steps of this embodiment are the same as those of embodiment 1, except that: the amount of MM added is 2000 kg, and the low-chain polydimethylsiloxane MD is obtained. nM mixture (n=1-10), viscosity 1.52cSt, D4 content 0.04%, D5 content 0.02%, D6 content 0.03%.

[0032] Example 4 The method and steps of this embodiment are the same as those of Embodiment 1, except that: the amount of MM added is 700 kg, and an ultra-low viscosity methyl silicone oil polymerization intermediate is obtained with a viscosity of 1.9 cSt, a D4 content of 0.04%, a D5 content of 0.06%, and a D6 content of 0.03%.

[0033] Comparative Example 1 The method and steps of this embodiment are the same as those of Embodiment 1, except that the chlorophosphazene catalyst is diluted with toluene and then added without activation, to obtain an ultra-low viscosity methyl silicone oil polymerization intermediate with a viscosity of 1.69 cSt, a D4 content of 0.90%, a D5 content of 1.11%, and a D6 content of 0.71%.

[0034] Table 1 Ultra-low viscosity methyl silicone oil content prepared in Examples 1 to 4 and Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 MM (%) 18.24 26.91 37.21 9.67 23.69 MDM (%) 17.75 21.94 21.73 11.89 22.64 <![CDATA[MD2M(%)]]> 14.34 15.23 12.82 12.01 17.24 <![CDATA[MD3M(%)]]> 12.13 10.84 8.74 11.12 11.92 <![CDATA[MD4M(%)]]> 8.91 7.67 6.15 9.89 7.88 <![CDATA[MD5M(%)]]> 7.27 5.39 4.21 8.45 5.16 <![CDATA[MD6M(%)]]> 6.54 3.72 2.82 7.11 3.17 <![CDATA[MD7M(%)]]> 4.14 2.53 1.89 5.78 1.98 <![CDATA[MD8M(%)]]> 3.18 1.74 1.23 4.68 1.23 <![CDATA[MD9M(%)]]> 2.32 1.24 0.94 3.81 0.75 <![CDATA[MD 10 M(%)]]> 1.72 1.04 0.71 3.22 0.51 <![CDATA[MD 11 M(%)]]> 1.35 0.52 0.45 2.65 0.28 <![CDATA[MD 12 M(%)]]> 0.92 0.33 0.22 2.18 0.17 Long chain (%) 0.51 / / 7.17 0.13 <![CDATA[D4(%)]]> 0.05 0.05 0.04 0.04 0.90 <![CDATA[D5(%)]]> 0.07 0.03 0.02 0.06 1.11 <![CDATA[D6(%)]]> 0.04 0.02 0.03 0.03 0.71 The data of Example 1 and Comparative Example 1 show that the unactivated catalyst is easy to form a ring when it is low in activity, producing a low-ring substance; by activating the catalyst chlorophosphazene, the ring content can be significantly reduced, thereby improving the quality of the finished methyl silicone oil.

Claims

1. A method for preparing a low-cost, low-ring body and ultra-low viscosity methyl silicone oil, characterized in that: The following steps are involved: S1. A hydroxyl-terminated polydimethylsiloxane linear body, a chain stopper and an activated catalyst are added to a reaction vessel, and a hydroxyl condensation and a chain segment rearrangement reaction are carried out under negative pressure while heating to obtain a polymer precursor; S2. Adding the end-capping agent into the reaction vessel to further perform a segment rearrangement reaction on the polymer precursor obtained in S1. After the reaction is completed, adding a quencher to obtain a polymer intermediate, which is further distilled and separated to obtain the target product, ultra-low viscosity methyl silicone oil.

2. The method for preparing a low-cost, low-ring-body ultra-low-viscosity methyl silicone oil according to claim 1, characterized in that: The viscosity of the ultra-low viscosity methyl silicone oil is ≤10 cSt, and the contents of D4, D5 and D6 are all <0.1%.

3. The method for preparing a low-cost, low-ring-body ultra-low-viscosity methyl silicone oil according to claim 1, characterized in that: The viscosity of the hydroxyl-terminated polydimethylsiloxane linear body is 30-100 cSt, preferably 50-90 cSt; the volatile matter is less than 0.5%, preferably less than 0.2%.

4. The method for preparing a low-cost, low-ring-body and ultra-low-viscosity methyl silicone oil according to claim 1, characterized in that: The chain stopper is dimethyl silicone oil with a viscosity of 1-10 cSt, preferably dimethyl silicone oil with a viscosity of 5-10 cSt; the amount of the chain stopper is 0.5%-10% of the linear mass of hydroxyl-terminated dimethyl silane, preferably 3%-7%.

5. The method for preparing a low-cost, low-ring-body and ultra-low-viscosity methyl silicone oil according to claim 1, characterized in that: The catalyst is activated phosphazene chloride, and the dosage is 5-20 ppm, preferably 8-10 ppm.

6. The method for preparing a low-cost, low-ring-body and ultra-low-viscosity methyl silicone oil according to claim 5, characterized in that: The activation of the chlorophosphazene is to react the chlorophosphazene catalyst with linear polydimethylsiloxane at 70° C. until the phosphazene becomes transparent.

7. The method for preparing a low-cost, low-ring-body and ultra-low-viscosity methyl silicone oil according to claim 1, characterized in that: The reaction time in S1 is 0.5-1 hour, preferably 1 hour; the reaction is carried out by heating the raw materials, specifically, the silanol groups are gradually condensed under the condition of negative pressure ≥-90 kPa, and the remaining hydroxyl groups are further condensed after the temperature reaches the target temperature of 90°C.

8. The method for preparing a low-cost, low-ring-body and ultra-low-viscosity methyl silicone oil according to claim 1, characterized in that: The end-capping agent is a combination of one or more dimethyl silicone oils with a viscosity of 0.65-5 cSt, and the mass ratio of the end-capping agent to the hydroxyl-terminated polydimethylsiloxane linear body is (0.7-2):1, preferably (1.5-2):

1.

9. The method for preparing a low-cost, low-ring-body and ultra-low-viscosity methyl silicone oil according to claim 1, characterized in that: The reaction temperature in S2 is 70-120°C, preferably 90-100°C; the reaction time in S2 is 1-5 hours, preferably 2-2.5 hours.

10. The method for preparing a low-cost, low-ring-body and ultra-low-viscosity methyl silicone oil according to claim 1, characterized in that: The quencher is one or more of diethylamine, n-butylamine, hexamethyldisilazane, lithium hydroxide or magnesium hydroxide.

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