Ultralow-viscosity octamethyltrisiloxane and decamethyltetrasiloxane purification process

Abstract

The invention provides a process for purifying ultralow-viscosity octamethyltrisiloxane and decamethyltetrasiloxane, which is characterized in that mixed methyl silicone oil is used as a raw material, and high-quality ultralow-viscosity octamethyltrisiloxane and decamethyltetrasiloxane products are respectively obtained through a rectification and adsorption synergistic separation technology. The method has the advantages that the thermal contact time of the product is shortened, the purity of the product is improved, and the equipment cost and energy consumption are reduced.

Description

Technical Field

[0001] The invention belongs to the field of organic silicone oil production, and specifically relates to a purification process for ultra-low viscosity methyl trisiloxane and decamethyl tetrasiloxane. Background Art

[0002] Low-viscosity methyl silicone oil has the advantages of high dispersibility, low surface tension, low reactivity, low vapor pressure, good thermal stability and leveling, and has good compatibility with most cosmetic ingredients. Therefore, it is widely used in the daily chemical industry, among which octamethyl trisiloxane (MDM) with a viscosity of 1.0cst and decamethyl tetrasiloxane (MD2M) with a viscosity of 1.5cst (should it be a range value, such as 0.1-1.0cst; 0.1-2.0cst) have unique application prospects in the field of cosmetics. However, compared with imported products, domestic low-viscosity methyl silicone oil has differences such as high impurity content and dark color.

[0003] Octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) have the dangerous properties of PBT and vPvB (persistent, bioaccumulative and toxic substances), which pose risks to the environment after use. The EU Reach regulation requires that the content of D4, D5 and D6 in rinse-off cosmetics must be less than 0.1%. Therefore, how to precisely separate low-viscosity silicone oil is the key to improving product quality.

[0004] CN110818900A discloses a method and production system for continuous catalytic synthesis and separation of high-purity low-viscosity methyl silicone oil. The invention uses specific synthesis conditions to obtain a low-viscosity methyl silicone oil mixture mainly containing MDM, MD2M, MD3M and MD4M, and then continuously separates and prepares MD2M, MD3M and MD4M through a separation tower. However, the content of impurities decamethylcyclopentasiloxane and dodecamethylcyclohexasiloxane in the low-viscosity methyl silicone oil obtained in the continuous production work cannot be less than 1%.

[0005] The present invention removes impurities by combining a distillation tower and an adsorption column filled with a high-efficiency adsorbent, so that the contents of D4, D5 and D6 are all less than 0.1%, thereby efficiently and energy-savingly separating high-purity ultra-low viscosity methyl silicone oil MDM and MD2M products to meet the requirements of the EU Reach regulations and solve the industry problems faced by the industry in preparing low-viscosity methyl silicone oil. Summary of the invention

[0006] In view of the above technical problems, the purpose of the present invention is to provide a purification process for ultra-low viscosity methyl trisiloxane and decamethyl tetrasiloxane, using mixed methyl silicone oil as raw material, and obtaining high-quality ultra-low viscosity octamethyl trisiloxane and decamethyl tetrasiloxane products respectively through distillation and adsorption synergistic separation technology. Compared with the prior art, the present invention reduces the heat contact time of the product, improves the purity of the product, and reduces equipment cost and energy consumption.

[0007] In the present invention, the "mixed methyl silicone oil raw material" refers to a mixture consisting of hexamethyldisiloxane (MM), octamethyltrisiloxane (MDM), decamethyltetrasiloxane (MD2M), dodecamethylpentasiloxane (MD3M) and tetradecamethylhexasiloxane (MD4M) and impurities such as hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6).

[0008] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme.

[0009] A purification process for ultra-low viscosity methyltrisiloxane and decamethyltetrasiloxane, using distillation and adsorption synergistic separation technology, specifically comprising the following steps: (1) Weight removal: The mixed methyl silicone oil raw material is input into a weight removal tower for separation. The distillate from the top of the weight removal tower is sent to a light removal tower. The distillate from the bottom of the tower is a high-boiling substance with a boiling point higher than decamethyltetrasiloxane (MD2M).

[0010] The overhead distillate comprises MM, MDM, MD2M, D3, D4, etc.; The tower bottom distillate includes D5, D6, MD3M, MD4M and MDnM (n>4) and the like.

[0011] (2) D3 Removal: The top distillate of the deheaving tower is separated by the light-removing tower [B] to remove low-boiling substances such as MM and D3 from the top of the tower. The bottom liquid containing components such as MDM, MD2M, and D4 is obtained from the bottom of the tower and sent to the MDM product tower.

[0012] (3) MDM purification: The bottom liquid of the light removal tower enters the MDM product tower for distillation, and a high-quality ultra-low viscosity MDM product is obtained from the top of the tower. The bottom liquid containing components such as MD2M and D4 is obtained from the bottom of the tower and sent to the D4 adsorption column.

[0013] (4) D4 adsorption: The kettle liquid of the MDM product tower enters the D4 adsorption column for adsorption and removal of D4 to obtain high-quality ultra-low viscosity MD2M products.

[0014] According to the present invention, the operating conditions of the deweighting tower are: pressure 7-15Kpa, temperature 150-200°C, and reflux ratio 0.5-5.

[0015] According to the present invention, the operating conditions of the lightness removal tower are: pressure 15-25Kpa, temperature 100-150°C, and reflux ratio 1-10.

[0016] According to the present invention, the operating conditions of the MDM product tower are: pressure 8-12Kpa, temperature 60-80°C, and reflux ratio 0.5-5.

[0017] According to the present invention, the D4 adsorption column preferably uses a modified MOFs material as an adsorbent, especially a porous adsorption material such as DUT-4, MOF-806 and PCN-223. The modification method is to mix the MOFs material with the phosphorylation agent in a certain proportion and stir for 8-12 hours and then age for 1-2 hours. The material obtained after aging is sintered at 300-450°C to obtain a phosphoric acid modified adsorbent.

[0018] The phosphorylation agent is selected from any one of aluminum dihydrogen phosphate, dialkyl phosphate, ammonium dihydrogen phosphate, ammonium hydrogen phosphate, disodium hydrogen phosphate or sodium hypophosphite.

[0019] Preferably, the bulk density of the phosphoric acid modified adsorbent is 0.35-0.9 g / mL, more preferably 0.4-0.6 g / mL; Preferably, the specific surface area of ​​the phosphoric acid modified adsorbent is 100-350m 2 / g, and the pore volume is 0.4-1.0mL / g.

[0020] According to the present invention, the operating conditions of the D4 adsorption step are: pressure 0.05-0.5 MPaG, temperature 20-60°C.

[0021] According to the present invention, after the adsorption column is saturated with adsorption, it can be regenerated by conventional methods, such as hot nitrogen regeneration, vacuum regeneration, vacuum-assisted hot nitrogen regeneration, etc.

[0022] According to the present invention, the obtained high-purity MDM has an MD2M content greater than 99.9%, and the contents of D3, D4, D5 and D6 are all less than 0.05%.

[0023] Features and effects of the present invention: Low-viscosity methyl silicone oil generates a lot of impurity components during the synthesis process, and the impurities and the boiling points of the products are staggered. When the products are separated by distillation, the heat contact time of the materials is too long, and it is difficult to ensure the purity and color of the products. The present invention adopts distillation and adsorption synergistic separation technology to reduce the heat contact time, reduce equipment costs and energy consumption. After the adsorption is completed, the modified adsorbent can be recycled after desorption and regeneration. When used for the seventh time, the absorption rate of D4 can still reach more than 95%, which provides a feasible method for the efficient and selective removal of D4 from low-viscosity methyl silicone oil, and has application and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 The invention discloses a purification process for ultra-low viscosity octamethyltrisiloxane and decamethyltetrasiloxane.

[0026] In the figure: A. Heavy removal tower, B. Light removal tower, C. MDM product tower, D. D4 adsorption column.

[0027] 1. Mixed methyl silicone oil raw material, 2. Heavy removal tower [A] overhead distillate, 3. Heavy removal tower [A] bottom liquid, 4. Light removal tower [B] overhead distillate, 5. Light removal tower [B] bottom liquid, 6. MDM product, 7. MDM product tower [C] bottom liquid, 8. MD2M product. DETAILED DESCRIPTION

[0028] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary illustrations and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope of protection that the present invention is intended to protect.

[0029] Unless otherwise stated, DUT-4, MOF-806 and PCN-223 used in the following examples are commercially available products or can be prepared by known methods.

[0030] Example 1 The modified adsorbent aluminum dihydrogen phosphate modified DUT-4 was prepared by the following method: DUT-4 was placed at 120°C for 4 h to remove moisture.

[0031] The dried DUT-4 was mixed with aluminum dihydrogen phosphate at a solid-liquid ratio (g:mL) of 1:60 and stirred for 12 h and then aged for 2 h. The material obtained after aging was sintered at 450° C. to obtain the aluminum dihydrogen phosphate modified DUT-4 adsorbent.

[0032] Example 2 The modified adsorbent dialkyl phosphate modified MOF-806 was prepared by the following method: MOF-806 was placed at 120°C to dry for 4 h to remove moisture.

[0033] The dried MOF-806 was mixed with dialkyl phosphate at a solid-to-liquid ratio (g:mL) of 1:50 and stirred for 12 h and then aged for 2 h. The material obtained after aging was sintered at 350° C. to obtain the dialkyl phosphate modified MOF-806 adsorbent.

[0034] Example 3 The modified adsorbent sodium hypophosphite modified PCN-223 was prepared by the following method: PCN-223 was placed at 120°C for 4 h to remove moisture.

[0035] The dried PCN-223 was mixed with sodium hypophosphite at a solid-to-liquid ratio (g:mL) of 1:60 and stirred for 12 h and then aged for 2 h. The material obtained after aging was sintered at 450° C. to obtain the sodium hypophosphite modified PCN-223 adsorbent.

[0036] Example 4 The proportions of the various components of the mixed methyl silicone oil raw material [1] are as follows: MM-11.34%, MDM-10.99%, MD2M-12.03%, MD3M-10.98%, D3-1.01%, D4-0.67%, D5-1.99%, D6-1.98%, MD4M and higher boiling point components are about 49.01%. 150kg / h of the mixed silicone oil raw material [1] is input into the de-weighting tower [A] for distillation. The tower top pressure of the de-weighting tower [A] is 8Kpa, the temperature is 150℃, and the reflux ratio is 1. 57.2kg / h of distillate [2] is obtained from the tower top and sent to the lightness removal tower [B]; 92.8kg / h of distillate [3] in the tower bottom is used as a high boiling point discharge device.

[0037] The top distillate [2] of the heavy removal tower [A] is 57.2 kg / h and enters the light removal tower [B] for separation. The top pressure of the light removal tower [B] is 20 Kpa, the temperature is 100 ° C, the reflux ratio is 5, and 18.5 kg / h of low-boiling substances such as MM and D3 [4] are removed from the top of the tower. 38.7 kg / h of materials [5] are taken out from the bottom of the tower and sent to the MDM product tower [C] for separation.

[0038] The top pressure of the MDM product tower [C] is 10Kpa, the temperature is 60°C, and the reflux ratio is 2.5. 16.1kg / h of ultra-low viscosity MDM finished product [6] is obtained from the top of the tower, wherein the contents of D3, D4, D5, and D6 are all less than 0.1% and the MDM content is greater than 99.9%. 22.6kg / h of material [7] in the bottom of the tower is sent to the D4 adsorption column [D].

[0039] 22.6 kg / h of the material [7] from the bottom of the MDM product tower [C] was introduced into a D4 adsorption column [D] filled with aluminum dihydrogen phosphate modified DUT-4 prepared in Example 1. The diameter of the D4 adsorption column [D] was 500 mm, the length was 3000 mm, the operating pressure was 0.2 MPa, and the operating temperature was 35°C. After adsorption, 21.5 kg / h of an ultra-low viscosity MD2M finished product [8] was obtained, wherein the contents of D3, D4, D5, and D6 were 0.011%, 0.014%, 0.021%, and 0.016%, respectively, and the MD2M content was greater than 99.9%.

[0040] The modified adsorbent after adsorption was regenerated by multiple cycles of vacuum-assisted hot nitrogen, and the same MDM product tower [C] bottom material in this example was adsorbed. The adsorption results are as follows:

[0041] As shown in the above data, aluminum dihydrogen phosphate modified DUT-4 can be regenerated multiple times by vacuum-assisted hot nitrogen, and the removal rate of D4 can still reach more than 95% after seven cycles.

[0042] Example 5 The proportions of the various components in the mixed methyl silicone oil raw material [1] are: MM-1.23%, MDM-9.08%, MD2M-34.46%, MD3M-15.98%, D3-2.01%, D4-1.54%, D5-9.63%, D6-3.13%, MD4M and higher boiling point components are approximately 22.94%.

[0043] 300 kg / h of mixed methyl silicone oil raw material [1] is fed into a de-weighting tower [A] for distillation. The tower top pressure of the de-weighting tower [A] is 20 KPa, the temperature is 150°C, and the reflux ratio is 1.5. 138.9 kg / h of distillate [2] is obtained from the tower top and is sent to a lightness removal tower [B]. 161.1 kg / h of distillate [3] in the tower bottom is used as a high boiling point discharge device.

[0044] The top distillate [2] of the de-heavy tower [A] is 161.1 kg / h and enters the light tower [B] for separation. The top pressure of the light tower [B] is 10 Kpa, the temperature is 100 ° C, the reflux ratio is 8.5, and 25.9 kg / h of low-boiling substances such as MM and D3 [4] are removed from the top of the tower. 135.2 kg / h of materials [5] are taken out from the bottom of the tower and sent to the MDM product tower [C] for separation.

[0045] The top pressure of the MDM product tower [C] is 10Kpa, the temperature is 60℃, and the reflux ratio is 2.5. 27.1kg / h of ultra-low viscosity MDM finished product [6] is obtained from the top of the tower, in which D3, D4, D5, and D6 are all less than 0.1% and the MDM content is greater than 99.5%. 108.1kg / h of material [7] in the bottom of the tower is sent to the D4 adsorption column [D].

[0046] 108.1 kg / h of the material [7] from the bottom of the MDM product tower [C] was introduced into a D4 adsorption column [D] filled with dialkyl phosphate modified MOF-806. The diameter of the D4 adsorption column [D] was 600 mm, the length was 3500 mm, the operating pressure was 0.4 MPa, and the operating temperature was 20°C. An ultra-low viscosity MD2M finished product of 103.4 kg / h [8] was obtained, wherein the contents of D3, D4, D5, and D6 were 0.013%, 0.015%, 0.0026%, and 0.007%, respectively, and the MD2M content was greater than 99.9%.

[0047] The modified adsorbent after adsorption was regenerated by multiple cycles of vacuum-assisted hot nitrogen, and the same MDM product tower [C] bottom material in this example was adsorbed. The adsorption results are as follows:

[0048] As shown in the above data, the dialkyl phosphate modified MOF-806 adsorbent can be regenerated multiple times by vacuum-assisted hot nitrogen, and the D4 absorption rate can still reach more than 95% after seven cycles.

[0049] Example 6 The proportions of the various components in the mixed methyl silicone oil raw material [1] are: MM-1.23%, MDM-9.08%, MD2M-34.46%, MD3M-15.98%, D3-2.01%, D4-1.54%, D5-9.63%, D6-3.13%, MD4M and higher boiling point components are approximately 22.94%.

[0050] 300 kg / h of mixed methyl silicone oil raw material [1] is fed into a de-weighting tower [A] for distillation. The tower top pressure of the de-weighting tower [A] is 20 KPa, the temperature is 150°C, and the reflux ratio is 1.5. 138.9 kg / h of distillate [2] is obtained from the tower top and is sent to a lightness removal tower [B]. 161.1 kg / h of distillate [3] in the tower bottom is used as a high boiling point discharge device.

[0051] The top distillate [2] of the de-heavy tower [A] is 161.1 kg / h and enters the light tower [B] for separation. The top pressure of the light tower [B] is 10 Kpa, the temperature is 100 ° C, the reflux ratio is 8.5, and 25.9 kg / h of low-boiling substances such as MM and D3 [4] are removed from the top of the tower. 135.2 kg / h of materials [5] are taken out from the bottom of the tower and sent to the MDM product tower [C] for separation.

[0052] The top pressure of the MDM product tower [C] is 10Kpa, the temperature is 60℃, and the reflux ratio is 2.5. 27.1kg / h of ultra-low viscosity MDM finished product [6] is obtained from the top of the tower, in which D3, D4, D5, and D6 are all less than 0.1% and the MDM content is greater than 99.5%. 108.1kg / h of material [7] in the bottom of the tower is sent to the D4 adsorption column [D].

[0053] 108.1 kg / h of the material [7] from the bottom of the MDM product tower [C] was passed into a D4 adsorption column [D] filled with sodium hypophosphite-modified PCN-223. The diameter of the D4 adsorption column [D] was 600 mm, the length was 3500 mm, the operating pressure was 0.4 MPa, and the operating temperature was 20°C. An ultra-low viscosity MD2M finished product of 103.4 kg / h was obtained, wherein the contents of D3, D4, D5, and D6 were 0.013%, 0.015%, 0.0026%, and 0.007%, respectively, and the MD2M content was greater than 99.9%.

[0054] The modified adsorbent after adsorption was regenerated by multiple cycles of vacuum-assisted hot nitrogen, and the same MDM product tower [C] bottom material in this example was adsorbed. The adsorption results are as follows:

[0055] As shown in the above data, the sodium hypophosphite modified PCN-223 adsorbent can be regenerated multiple times by vacuum-assisted hot nitrogen, and the absorption rate of D4 can still reach more than 95% after seven cycles.

[0056] In conjunction with specific embodiments 1-5, the present invention adopts distillation and adsorption synergistic separation technology to reduce the thermal contact time of the product, - reduce equipment cost and energy consumption, and obtain MDM and MD2M products with a single impurity content of less than 0.1% and a purity greater than 99.9%, which are higher in quality than the existing 99% purity products. In the two embodiments, although the composition of the raw materials is different, the method of the present invention also shows excellent purification effects through reasonable adjustment of operating parameters and process optimization, which proves the flexibility and versatility of the method of the present invention. Compared with existing production technologies, the present invention has higher purity, lower energy consumption and equipment cost, showing its significant advantages in the field of ultra-low viscosity methyl silicone oil purification.

[0057] Finally, it should be noted that the above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that the technical solutions described in the above-described embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A purification process for ultra-low viscosity octamethyltrisiloxane and decamethyltetrasiloxane, characterized in that: The following steps are involved: (1) Weight removal: The mixed methyl silicone oil raw material is input into a weight removal tower for separation, and the distillate from the top of the weight removal tower is sent to a light removal tower; (2) D3 removal: The top distillate of the heavy removal tower is sent to the light removal tower for separation. Low-boiling substances containing MM and D3 are removed from the top of the tower. The bottom liquid containing MDM, MD2M, and D4 components is obtained from the bottom of the tower and sent to the MDM product tower. (3) MDM purification: The bottom liquid of the light removal tower enters the MDM product tower for distillation, and an ultra-low viscosity MDM product is obtained from the top of the tower. The bottom liquid containing MD2M and D4 components is obtained from the bottom of the tower and sent to the D4 adsorption column; (4) D4 adsorption: The kettle liquid of the MDM product tower enters the D4 adsorption column for adsorption and removal of D4 to obtain an ultra-low viscosity MD2M product.

2. The process according to claim 1, characterized in that The methyl silicone oil raw material includes hexamethyldisiloxane MM, octamethyltrisiloxane MDM, decamethyltetrasiloxane MD2M, dodecamethylpentasiloxane MD3M and tetradecamethylhexasiloxane MD4M and impurities hexamethylcyclotrisiloxane D3, octamethylcyclotetrasiloxane D4, decamethylcyclopentasiloxane D5 and dodecamethylcyclohexasiloxane D6.

3. The process according to claim 1, characterized in that The operating conditions of the deweighting tower in the deweighting step are: pressure 7-15Kpa, temperature 150-200°C, and reflux ratio 0.5-5.

4. The process according to claim 1, characterized in that The operating conditions of the lightness removal tower in the D3 removal step are: pressure 15-25Kpa, temperature 100-150°C, and reflux ratio 1-10.

5. The process according to claim 1, characterized in that The operating conditions of the MDM product tower in the MDM purification step are: pressure 8-12Kpa, temperature 60-80°C, and reflux ratio 0.5-5.

6. The process according to claim 1, characterized in that The D4 adsorption column of the D4 adsorption step uses modified MOFs material as adsorbent.

7. The process according to claim 6, characterized in that The method for preparing the modified adsorbent is as follows: mixing the MOFs material and the phosphorylation agent in a certain proportion, stirring for 8-12 hours, and then aging for 1-2 hours; sintering the material obtained after aging at 300-450° C. to obtain the phosphoric acid modified adsorbent.

8. The process according to claim 7, characterized in that The phosphorylation agent is selected from any one of aluminum dihydrogen phosphate, dialkyl phosphate, ammonium dihydrogen phosphate, ammonium hydrogen phosphate, disodium hydrogen phosphate or sodium hypophosphite.

9. The process according to claim 1, characterized in that The operating conditions of the D4 adsorption step are: pressure 0.05-0.5 MPaG, temperature 20-60°C.

10. The process according to any one of claims 1 to 9, characterized in that The obtained ultra-low viscosity MDM is a colorless and odorless liquid with a viscosity of 0.1-2cst and a pH of 7.5-8.5; The ultra-low viscosity MD2M obtained is a colorless and odorless liquid with a viscosity of 0.5-3cst and a pH of 6-8.

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