A low molecular weight hydroxy silicone oil and preparation method thereof

Abstract

The present invention discloses a method for preparing low-molecular-weight hydroxy silicone oil, which relates to the technical field of preparation of hydroxy silicone oil. Dimethyldichlorosilane, a buffer solution, and desalted water are fully mixed in a tubular reactor, hydrolyzed, condensed, and dispersed into an oil-water mixture by a dispersion mill. The low-molecular-weight hydroxy silicone oil is then obtained after phase separation, degassing, and filter pressing. The product obtained by this method has stable quality, low cost, and a simple and efficient operation process.

Description

Technical Field

[0001] The present invention relates to the technical field of hydroxy silicone oil preparation, in particular to a low-molecular-weight hydroxy silicone oil and a preparation method thereof. Background Art

[0002] Low molecular weight hydroxy silicone oil, also known as small molecule hydroxy silicone oil, is an important silicone oil product. Its main uses include: as an intermediate to synthesize high molecular weight polymers; as a structure control agent to prepare silicone rubber such as heat-vulcanized silicone rubber and room temperature vulcanized silicone rubber; it can be used to prepare low molecular weight hydroxy silicone oil emulsions, which are used as finishing agents for fiber fabrics and additives for plastic products.

[0003] In the prior art, due to the high hydroxyl content in low-molecular-weight hydroxy silicone oils, it is difficult to achieve oil-water separation during the phase separation stage. Therefore, improvements are needed. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a method for preparing low molecular weight hydroxy silicone oil.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for preparing low molecular weight hydroxy silicone oil comprises the following steps: fully mixing dimethyldichlorosilane, a buffer solution and desalted water in a tubular reactor, performing hydrolysis, condensation and dispersion grinding to form an oil-water mixture, and then performing phase separation, degassing and filter pressing to obtain the low molecular weight hydroxy silicone oil.

[0007] Furthermore, the buffer solution is a mixed solution of NaOH and Na2CO3.

[0008] Furthermore, the purity of the dimethyldichlorosilane is ≥98%.

[0009] Furthermore, the added mass ratio of the dimethyldichlorosilane, buffer solution and desalted water is 1:3.5-4.0:6.5-7.5.

[0010] Furthermore, the rotation speed of the dispersion mill is 2450-2800 rpm.

[0011] Further, the following steps are included:

[0012] S1: Desalted water and buffer solution are pumped into the tee of the tubular reactor using a high-pressure pump, and dimethyldichlorosilane is pumped into the inner tube of the tee of the tubular reactor using a diaphragm air pump. The desalted water, buffer solution, and dimethyldichlorosilane enter the straight tube of the tubular reactor and react at 20-40°C. After the reaction, the mixture is fully mixed and dispersed in a dispersion mill to form an oil-water mixture.

[0013] S2: The oil-water mixture is collected and cooled in a cooler, then flows into a clarifier through the cooler outlet for phase separation. A nitrogen pipeline is laid at the bottom of the clarifier for uniform bubbling.

[0014] S3: In the clarifier, the upper light oil phase flows through the overflow port into the clarifier buffer tank to obtain crude silicone oil; the lower oil-water mixed phase is treated by the coalescing filter, the oil phase is condensed and circulated to the mixer, and the water phase is sent to the wastewater treatment system;

[0015] S4: The crude silicone oil in step S3 is preheated in a preheater and then enters a flash tank for degassing, and the condensed light components flow into a light component storage tank; the degassing silicone oil is filtered with activated carbon to obtain a qualified product.

[0016] Furthermore, in step S2, the cooler is cooled to 20-40°C.

[0017] Furthermore, in step S4, the preheating temperature of the preheater is 90-120° C., and the degassing pressure is 18-20 mbar.

[0018] The present invention also discloses a low-molecular-weight hydroxy silicone oil, which is prepared by any of the above preparation methods.

[0019] Furthermore, the content of silanol is 4.0-10 wt %, and the kinematic viscosity at 25° C. is 20-35 mm 2 / s.

[0020] The present invention has the beneficial effects of utilizing a tubular reactor in conjunction with a high-speed dispersing mill to continuously and quickly achieve the complete hydrolysis, polymerization, and neutralization of dimethylbenzene. Furthermore, the present invention utilizes a buffer solution prepared by mixing sodium hydroxide and sodium carbonate to carry out the reaction. During neutralization, the sodium carbonate and HCl in the buffer solution generate tiny CO2 bubbles, which, combined with nitrogen bubbling in the clarifier, produce flotation, achieving rapid oil-water phase separation. This solves the problem of difficulty in achieving oil-water separation during the phase separation stage in conventional methods due to the high hydroxyl content in low-molecular-weight hydroxy silicone oils. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a reaction flow chart of the present invention;

[0022] In the figure, 1-inner pipe, 2-straight pipe, 3-tee, 4-dispersion mill, 5-cooler, 6-clarifier, 7-coagulation filter, 8-clarifier buffer tank, 9-preheater, 10-flash tank, 11-light component storage tank. DETAILED DESCRIPTION

[0023] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it should not be understood as a limitation on the scope of protection of the present invention.

[0024] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0025] Reference Figure 1 , the technical solution of the present invention:

[0026] A method for preparing low molecular weight hydroxy silicone oil comprises the following steps: fully mixing dimethyldichlorosilane, a buffer solution and desalted water in a tubular reactor, performing hydrolysis, condensation and dispersion grinding to form an oil-water mixture, and then performing phase separation, degassing and filter pressing to obtain the low molecular weight hydroxy silicone oil.

[0027] The specific reaction equation is:

[0028] Dimethyl hydrolysis: (CH3)2SiCl2+2H2O→(CH3)2Si(OH)2+2HCl

[0029] Condensation: n(CH3)2Si(OH)2→HO-[-(CH3)2Si-O-] n -H (linear hydroxy silicone oil)

[0030] Neutralization: HCl + NaOH → H2O + NaCl; 2HCl + Na2CO3 → 2NaCl + H2O + CO2↑

[0031] As a preferred embodiment of the present invention, it may also have the following additional technical features:

[0032] The buffer solution is a mixed solution of NaOH and Na2CO3, wherein the concentration of NaOH is 15.5-16.5 wt% and the concentration of Na2CO3 is 4.5-5.5 wt%. The NaOH neutralizes the majority of the HCl produced during the hydrolysis process; the Na2CO3 neutralizes a small amount of HCl and maintains the system's pH at a weakly alkaline level. Under the action of the dispersing mill, the Na2CO3 reacts with the HCl to generate tiny CO2 bubbles, which, combined with N2 bubbling during the phase separation process, produce flotation, facilitating the rapid floating of the light oil.

[0033] The purity of the dimethyldichlorosilane is ≥98%.

[0034] The added mass ratio of the dimethyldichlorosilane, buffer solution and desalted water is 1:3.5-4.0:6.5-7.5.

[0035] The rotation speed of the dispersion mill is 2450-2800 rpm.

[0036] The following steps are involved:

[0037] S1: Desalted water and buffer solution are pumped into the tee 3 of the tubular reactor using a high-pressure pump, and dimethyldichlorosilane is simultaneously pumped into the inner tube 1 of the tee of the tubular reactor using a diaphragm air pump; the desalted water, buffer solution, and dimethyldichlorosilane enter the straight tube 2 of the tubular reactor and react at 20-40°C; after the reaction, they enter the dispersion mill 4 for thorough mixing and dispersion to form an oil-water mixture;

[0038] S2: The oil-water mixture is collected and cooled by cooler 5, and then flows into clarification tank 6 through the outlet of cooler 5 for phase separation. A nitrogen pipeline is laid at the bottom of clarification tank 6 for uniform bubbling;

[0039] S3: In the clarifier 6, the upper light oil phase flows through the overflow port into the clarifier buffer tank 8 to obtain crude silicone oil; the lower oil-water mixed phase is treated by the coalescing filter 7, the oil phase is condensed and circulated to the mixer, and the water phase is sent to the wastewater treatment system;

[0040] S4: The crude silicone oil in step S3 is preheated in the preheater 9 and then enters the flash tank 10 for degassing, and the condensed light components flow into the light component storage tank 11; the degassing silicone oil is filtered with activated carbon to obtain a qualified product.

[0041] The tubular reactor consists of a straight tube 2, a tee 3, and an inner tube 1. The straight tube 2 is connected to the tee 3, and the inner tube 1 is arranged inside the tee 3. The straight tube is 2000 mm long and has an inner diameter of 200 mm (the equipment refers to the patent CN201310516488.9 applied by the applicant);

[0042] In step S2, the cooler 5 is cooled to 20-40°C.

[0043] In step S4, the preheating temperature of the preheater 9 is 90-120° C., and the degassing pressure is 18-20 mbar.

[0044] A low molecular weight hydroxy silicone oil is prepared by any of the above preparation methods.

[0045] The content of silanol is 4.0-10%, and the kinematic viscosity at 25°C is 20-35 mm 2 / s.

[0046] The above technical solution is further described below with reference to specific embodiments.

[0047] The desalted water described in this article is distilled water.

[0048] The buffer solution is a mixed solution of NaOH and Na2CO3. The concentration of the solution is fixed and does not change with the embodiment. The concentration of NaOH is about 16wt% and the concentration of Na2CO3 is about 5wt%.

[0049] The purity of the dimethyldichlorosilane is 99%.

[0050] Example 1:

[0051] S1. Use a high-pressure pump to pump desalted water and buffer into the tee of the tubular reactor at a certain rate. At the same time, use a diaphragm air pump to pump dimethyldichlorosilane into the inner tube of the tee of the tubular reactor at a certain rate. The pumping ratio of dimethyldichlorosilane, buffer and desalted water is 1:4.0:6.5 (mass ratio). The desalted water, buffer and dimethyldichlorosilane enter the straight tube of the tubular reactor in a forward direction and react at 20°C. After the materials react in the straight tube of the tubular reactor, they enter the dispersion mill in a forward direction to be fully mixed and dispersed into droplet levels to form an oil-water mixture; the speed of the dispersion mill is 2450rpm;

[0052] S2. The oil-water mixture is collected and cooled to 25°C through a cooler. It then flows into a clarifier through the cooler outlet for phase separation. A N2 pipeline is laid at the bottom of the clarifier to bubble at a uniform speed to promote the floating of light oil.

[0053] In S3, the upper light oil phase in the clarifier flows through the overflow port into the clarifier buffer tank to produce crude silicone oil. The lower oil-water mixed phase is treated by a coalescing filter. The oil phase is then condensed and circulated to the mixer, while the water phase is sent to the wastewater treatment system.

[0054] S4. The crude silicone oil is preheated to 90°C in a preheater and then sent to a flash tank for degassing at a pressure of 18 mbar. The condensed light components flow into a light component storage tank and are regularly barreled. The degassing silicone oil is filtered with activated carbon to obtain qualified products.

[0055] Example 2:

[0056] S1. Use a high-pressure pump to pump desalted water and buffer into the tee of the tubular reactor at a certain rate. At the same time, use a diaphragm air pump to pump dimethyldichlorosilane into the inner tube of the tee of the tubular reactor at a certain rate. The pumping ratio of dimethyldichlorosilane, buffer and desalted water is 1:3.9:6.7 (mass ratio). The desalted water, buffer and dimethyldichlorosilane enter the straight tube of the tubular reactor in a forward direction and react at 25°C. After the materials react in the straight tube of the tubular reactor, they enter the dispersion mill in a forward direction to be fully mixed and dispersed into droplet levels to form an oil-water mixture; the speed of the dispersion mill is 2600rpm;

[0057] S2. The oil-water mixture is collected and cooled through a cooler, and then flows into a clarifier through the cooler outlet for phase separation. A N2 pipeline is laid at the bottom of the clarifier to bubble at a uniform speed to promote the floating of light oil.

[0058] In S3, the upper light oil phase in the clarifier flows through the overflow port into the clarifier buffer tank to produce crude silicone oil. The lower oil-water mixed phase is treated by a coalescing filter. The oil phase is then condensed and circulated to the mixer, while the water phase is sent to the wastewater treatment system.

[0059] S4. The crude silicone oil is preheated to 100°C in a preheater and then sent to a flash tank for degassing at a pressure of 19 mbar. The condensed light components flow into a light component storage tank and are regularly barreled. The degassing silicone oil is filtered with activated carbon to obtain qualified products.

[0060] Example 3:

[0061] S1. Use a high-pressure pump to pump desalted water and buffer into the tee of the tubular reactor at a certain rate. At the same time, use a diaphragm air pump to pump dimethyldichlorosilane into the inner tube of the tee of the tubular reactor at a certain rate. The pumping ratio of dimethyldichlorosilane, buffer and desalted water is 1:3.8:6.9 (mass ratio). The desalted water, buffer and dimethyldichlorosilane enter the straight tube of the tubular reactor in a forward direction and react at 30°C. After the materials react in the straight tube of the tubular reactor, they enter the dispersion mill in a forward direction to be fully mixed and dispersed into droplet levels to form an oil-water mixture; the speed of the dispersion mill is 2700rpm;

[0062] S2. The oil-water mixture is collected and cooled through a cooler, and then flows into a clarifier through the cooler outlet for phase separation. A N2 pipeline is laid at the bottom of the clarifier to bubble at a uniform speed to promote the floating of light oil.

[0063] In S3, the upper light oil phase in the clarifier flows through the overflow port into the clarifier buffer tank to produce crude silicone oil. The lower oil-water mixed phase is treated by a coalescing filter. The oil phase is then condensed and circulated to the mixer, while the water phase is sent to the wastewater treatment system.

[0064] S4. The crude silicone oil is preheated to 105°C in a preheater and then sent to a flash tank for degassing at a pressure of 20 mbar. The condensed light components flow into a light component storage tank and are regularly barreled. The degassing silicone oil is filtered with activated carbon to obtain qualified products.

[0065] Example 4:

[0066] S1. Use a high-pressure pump to pump desalted water and buffer into the tee of the tubular reactor at a certain rate. At the same time, use a diaphragm air pump to pump dimethyldichlorosilane into the inner tube of the tee of the tubular reactor at a certain rate. The pumping ratio of dimethyldichlorosilane, buffer and desalted water is 1:3.9:7.1 (mass ratio). The desalted water, buffer and dimethyldichlorosilane enter the straight tube of the tubular reactor in a forward direction and react at 35°C. After the materials react in the straight tube of the tubular reactor, they enter the dispersion mill in a forward direction to be fully mixed and dispersed into droplet levels to form an oil-water mixture; the speed of the dispersion mill is 2450rpm;

[0067] S2. The oil-water mixture is collected and cooled through a cooler, and then flows into a clarifier through the cooler outlet for phase separation. A N2 pipeline is laid at the bottom of the clarifier to bubble at a uniform speed to promote the floating of light oil.

[0068] In S3, the upper light oil phase in the clarifier flows through the overflow port into the clarifier buffer tank to produce crude silicone oil. The lower oil-water mixed phase is treated by a coalescing filter. The oil phase is then condensed and circulated to the mixer, while the water phase is sent to the wastewater treatment system.

[0069] S4. The crude silicone oil is preheated to 110°C in a preheater and then sent to a flash tank for degassing at a pressure of 18 mbar. The condensed light components flow into a light component storage tank and are regularly barreled. The degassing silicone oil is filtered with activated carbon to obtain qualified products.

[0070] Example 5:

[0071] S1. Use a high-pressure pump to pump desalted water and buffer into the tee of the tubular reactor at a certain rate. At the same time, use a diaphragm air pump to pump dimethyldichlorosilane into the inner tube of the tee of the tubular reactor at a certain rate. The pumping ratio of dimethyldichlorosilane, buffer and desalted water is 1:3.5:7.3 (mass ratio). The desalted water, buffer and dimethyldichlorosilane enter the straight tube of the tubular reactor in a forward direction and react at 40°C. After the materials react in the straight tube of the tubular reactor, they enter the dispersion mill in a forward direction to be fully mixed and dispersed into droplet levels to form an oil-water mixture; the speed of the dispersion mill is 2800rpm;

[0072] S2. The oil-water mixture is collected and cooled through a cooler, and then flows into a clarifier through the cooler outlet for phase separation. A N2 pipeline is laid at the bottom of the clarifier to bubble at a uniform speed to promote the floating of light oil.

[0073] In S3, the upper light oil phase in the clarifier flows through the overflow port into the clarifier buffer tank to produce crude silicone oil. The lower oil-water mixed phase is treated by a coalescing filter. The oil phase is then condensed and circulated to the mixer, while the water phase is sent to the wastewater treatment system.

[0074] S4. The crude silicone oil is preheated to 120°C in a preheater and then sent to a flash tank for degassing at a pressure of 19 mbar. The condensed light components flow into a light component storage tank and are regularly barreled for processing. The degassing silicone oil is filtered with activated carbon to obtain qualified products.

[0075] Comparative Example 1

[0076] In step S1, the pumping ratio of dimethyldichlorosilane, buffer solution and desalted water is 1:3.3:6.5 (mass ratio). The desalted water, buffer solution and dimethyldichlorosilane flow into the straight tube of the tubular reactor in a forward direction and react at 20°C. Other steps are the same as in Example 1.

[0077] Comparative Example 2

[0078] In step S1, the pumping ratio of dimethyldichlorosilane, buffer solution and desalted water is 1:4.0:6.5 (mass ratio). The desalted water, buffer solution and dimethyldichlorosilane flow into the straight tube of the tubular reactor in a forward direction and react at 45°C. Other steps are the same as in Example 1.

[0079] Comparative Example 3

[0080] In step S1, the buffer solution contains only 15.5 wt% NaOH solution, and N2 bubbling is not performed during phase separation in the clarifier. Other procedures are the same as those in Example 1.

[0081] The above examples and comparative examples were subjected to performance tests, and the viscosity and hydroxyl content of the silicone oil after the tabs were placed at 25°C for 7 days were tested. The test results are shown in the following table:

[0082]

[0083] As can be seen from the above table, the silicone oil produced in the embodiment has little change in viscosity and hydroxyl content after being placed for 7 days, while the viscosity of the silicone oil produced in Comparative Examples 1 and 2 is very large, the hydroxyl content is small, and the data of the two after 7 days vary greatly. The main reason may be that the pumping ratio of dimethyldichlorosilane, buffer and desalted water in Comparative Example 1 is 1:3.3:6.5, and the amount of buffer added is on the small side, which cannot completely neutralize the HCl produced in the hydrolysis reaction. The residual HCl will promote the dehydration condensation of silanols, thereby making the viscosity of the prepared hydroxy silicone oil larger and unstable (viscosity gradually increases during storage); the straight tube temperature of the tubular reactor in Comparative Example 2 is controlled at 45 ° C, and the temperature is slightly higher, which promotes further condensation of some silanols, thereby causing the viscosity of the hydroxy silicone oil to be slightly larger. But at the same time, in Comparative Example 2, the amount of buffer given is sufficient, and the HCl produced by hydrolysis is basically completely neutralized, so it is more stable to store. However, Comparative Example 3 is difficult to produce continuously, mainly because: the buffer solution is only sodium hydroxide, without sodium bicarbonate, and no N2 bubbling is provided in the later stage to assist phase separation. The oil-water mixture produced after the rapid dispersion reaction of the dispersion mill has a high hydroxyl content in the oil phase, and the time required for phase separation by natural standing is extremely long, so continuous production cannot be carried out.

[0084] Under the premise that no conflict occurs, those skilled in the art may freely combine and superimpose the above-mentioned additional technical features.

[0085] The above descriptions are merely preferred embodiments of the present invention. Any technical solution that achieves the purpose of the present invention by substantially the same means shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing low molecular weight hydroxy silicone oil, characterized in that, Dimethyldichlorosilane, buffer solution and desalted water are fully mixed in a tubular reactor, and then dispersed into an oil-water mixture through hydrolysis, condensation and dispersion milling, and then phase separation, degassing and filter pressing to obtain low molecular weight hydroxy silicone oil; The buffer solution is a mixed solution of NaOH and Na2CO3; wherein the concentration of NaOH is 15.5-16.5 wt%, and the concentration of Na2CO3 is 4.5-5.5 wt%; The added mass ratio of the dimethyldichlorosilane, buffer and desalted water is 1: 3.5~4.0: 6.5~7.5; The following steps are involved: S1: Use a high-pressure pump to pump desalted water and buffer solution into the tee (3) of the tubular reactor, and use a diaphragm air pump to pump dimethyldichlorosilane into the inner tube (1) of the tee of the tubular reactor; the desalted water, buffer solution and dimethyldichlorosilane enter the straight tube (2) of the tubular reactor and react at 20-40°C; after the reaction, they enter the dispersion mill (4) for thorough mixing and dispersion to form an oil-water mixture; S2: The oil-water mixture is collected and cooled through a cooler (5), and then flows through the outlet of the cooler (5) into a clarification tank (6) for phase separation. A N2 pipeline is laid at the bottom of the clarification tank (6) for uniform bubbling; S3: In the clarifier (6), the upper light oil phase enters the clarifier buffer tank (8) through the overflow port to obtain crude silicone oil; the oil-water mixed phase in the lower layer is treated by the coalescing filter (7), the oil phase is condensed and circulated to the mixer, and the water phase is sent to the wastewater treatment system; S4: The crude silicone oil in step S3 is preheated in a preheater (9) and then enters a flash tank (10) for degassing. The condensed light components flow into a light component storage tank (11). The degassing silicone oil is filtered with activated carbon to obtain a qualified product.

2. The method for preparing a low molecular weight hydroxy silicone oil according to claim 1, wherein The purity of the dimethyldichlorosilane is ≥98%.

3. The method for preparing a low molecular weight hydroxy silicone oil according to claim 1, wherein The rotation speed of the dispersion mill is 2450~2800 rpm.

4. The method for preparing a low molecular weight hydroxy silicone oil according to claim 1, wherein In step S2, the cooler (5) is cooled to 20-40°C.

5. The method for preparing a low molecular weight hydroxy silicone oil according to claim 1, wherein In step S4, the preheating temperature of the preheater (9) is 90-120°C, and the degassing pressure is 18-20 mbar.

6. A low molecular weight hydroxy silicone oil, characterized in that The method is as described in any one of claims 1 to 5.

7. The low molecular weight hydroxy silicone oil according to claim 6, characterized in that The silanol content is 4.0~10wt%, and the kinematic viscosity at 25℃ is 20~35 mm 2 / s.

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