Method for producing linear organosilicon

Abstract

The present invention relates to a method for producing a low-volatile organosilicon linear product. The method comprises removing chloride ions from a hydrolyzate of dimethyldichlorosilane and reducing the volatile content at 180-280°C and -0.0955--0.0998 MPa. The obtained organosilicon linear product has a volatile content of less than 0.5% and a viscosity of 50-150 mm. 2 / s, chloride ion content is less than 1 ppm. The preparation method can be widely applied to the preparation of organosilicon subsequent products such as low cyclic content 107 adhesive, low cyclic content amino silicone oil, low cyclic content methyl silicone oil and low cyclic content vinyl silicone oil, and can meet the requirements of the European Union on the content limit of cyclics in polymers.

Description

Technical Field

[0001] This application claims the priority of a prior application (the invention name is "Method for Producing Organic Silicon Linear Body", patent application number 202110387311.8) filed with the CNIPA on April 9, 2021. The full text of the prior application is incorporated into this application by reference.

[0002] The present invention relates to the field of synthesis of organic silicon compounds. In particular, it relates to a method for producing an organic silicon linear body, which pretreats the hydrolysis product of dimethyldichlorosilane, removes low molecules, and obtains an organic silicon cyclic body and an organic silicon linear body with a chloride ion content of less than 1 ppm and a volatile substance content of less than 0.5%.

Background Art

[0003] The hydrolysis product of dimethyldichlorosilane is composed of 20% - 80% linear siloxane (linear body) and 80% - 20% cyclic siloxane (cyclic body). Conventional processes for treating the hydrolysis product are cracking technologies such as Chinese Patent Application Publication Nos. CN101148455A, CN104119372A, and CN104497035A. Among them, Chinese Patent Application Publication No. CN101148455A discloses that the chains of the linear body and cyclic body of the hydrolysis product are ring-opened before reforming into a ring again to generate a cyclic body under basic catalyst conditions. During the cracking reaction, it is necessary to discharge residues once a week, and this process has the disadvantages of high unit consumption of the hydrolysis product and high energy consumption. Furthermore, when producing downstream products using conventional cracking product DMC (cyclic siloxane mixture), ring-opening polymerization is dominant. This reaction is an equilibrium reaction, and 15% of low-boiling substances are generated, but the recycling of low-boiling substances is relatively energy-wasteful. More importantly, downstream products produced from DMC contain a large amount of volatile substances, so it is difficult to meet the requirement that the D4, D5, and D6 content indices for polymers in the European Union are less than 0.01%.

Summary of the Invention

[0004] On the one hand, Chinese patents CN104031084B, CN105175730B, and CN106083910B all propose separating the hydrolyzate into cyclic and linear forms and using the obtained cyclic and linear forms in the production of 110 rubber and 107 rubber respectively. In Chinese patent CN106083910B, a one-stage flash evaporation method is used under vacuum (-80 to -95 KPa) to remove low-molecular substances, and the temperature for low-molecular substance removal is strictly controlled at 120 to 150 °C. In claim 4 of this patent, the linear-form content in the separated linear form is defined as 85 to 99%. However, according to the data in the examples, when the separation temperature is controlled at 130 to 135 °C, the linear-form content is 90% to 93% and does not reach 98% or more. This is also confirmed by Chinese patent CN104031084B. From the results of Examples 1 to 3, when two-stage low-molecular substance removal is used to separate the cyclic and linear forms under a vacuum of -0.097 MPa, the content of the linear form obtained by separation varies between 75% and 98% by changing the separation temperature between 100 and 200 °C. To achieve a high linear-form yield, it is necessary to strictly control the temperature for low-molecular substance removal at 140 to 160 °C. This is because when the temperature for low-molecular substance removal exceeds 150 °C, the content of the separated linear form decreases instead, and only when the temperature is controlled at 150 °C can a linear-form product with a maximum content of 98% be obtained. Thus, in Chinese patent CN105175730B, where low-molecular substance removal is carried out at a lower temperature, in fact, the content of impurities in the linear form (mainly low-molecular substances, generally called "low-boiling substances" in this field) is very high, and the content of the linear form should not exceed 98%.

[0005] Therefore, the prior art solutions for treating the hydrolysis product of dimethyldichlorosilane cannot reduce the volatile content in the linear product to less than 1%, that is, they cannot solve the problem of high content of low volatiles. Octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecylmethylcyclohexasiloxane (D6) have been newly added to the SVHC (the content used in cosmetics and personal care products, polishing and waxing, cleaning and cleansing products, textile processing products, and dyes is a requirement) of the REACH regulation of the European Union and must be less than 0.01%.

[0006] In the industry, there is a need for a new method for treating the hydrolysis product of dimethyldichlorosilane and a new method for obtaining a satisfactory linear product.

[0007] The inventors of the present invention have found through research that by controlling the impurities, especially the chlorine content, in the hydrolysis product of dimethyldichlorosilane, it not only helps to improve the operating conditions during the downstream separation of the cyclic and linear forms, avoid the decomposition and reaction of the linear form during the separation operation, but also enables the hydrolysis product to be adapted to more advanced separation conditions, providing a route for reducing the content of low volatiles in the separated linear form. Thus, the present invention has been completed.

[0008] The present invention relates to a method for producing an organosilicon linear product, comprising: S1: a step of pretreating the hydrolysis product of dimethyldichlorosilane so that the chloride ion content in the pretreated hydrolysis product is 1 ppm or less; S2: a step of removing low-molecular substances from the hydrolysis product obtained in the pretreatment of step S1 under reduced pressure to separate an organosilicon cyclic form and an organosilicon linear form, wherein the removal of low-molecular substances under reduced pressure is carried out at a temperature of 180 to 280 °C and a pressure of ≤ -0.0955 MPa; A manufacturing method characterized by including the above steps is provided.

[0009] The hydrolysis product of dimethyldichlorosilane is derived from the upstream process and has a meaning generally known in the art. It mainly contains 80-20% linear siloxane, 20-80% cyclic bodies (including octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), etc.), and trace impurities. The main impurities include water, chloride ions, and hydrocarbons.

[0010] According to the present invention, the pretreatment in step S1 can use various separation methods known in the art for removing impurities, including but not limited to filtration, adsorption, etc. For example, filtration by a filter, activated carbon adsorption, molecular sieve, and resin adsorption can be mentioned. The activated carbon, molecular sieve, and resin can be the activated carbon, molecular sieve, and resin generally used in the art for adsorbing or filtering impurities such as chloride ions, for example, D201 resin, D301 resin, etc. To improve the removal result of chloride ions, a plurality of separation methods can be used in combination. For example, activated carbon, molecular sieve adsorption, and resin adsorption can be used in combination. As another example, a method for removing large-particle impurities and a method for removing low-molecular substances can be used in combination.

[0011] In some embodiments of the present invention, the hydrolysis product of dimethyldichlorosilane is fed into the pretreatment device of step S1 at a flow rate of 3-15 m 3 / h, preferably at a flow rate of 7-15 m 3 / h.

[0012] In one embodiment of the present invention, first, a primary prefilter is used to remove mechanical impurities and colloids from the hydrolysis product, and then a secondary treatment is performed using an activated carbon filter, molecular sieve, and / or resin to adsorb impurities of low-molecular substances containing chloride ions. In the secondary treatment, any one of the activated carbon filter, molecular sieve, and resin can be selected, or two of them can be used in combination, or all three can be used in combination. In a specific embodiment of the present invention, the secondary treatment uses resin.

[0013] In a preferred embodiment of the present invention, a backflush system is simultaneously provided in the pretreatment apparatus in order to improve the impurity removal result of the pretreatment.

[0014] According to the present invention, the chloride ion content in the hydrolyzate is controlled to be less than 1 ppm, preferably less than 0.5 ppm.

[0015] According to the study by the present inventors, the physical properties of the linear product obtained by separating from the hydrolyzate of dimethyldichlorosilane with a chloride ion content of 3 ppm or more are unstable, and it undergoes a condensation reaction by itself, resulting in an increase in viscosity, an increase in the volatilization amount, an increase in turbidity, and it has been found that the product is not satisfactory. It is very difficult to subject the obtained linear product to a chlorine removal treatment to obtain a satisfactory product, and it is also very difficult to reduce the content of low-volatile substances contained therein. In Chinese Patent CN104031084B, the possibility that the isolated linear product undergoes side reactions can only be reduced by controlling the low-molecular-weight removal temperature of the crude linear product to a lower temperature (140 to 160°C). This is also the reason why the content of the linear product obtained after low-molecular-weight removal at 200°C in Example 3 of the same patent decreased to 82%, which is significantly lower than the content of the linear product obtained at 150°C in Example 2, which was 98%. According to the study by the present inventors, before separating the cyclic and linear products from the hydrolyzate of dimethyldichlorosilane, when the chlorine content in the hydrolyzate is reduced to 1 ppm or less, particularly 0.5 ppm or less, it has been found that the impurities in the obtained linear product are low, the linear product itself is stable, and it does not undergo a condensation reaction. Furthermore, since such a hydrolyzate can withstand a higher low-molecular-weight removal temperature, the separation of the cyclic and linear products can be carried out at a higher temperature, the separation efficiency of the linear product is significantly improved, and particularly the content of low-volatile substances is significantly reduced.

[0016] According to the present invention, in order to improve the utilization of energy in the entire method process, a step S11 of preheating the pretreated hydrolyzate can be added to step S1 and step S2. Specifically, the pretreated hydrolyzate obtained in step S1 is first preheated in a heat exchange device using the annular body and / or linear body separated in step S2 as a heat source. In one embodiment of the present invention, the heat exchange device is an economizer.

[0017] According to the present invention, in step S2, before the pretreated hydrolyzate is introduced into the low-molecular-weight removal device and undergoes low-molecular-weight removal under reduced pressure, a preheating device may be used to heat the pretreated hydrolyzate to the temperature required for low-molecular-weight removal under reduced pressure. In one embodiment of the present invention, the hydrolyzate is heated to 180 to 280 °C, preferably 190 to 280 °C, more preferably 200 to 280 °C.

[0018] According to the present invention, the low-molecular-weight removal under reduced pressure in step S2 is preferably carried out at a temperature of 190 to 280 °C, more preferably 220 to 280 °C.

[0019] According to the present invention, the low-molecular-weight removal under reduced pressure in step S2 can be carried out under reduced pressure, and a device generally used in the art can be used. As such a device, for example, as long as it is a device that can achieve a uniform distribution of the hydrolyzate due to its structural configuration or packing distribution, a flash evaporation device, a packed column, a falling film evaporation device, etc. can be used, but it is not limited thereto. The reduced-pressure low-molecular-weight removal device may be a single reduced-pressure low-molecular-weight removal device or a series of a plurality of reduced-pressure low-molecular-weight removal devices connected in cascade. That is, the low-molecular-weight removal under reduced pressure may be carried out in one stage, or may be carried out in a plurality of stages (two or more stages) under reduced pressure.

[0020] In some embodiments of the present invention, in step S2, the removal of low-molecular-weight substances under reduced pressure is carried out in two stages; the first stage of the removal of low-molecular-weight substances under reduced pressure has a temperature range of 180 to 280 °C, preferably 200 to 280 °C, more preferably 220 to 280 °C and a pressure ≤ -0.0955 MPa, and the second stage of the removal of low-molecular-weight substances under reduced pressure has a temperature range of 190 to 280 °C, preferably 220 to 280 °C, more preferably 240 to 280 °C and a pressure ≤ -0.0955 MPa. The temperature of the second stage of the removal of low-molecular-weight substances under reduced pressure is higher than the temperature of the first stage of the removal of low-molecular-weight substances under reduced pressure. The cyclic bodies D4, cyclic bodies D5, etc. obtained by the first-stage removal of low-molecular-weight substances under reduced pressure are discharged from the upper part of the first-stage reduced-pressure low-molecular-weight substance removal device, enter the condenser at the upper part of the device, and are collected after condensation. The linear bodies obtained by the first-stage removal of low-molecular-weight substances under reduced pressure are discharged from the bottom of the first-stage reduced-pressure low-molecular-weight substance removal device in a liquid state, enter the second-stage reduced-pressure low-molecular-weight substance removal device, and have low-molecular-weight substances removed under reduced pressure. The cyclic bodies and short linear bodies obtained by the second-stage removal of low-molecular-weight substances under reduced pressure are discharged from the upper part of the second-stage reduced-pressure low-molecular-weight substance removal device, enter the condenser at the upper part of the device, and are collected after condensation. The liquid linear bodies obtained by the second-stage removal of low-molecular-weight substances under reduced pressure are discharged. The cyclic bodies obtained by the first-stage removal of low-molecular-weight substances under reduced pressure, and the cyclic bodies and short linear bodies obtained by the second-stage removal of low-molecular-weight substances under reduced pressure may be combined and collected in a storage device using the same set of aggregators. Alternatively, they may be individually collected in corresponding independent storage devices using independent condensers.

[0021] In one embodiment of the present invention, in step S2, a flash evaporation device and a vertical falling-film evaporation device connected in series are used to perform low-molecular-weight removal under reduced pressure. Flash evaporation has a temperature range of 180°C to 280°C, preferably 200 to 280°C, more preferably 220 to 280°C. Falling-film evaporation has a temperature range of 190 to 280°C, preferably 220 to 280°C, more preferably 240 to 280°C, and the temperature of falling-film evaporation is higher than that of flash evaporation. The hydrolyzate of dimethyldichlorosilane preheated to 180 to 280°C is sent to the flash evaporation device, and a flash evaporation separation operation is performed under the condition of -0.0955 MPa or less. Part of the cyclic body D4 and the cyclic body D5 evaporates and is discharged from the upper part of the flash evaporation device, enters the condenser at the upper part of the flash evaporation device, and is condensed and collected. Most of the linear bodies are in a liquid phase state and are discharged from the bottom of the flash evaporation device. The base liquid of the flash evaporation device enters the vertical falling-film evaporation device. Under the conditions of 190 to 280°C and -0.0955 MPa or less, light components including cyclic bodies and short linear bodies in the base liquid evaporate, and the linear bodies of the heavy components remain in a liquid state. These simultaneously enter the gas-liquid separation space at the bottom of the falling-film evaporation device. The light component gas enters the condenser at the upper part of the flash evaporation device under vacuum, and is condensed and collected after condensation. The liquid of the linear bodies of the heavy components is discharged. In one embodiment of the present invention, the liquid of the linear bodies of the heavy components is sent to the economizer by a linear body discharge pump, exchanges heat with the pretreated hydrolyzate, and then is cooled by a linear body cooling device and sent to a linear body storage device. In the above embodiment, the cyclic bodies obtained by flash evaporation and the cyclic bodies and short linear bodies obtained by falling-film evaporation may be combined and collected in the storage device, or may be separately collected in corresponding independent storage devices.

[0022] The vertical falling-film evaporator is a more preferred reduced-pressure low-molecular-weight removal device because it helps to evenly distribute the material.

[0023] In the present invention, the annular bodies and short straight-chain bodies collected in step S2 may be used in other processes. The process is not limited, but includes a process of manufacturing a product using the annular body as a raw material, and a process of further separating the annular body to obtain an annular body with less variation in composition.

[0024] In one embodiment of the present invention, the annular bodies and short straight-chain bodies obtained in step S2 are condensed in a condenser at the upper part of the low-molecular-weight removing device, then enter the processing device, are pumped out by a pump, and after water is removed, they are sent to a storage device for annular bodies and short straight-chain bodies for use in the next process step. The above-described processing method for annular bodies and short straight-chain bodies is suitable for combined annular bodies and short straight-chain bodies, but is also suitable for non-combined annular bodies and non-combined annular bodies and short straight-chain bodies.

[0025] The low-molecular-weight removing device operates under vacuum conditions. In one embodiment of the present invention, a vacuum duct connected to a vacuum pump is installed at the upper part of the condenser to evacuate the entire system of the low-molecular-weight removing device.

[0026] According to the present invention, when the content of low-volatile components in the linear body product obtained by removing low-molecular-weight components in step S2 does not meet the process requirements (when the content of low-volatile components exceeds 0.5%), the raw material return pipeline is used to repeat step S2 until the content of low-volatile substances in the product is less than 0.5%, and then it is discharged.

[0027] In the present invention, the linear body isolated in step S2 is cooled to 20 - 50°C and collected.

[0028] The present invention further provides a manufacturing apparatus for the above-described method for manufacturing an organic silicon linear body. According to the present invention, the apparatus includes a pretreatment device for a hydrolyzate of dimethyldichlorosilane and a vacuum low-molecular-weight removing device.

[0029] In one embodiment of the present invention, the pretreatment device includes a primary prefilter and a secondary treatment device; the primary prefilter removes mechanical impurities and colloids by filtration, and the secondary treatment device is an activated carbon filter, a molecular sieve, and / or a resin.

[0030] In some embodiments of the present invention, the vacuum low-molecular removal device includes two stages of vacuum low-molecular removal devices connected in series. In one embodiment of the present invention, in the two-stage vacuum low-molecular removal device connected in series, the first-stage vacuum low-molecular removal device is a flash evaporation device, and the second-stage vacuum low-molecular removal device is a falling-film evaporation device.

[0031] According to the present invention, a preheating device is installed between the pretreatment device and the vacuum low-molecular removal device.

[0032] According to the present invention, a heat exchange device is installed between the pretreatment device and the preheating device, and the heat exchange device is connected to the gas outlet and / or the liquid outlet of the vacuum low-molecular removal device. When the heat exchange device is connected to the gas outlet or the liquid outlet of the vacuum low-molecular removal device, the heat exchange device has a series of ducts for passing gas or liquid. When the heat exchange device is connected to the gas outlet and the liquid outlet of the vacuum low-molecular removal device, the heat exchange device has two independent sets of ducts for passing gas and liquid respectively.

[0033] According to the present invention, when the gas outlet of the vacuum low-molecular removal device is not connected to the heat exchange device, a condenser is connected immediately downstream thereof. When the gas outlet of the vacuum low-molecular removal device is connected to the heat exchange device, the condenser is connected downstream of the gas discharge outlet of the heat exchange device. Based on the present invention, those skilled in the art will understand that the gas outlet of the vacuum low-molecular removal device may be the gas outlet of all the vacuum low-molecular removal devices in the vacuum low-molecular removal device, or the gas outlet of any one or more vacuum low-molecular removal devices.

[0034] According to the present invention, the condenser is connected to the annular body treatment device.

[0035] According to the present invention, the annular body processing device is connected to the annular body storage device.

[0036] According to the present invention, when the liquid outlet of the decompression low-molecular-weight removal device is not connected to the heat exchange device, a cooling device is connected immediately downstream of the liquid outlet. When the liquid outlet of the decompression low-molecular-weight removal device is connected to the heat exchange device, the cooling device is connected downstream of the liquid discharge outlet of the heat exchange device. Based on the present invention, those skilled in the art will understand that, from the perspective of the operating conditions of low-molecular-weight removal under reduced pressure, the liquid outlet of the decompression low-molecular-weight removal device is the liquid outlet of the final-stage decompression low-molecular-weight removal device in the decompression low-molecular-weight removal device.

[0037] According to the present invention, the cooling device is connected to the linear body storage device.

[0038] In a preferred embodiment of the present invention, the manufacturing apparatus for the method of manufacturing the above-mentioned organic silicon linear body includes a pretreatment apparatus for the hydrolyzate of dimethyldichlorosilane and a vacuum low-molecular weight removal apparatus. The pretreatment apparatus includes a primary prefilter and a secondary treatment apparatus. The primary prefilter removes mechanical impurities and colloids by filtration, and the secondary treatment apparatus is an activated carbon filter, a molecular sieve, and / or a resin. The vacuum low-molecular weight removal apparatus is a flash evaporation apparatus and a falling-film evaporation apparatus connected in series. A preheating apparatus is installed between the pretreatment apparatus and the vacuum low-molecular weight removal apparatus. A heat exchange apparatus is installed between the pretreatment apparatus and the preheating apparatus, and the heat exchange apparatus is connected to the gas outlet and / or the liquid outlet of the vacuum low-molecular weight removal apparatus. When the gas outlet of the vacuum low-molecular weight removal apparatus is connected to the heat exchange apparatus, a condenser is connected downstream of the gas discharge outlet of the heat exchange apparatus. When the gas outlet of the vacuum low-molecular weight removal apparatus is not connected to the heat exchange apparatus, a condenser is connected immediately downstream of the gas outlet. When the liquid outlet of the vacuum low-molecular weight removal apparatus (falling-film evaporation apparatus) is connected to the heat exchange apparatus, a cooling apparatus is connected downstream of the liquid discharge outlet of the heat exchange apparatus. When the liquid outlet of the vacuum low-molecular weight removal apparatus (falling-film evaporation apparatus) is not connected to the heat exchange apparatus, a cooling apparatus is connected immediately downstream of the liquid outlet. The condenser is connected to an annular body treatment apparatus. The annular body treatment apparatus is connected to an annular body storage apparatus. The cooling apparatus is connected to a linear body storage apparatus.

[0039] The organic silicon linear body obtained by the method of the present invention has a viscosity of 50 to 120 mm 2 / s, a volatile content of less than 0.5%, and a chloride ion content of less than 1 ppm. The linear body can be widely used in the production of organic silicon downstream products such as 107 adhesives with a low cyclic content, amino silicone oils with a low cyclic content, methyl silicone oils with a low cyclic content, and vinyl silicone oils with a low cyclic content. When using the linear body product to produce downstream products, low-boiling substances are not generated according to the condensation reaction principle, and the volatile content of the downstream products is low, so it can meet the requirements for products with a low volatile content.

[0040] The linear body referred to in the present invention is a mixture of hydroxy-terminated linear dimethylpolysiloxane with a normal molecular weight distribution, which can be used as a starting material for downstream organic silicon products, and has advantages such as a short polymerization time and a low content of volatile substances.

Brief Description of the Drawings

[0041]

Figure 1

Modes for Carrying Out the Invention

[0042] Hereinafter, the present invention will be further described with reference to examples. It should be noted that the examples cannot be used to limit the protection scope of the present invention. Those skilled in the art will understand that any improvements and changes made based on the present invention are included in its protection scope.

[0043] All the conventional chemical reagents used in the following examples are commercially available.

[0044] The devices and processes used in the examples are as follows. The hydrolyzate tank is connected to the pretreatment device. The pretreatment device is connected to the economizer. The inlet of the heat exchange pipeline of the economizer is connected to the bottom outlet of the falling-film evaporator, the outlet of the heat exchange pipeline of the economizer is connected to the cooler, the cooler is connected to the straight-chain tank, and the outlet of the economizer is connected to the preheater. The preheater is connected to the supply port of the flash evaporation tank. A condenser is connected to the upper part of the flash evaporation tank. The condenser is separately connected to the treatment tank and the vacuum pump. The treatment tank is connected to the annular tank. The bottom outlet of the flash evaporation tank is connected to the falling-film evaporator. The upper part of the gas-liquid separation space at the bottom of the falling-film evaporator is connected to the condenser. The hydrolyzate of dimethyldichlorosilane from the upstream process is stored in the hydrolyzate tank and sent to the pretreatment device via a pipeline for pretreatment to reduce the chloride ion content. The pretreated hydrolyzate is sent to the economizer via a pipeline and preheated by exchanging heat with the straight-chain body discharged from the bottom of the falling-film evaporator. The preheated hydrolyzate is sent to the preheater via a pipeline, heated to the flash evaporation temperature there, and then sent to the flash evaporation tank. The cyclic body in the hydrolyzate evaporates in the flash evaporation tank, is discharged from the upper part of the flash evaporation tank, condensed in the condenser, and collected in the treatment tank. The straight-chain body in the hydrolyzate remains liquid in the flash evaporation tank, is discharged from the bottom of the flash evaporation tank, and sent to the falling-film evaporator. After removing low-molecular substances under reduced pressure, the cyclic body and the short straight-chain body therein evaporate, are discharged from the upper part of the gas-liquid separation space at the bottom of the falling-film evaporator, condensed in the condenser, and collected in the treatment tank. The liquid straight-chain body is discharged from the bottom of the falling-film evaporator, sent to the economizer to exchange heat with the pretreated hydrolyzate, then sent to the cooler to be cooled, and collected in the straight-chain tank. The cyclic body and the short straight-chain body in the treatment tank are sent to the annular tank for storage.

Example

[0045] Example 1: (1) Pretreatment and heating of the hydrolyzate of dimethyldichlorosilane Flow rate of 8 m³ / h from upstream 3 The hydrolysis product of dimethyldichlorosilane with a flow rate of 8 m³ / h from upstream mainly contains 60% linear siloxane, 27% octamethylcyclotetrasiloxane (D4), 8% decamethylcyclopentasiloxane (D5), 3% D6, 1% D7 and other trace impurities. The impurities include water, chloride ions and hydrocarbons. The primary pre-filter is used to remove mechanical impurities and colloids from the hydrolysis product, and the D201 resin is used for secondary treatment. The chloride ion content in the hydrolyzate after filtration treatment was 1 ppm. The pretreated hydrolysis product is sent to a linear / cyclic separation raw material storage tank and then sent to an economizer by a flash evaporation supply pump. The hydrolysis product exchanges heat with the high-temperature linear product in the economizer and is then heated to 220 °C in a preheater.

[0046] (2) Flash evaporation of the hydrolysis product under reduced pressure The hydrolysis product is sent to a flash evaporation tank and separated by flash evaporation under a negative pressure of -0.098 MPa. A part of the cyclic D4 and cyclic D5 evaporates and is discharged from the upper part of the flash evaporation tank. Most of the linear form becomes a liquid phase and is discharged from the bottom of the flash evaporation tank.

[0047] (3) Cooling and treatment of the cyclic form After the cyclic form enters the vapor-phase pipe of the flash evaporation tank, it is condensed in the condenser at the top of the tower and flows into the treatment tank. The cyclic form is pumped out by a pump and sent to a cyclic form tank for use in the next process step.

[0048] (4) Falling-film evaporation and cooling of the linear form A small amount of the cyclic form is mixed in the linear form discharged from the bottom of the flash evaporation tank, and it is further treated at -0.098 MPa and a temperature of 240 °C by falling-film evaporation to obtain the linear form. It is sent to the economizer by a discharge pump, exchanges heat with the pretreated hydrolysis product, is cooled to room temperature in a cooler, and then sent to a product storage tank.

[0049] The linear product obtained in Example 1 has the following structural formula, and the molecular weight has a normal distribution of 4000 - 7000. Refer to Table 1 for test data.

Chemical Formula

[0050] Example 2: The operation steps and related parameters of Example 2 are the same as those of Example 1, except that the flash evaporation temperature in Example 2 is 180 °C and the falling film evaporation temperature is 200 °C. Refer to Table 1 for the test results of the organosilicon linear product obtained in Example 2.

[0051] Comparative Example 1 The experimental process of Comparative Example 1 is the same as the operation process of Example 1, except for the following points: The hydrolyzate is not pretreated and directly undergoes preheating and subsequent flash evaporation and falling film evaporation. The chloride ion content of the hydrolyzate is 3 ppm. Refer to Table 1 for the test results of the organosilicon linear product obtained in Comparative Example 1.

[0052] Comparative Example 2 The experimental process of Comparative Example 2 is the same as the operation process of Example 2, except for the following points: The hydrolyzate is not pretreated and directly undergoes preheating and subsequent flash evaporation and falling film evaporation. The chloride ion content of the hydrolyzate is 3 ppm. Refer to Table 1 for the test results of the organosilicon linear product obtained in Comparative Example 2.

[0053]

Table 1

[0054] When the original chloride ion content of the hydrolyzate is 3 ppm or more, no matter how the temperature used for low-molecular-weight removal under reduced pressure is controlled, it was found in multiple batch experiments that the cyclic and linear forms were immediately separated without pretreatment. The obtained linear product had unstable properties, underwent a condensation reaction by itself, resulting in an increase in viscosity, an increase in the content of volatile components, and an increase in turbidity, so it did not meet the relevant quality specifications (the following tests).

[0055]

Table 2

[0056] When the chloride ion content of the hydrolyzate is reduced to 1 ppm or less by pretreatment, when the temperature for low-molecular-weight removal under reduced pressure is in the more preferable range of 220°C to 280°C, it was found in multiple batch experiments that a linear product that meets the relevant quality specifications (the following tests) can be obtained.

[0057]

Table 3

[0058] As can be seen from the experimental results, when the original chloride ion content of the hydrolyzate of dimethyldichlorosilane is 3 ppm or more, the physical properties of the obtained linear form become unstable, it is prone to undergo a condensation reaction by itself, the viscosity increases, the content of volatile substances increases, and the turbidity increases, so the product was not satisfactory. Conversely, when the chloride ion content of the hydrolyzate decreases, the low-molecular-weight removal of the hydrolyzate under reduced pressure can withstand a higher treatment temperature. The various indices of the obtained linear organosilicon form, in addition to the reduction of chlorine content, include the reduction of chromaticity, the content of volatile components is reduced to less than 1%, and the kinematic viscosity is controlled to be 120 mm 2 / s or less.

[0059] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the principles of the present invention shall be included within the scope of its protection.

Claims

1. A method for producing an organic silicon linear product, comprising: S1: a step of pretreating a hydrolyzate of dimethyldichlorosilane so that the chloride ion content in the hydrolyzate after pretreatment is 1 ppm or less; S2: a step of removing low-molecular substances from the hydrolyzate obtained by the pretreatment in step S1 under reduced pressure to separate an organic silicon cyclic body and an organic silicon linear body, wherein the removal of low-molecular substances under reduced pressure is carried out at a temperature of 190 to 280 ° C and a pressure ≤ -0.0955 MPa; A production method characterized by including the above.

2. In step S1, the hydrolyzate of dimethyldichlorosilane is fed to the pretreatment apparatus of step S1 at a flow rate of 3 to 15 m 3 / h, and the manufacturing method according to claim 1, characterized in that.

3. In step S1, first, a primary prefilter is used to remove mechanical impurities and colloids from the hydrolyzate, and then, a secondary treatment is performed using an activated carbon filter, a molecular sieve, and / or a resin to adsorb impurities of low-molecular substances containing chloride ions. The production method according to claim 1 or 2, characterized in that.

4. In step S2, the removal of low-molecular substances under reduced pressure is carried out in two stages; the first stage of the removal of low-molecular substances under reduced pressure has a temperature range of 220 to 280 ° C and a pressure ≤ -0.0955 MPa, and the second stage of the removal of low-molecular substances under reduced pressure has a temperature range of 240 to 280 ° C and a pressure ≤ -0.0955 MPa. The temperature of the second stage of the removal of low-molecular substances under reduced pressure is higher than the temperature of the first stage of the removal of low-molecular substances under reduced pressure. The production method according to claim 1 or 2, characterized in that.

5. In step S2, before removing low-molecular substances from the hydrolyzate under reduced pressure, the hydrolyzate obtained by the pretreatment in step S1 is heated to a temperature required for removing low-molecular substances under reduced pressure, and then put into a low-molecular substance removal device to carry out low-molecular substance removal under reduced pressure. The production method according to claim 1 or 2, characterized in that.

6. In steps S1 and S2, a step S11 of preheating the pretreated hydrolyzate is added; the pretreated hydrolyzate obtained in step S1 is first preheated in a heat exchange device, and the heat is provided from the cyclic body and / or linear body separated in step S2. The production method according to claim 1 or 2, characterized in that.

7. When the content of low-volatile components in the linear body obtained by removing low-molecular-weight components in step S2 exceeds 0.5%, step S2 is repeated using the material return pipeline until the content of low-volatile substances in the linear body becomes less than 0.5%, and then the linear body is discharged. The manufacturing method according to claim 1 or 2, characterized in that.

8. A manufacturing apparatus for the manufacturing method according to claim 1 or 2, characterized in that the apparatus comprises a pretreatment apparatus for the hydrolyzate of dimethyldichlorosilane and a vacuum low-molecular-weight removal apparatus.

9. A preheating device is installed between the pretreatment device and the vacuum low-molecular-weight removal device; A heat exchange device is installed between the pretreatment device and the preheating device, and the heat exchange device is connected to the gas outlet and / or liquid outlet of the vacuum low-molecular-weight removal device; When the gas outlet of the vacuum low-molecular-weight removal device is not connected to the heat exchange device, a condenser is connected immediately downstream of the gas outlet; when the gas outlet of the vacuum low-molecular-weight removal device is connected to the heat exchange device, the condenser is connected downstream of the gas discharge outlet of the heat exchange device; The condenser is connected to an annular body treatment device; The annular body treatment device is connected to an annular body storage device; When the liquid outlet of the vacuum low-molecular-weight removal device is not connected to the heat exchange device, a cooling device is connected immediately downstream of the liquid outlet; when the liquid outlet of the vacuum low-molecular-weight removal device is connected to the heat exchange device, the cooling device is connected downstream of the liquid discharge outlet of the heat exchange device; and The manufacturing apparatus according to claim 8, characterized in that the cooling device is connected to a linear body storage device.

10. The pretreatment device comprises a primary prefilter and a secondary treatment device; the primary prefilter removes mechanical impurities and colloids by filtration, and the secondary treatment device is an activated carbon filter, a molecular sieve, and / or a resin. The manufacturing apparatus according to claim 8, characterized in that.

11. The vacuum low-molecular-weight removal device is a two-stage vacuum low-molecular-weight removal device connected in series. The manufacturing apparatus according to claim 8, characterized in that.

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